xref: /linux/drivers/tty/n_gsm.c (revision fc5ced75d6dffc9e2a441520b7dc587b95281f86)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * n_gsm.c GSM 0710 tty multiplexor
4  * Copyright (c) 2009/10 Intel Corporation
5  * Copyright (c) 2022/23 Siemens Mobility GmbH
6  *
7  *	* THIS IS A DEVELOPMENT SNAPSHOT IT IS NOT A FINAL RELEASE *
8  *
9  * Outgoing path:
10  * tty -> DLCI fifo -> scheduler -> GSM MUX data queue    ---o-> ldisc
11  * control message               -> GSM MUX control queue --´
12  *
13  * Incoming path:
14  * ldisc -> gsm_queue() -o--> tty
15  *                        `-> gsm_control_response()
16  *
17  * TO DO:
18  *	Mostly done:	ioctls for setting modes/timing
19  *	Partly done:	hooks so you can pull off frames to non tty devs
20  *	Restart DLCI 0 when it closes ?
21  *	Improve the tx engine
22  *	Resolve tx side locking by adding a queue_head and routing
23  *		all control traffic via it
24  *	General tidy/document
25  *	Review the locking/move to refcounts more (mux now moved to an
26  *		alloc/free model ready)
27  *	Use newest tty open/close port helpers and install hooks
28  *	What to do about power functions ?
29  *	Termios setting and negotiation
30  *	Do we need a 'which mux are you' ioctl to correlate mux and tty sets
31  *
32  */
33 
34 #include <linux/types.h>
35 #include <linux/major.h>
36 #include <linux/errno.h>
37 #include <linux/signal.h>
38 #include <linux/fcntl.h>
39 #include <linux/sched/signal.h>
40 #include <linux/interrupt.h>
41 #include <linux/tty.h>
42 #include <linux/bitfield.h>
43 #include <linux/ctype.h>
44 #include <linux/mm.h>
45 #include <linux/math.h>
46 #include <linux/nospec.h>
47 #include <linux/string.h>
48 #include <linux/slab.h>
49 #include <linux/poll.h>
50 #include <linux/bitops.h>
51 #include <linux/file.h>
52 #include <linux/uaccess.h>
53 #include <linux/module.h>
54 #include <linux/timer.h>
55 #include <linux/tty_flip.h>
56 #include <linux/tty_driver.h>
57 #include <linux/serial.h>
58 #include <linux/kfifo.h>
59 #include <linux/skbuff.h>
60 #include <net/arp.h>
61 #include <linux/ip.h>
62 #include <linux/netdevice.h>
63 #include <linux/etherdevice.h>
64 #include <linux/gsmmux.h>
65 #include "tty.h"
66 
67 static int debug;
68 module_param(debug, int, 0600);
69 
70 /* Module debug bits */
71 #define DBG_DUMP	BIT(0) /* Data transmission dump. */
72 #define DBG_CD_ON	BIT(1) /* Always assume CD line on. */
73 #define DBG_DATA	BIT(2) /* Data transmission details. */
74 #define DBG_ERRORS	BIT(3) /* Details for fail conditions. */
75 #define DBG_TTY		BIT(4) /* Transmission statistics for DLCI TTYs. */
76 #define DBG_PAYLOAD	BIT(5) /* Limits DBG_DUMP to payload frames. */
77 
78 /* Defaults: these are from the specification */
79 
80 #define T1	10		/* 100mS */
81 #define T2	34		/* 333mS */
82 #define T3	10		/* 10s */
83 #define N2	3		/* Retry 3 times */
84 #define K	2		/* outstanding I frames */
85 
86 #define MAX_T3 255		/* In seconds. */
87 #define MAX_WINDOW_SIZE 7	/* Limit of K in error recovery mode. */
88 
89 /* Use long timers for testing at low speed with debug on */
90 #ifdef DEBUG_TIMING
91 #define T1	100
92 #define T2	200
93 #endif
94 
95 /*
96  * Semi-arbitrary buffer size limits. 0710 is normally run with 32-64 byte
97  * limits so this is plenty
98  */
99 #define MAX_MRU 1500
100 #define MAX_MTU 1500
101 #define MIN_MTU (PROT_OVERHEAD + 1)
102 /* SOF, ADDR, CTRL, LEN1, LEN2, ..., FCS, EOF */
103 #define PROT_OVERHEAD 7
104 #define	GSM_NET_TX_TIMEOUT (HZ*10)
105 
106 /*
107  *	struct gsm_mux_net	-	network interface
108  *
109  *	Created when net interface is initialized.
110  */
111 struct gsm_mux_net {
112 	struct kref ref;
113 	struct gsm_dlci *dlci;
114 };
115 
116 /*
117  *	Each block of data we have queued to go out is in the form of
118  *	a gsm_msg which holds everything we need in a link layer independent
119  *	format
120  */
121 
122 struct gsm_msg {
123 	struct list_head list;
124 	u8 addr;		/* DLCI address + flags */
125 	u8 ctrl;		/* Control byte + flags */
126 	unsigned int len;	/* Length of data block (can be zero) */
127 	u8 *data;	/* Points into buffer but not at the start */
128 	u8 buffer[];
129 };
130 
131 enum gsm_dlci_state {
132 	DLCI_CLOSED,
133 	DLCI_WAITING_CONFIG,	/* Waiting for DLCI configuration from user */
134 	DLCI_CONFIGURE,		/* Sending PN (for adaption > 1) */
135 	DLCI_OPENING,		/* Sending SABM not seen UA */
136 	DLCI_OPEN,		/* SABM/UA complete */
137 	DLCI_CLOSING,		/* Sending DISC not seen UA/DM */
138 };
139 
140 enum gsm_dlci_mode {
141 	DLCI_MODE_ABM,		/* Normal Asynchronous Balanced Mode */
142 	DLCI_MODE_ADM,		/* Asynchronous Disconnected Mode */
143 };
144 
145 /*
146  *	Each active data link has a gsm_dlci structure associated which ties
147  *	the link layer to an optional tty (if the tty side is open). To avoid
148  *	complexity right now these are only ever freed up when the mux is
149  *	shut down.
150  *
151  *	At the moment we don't free DLCI objects until the mux is torn down
152  *	this avoid object life time issues but might be worth review later.
153  */
154 
155 struct gsm_dlci {
156 	struct gsm_mux *gsm;
157 	int addr;
158 	enum gsm_dlci_state state;
159 	struct mutex mutex;
160 
161 	/* Link layer */
162 	enum gsm_dlci_mode mode;
163 	spinlock_t lock;	/* Protects the internal state */
164 	struct timer_list t1;	/* Retransmit timer for SABM and UA */
165 	int retries;
166 	/* Uplink tty if active */
167 	struct tty_port port;	/* The tty bound to this DLCI if there is one */
168 #define TX_SIZE		4096    /* Must be power of 2. */
169 	struct kfifo fifo;	/* Queue fifo for the DLCI */
170 	int adaption;		/* Adaption layer in use */
171 	int prev_adaption;
172 	u32 modem_rx;		/* Our incoming virtual modem lines */
173 	u32 modem_tx;		/* Our outgoing modem lines */
174 	unsigned int mtu;
175 	bool dead;		/* Refuse re-open */
176 	/* Configuration */
177 	u8 prio;		/* Priority */
178 	u8 ftype;		/* Frame type */
179 	u8 k;			/* Window size */
180 	/* Flow control */
181 	bool throttled;		/* Private copy of throttle state */
182 	bool constipated;	/* Throttle status for outgoing */
183 	/* Packetised I/O */
184 	struct sk_buff *skb;	/* Frame being sent */
185 	struct sk_buff_head skb_list;	/* Queued frames */
186 	/* Data handling callback */
187 	void (*data)(struct gsm_dlci *dlci, const u8 *data, int len);
188 	void (*prev_data)(struct gsm_dlci *dlci, const u8 *data, int len);
189 	struct net_device *net; /* network interface, if created */
190 };
191 
192 /*
193  * Parameter bits used for parameter negotiation according to 3GPP 27.010
194  * chapter 5.4.6.3.1.
195  */
196 
197 struct gsm_dlci_param_bits {
198 	u8 d_bits;
199 	u8 i_cl_bits;
200 	u8 p_bits;
201 	u8 t_bits;
202 	__le16 n_bits;
203 	u8 na_bits;
204 	u8 k_bits;
205 };
206 
207 static_assert(sizeof(struct gsm_dlci_param_bits) == 8);
208 
209 #define PN_D_FIELD_DLCI		GENMASK(5, 0)
210 #define PN_I_CL_FIELD_FTYPE	GENMASK(3, 0)
211 #define PN_I_CL_FIELD_ADAPTION	GENMASK(7, 4)
212 #define PN_P_FIELD_PRIO		GENMASK(5, 0)
213 #define PN_T_FIELD_T1		GENMASK(7, 0)
214 #define PN_N_FIELD_N1		GENMASK(15, 0)
215 #define PN_NA_FIELD_N2		GENMASK(7, 0)
216 #define PN_K_FIELD_K		GENMASK(2, 0)
217 
218 /* Total number of supported devices */
219 #define GSM_TTY_MINORS		256
220 
221 /* DLCI 0, 62/63 are special or reserved see gsmtty_open */
222 
223 #define NUM_DLCI		64
224 
225 /*
226  *	DLCI 0 is used to pass control blocks out of band of the data
227  *	flow (and with a higher link priority). One command can be outstanding
228  *	at a time and we use this structure to manage them. They are created
229  *	and destroyed by the user context, and updated by the receive paths
230  *	and timers
231  */
232 
233 struct gsm_control {
234 	u8 cmd;		/* Command we are issuing */
235 	u8 *data;	/* Data for the command in case we retransmit */
236 	int len;	/* Length of block for retransmission */
237 	int done;	/* Done flag */
238 	int error;	/* Error if any */
239 };
240 
241 enum gsm_encoding {
242 	GSM_BASIC_OPT,
243 	GSM_ADV_OPT,
244 };
245 
246 enum gsm_mux_state {
247 	GSM_SEARCH,
248 	GSM0_ADDRESS,
249 	GSM0_CONTROL,
250 	GSM0_LEN0,
251 	GSM0_LEN1,
252 	GSM0_DATA,
253 	GSM0_FCS,
254 	GSM0_SSOF,
255 	GSM1_START,
256 	GSM1_ADDRESS,
257 	GSM1_CONTROL,
258 	GSM1_DATA,
259 	GSM1_OVERRUN,
260 };
261 
262 /*
263  *	Each GSM mux we have is represented by this structure. If we are
264  *	operating as an ldisc then we use this structure as our ldisc
265  *	state. We need to sort out lifetimes and locking with respect
266  *	to the gsm mux array. For now we don't free DLCI objects that
267  *	have been instantiated until the mux itself is terminated.
268  *
269  *	To consider further: tty open versus mux shutdown.
270  */
271 
272 struct gsm_mux {
273 	struct tty_struct *tty;		/* The tty our ldisc is bound to */
274 	spinlock_t lock;
275 	struct mutex mutex;
276 	unsigned int num;
277 	struct kref ref;
278 
279 	/* Events on the GSM channel */
280 	wait_queue_head_t event;
281 
282 	/* ldisc send work */
283 	struct work_struct tx_work;
284 
285 	/* Bits for GSM mode decoding */
286 
287 	/* Framing Layer */
288 	u8 *buf;
289 	enum gsm_mux_state state;
290 	unsigned int len;
291 	unsigned int address;
292 	unsigned int count;
293 	bool escape;
294 	enum gsm_encoding encoding;
295 	u8 control;
296 	u8 fcs;
297 	u8 *txframe;			/* TX framing buffer */
298 
299 	/* Method for the receiver side */
300 	void (*receive)(struct gsm_mux *gsm, u8 ch);
301 
302 	/* Link Layer */
303 	unsigned int mru;
304 	unsigned int mtu;
305 	int initiator;			/* Did we initiate connection */
306 	bool dead;			/* Has the mux been shut down */
307 	struct gsm_dlci *dlci[NUM_DLCI];
308 	int old_c_iflag;		/* termios c_iflag value before attach */
309 	bool constipated;		/* Asked by remote to shut up */
310 	bool has_devices;		/* Devices were registered */
311 
312 	spinlock_t tx_lock;
313 	unsigned int tx_bytes;		/* TX data outstanding */
314 #define TX_THRESH_HI		8192
315 #define TX_THRESH_LO		2048
316 	struct list_head tx_ctrl_list;	/* Pending control packets */
317 	struct list_head tx_data_list;	/* Pending data packets */
318 
319 	/* Control messages */
320 	struct timer_list kick_timer;	/* Kick TX queuing on timeout */
321 	struct timer_list t2_timer;	/* Retransmit timer for commands */
322 	int cretries;			/* Command retry counter */
323 	struct gsm_control *pending_cmd;/* Our current pending command */
324 	spinlock_t control_lock;	/* Protects the pending command */
325 
326 	/* Keep-alive */
327 	struct timer_list ka_timer;	/* Keep-alive response timer */
328 	u8 ka_num;			/* Keep-alive match pattern */
329 	signed int ka_retries;		/* Keep-alive retry counter, -1 if not yet initialized */
330 
331 	/* Configuration */
332 	int adaption;		/* 1 or 2 supported */
333 	u8 ftype;		/* UI or UIH */
334 	int t1, t2;		/* Timers in 1/100th of a sec */
335 	unsigned int t3;	/* Power wake-up timer in seconds. */
336 	int n2;			/* Retry count */
337 	u8 k;			/* Window size */
338 	bool wait_config;	/* Wait for configuration by ioctl before DLCI open */
339 	u32 keep_alive;		/* Control channel keep-alive in 10ms */
340 
341 	/* Statistics (not currently exposed) */
342 	unsigned long bad_fcs;
343 	unsigned long malformed;
344 	unsigned long io_error;
345 	unsigned long open_error;
346 	unsigned long bad_size;
347 	unsigned long unsupported;
348 };
349 
350 
351 /*
352  *	Mux objects - needed so that we can translate a tty index into the
353  *	relevant mux and DLCI.
354  */
355 
356 #define MAX_MUX		4			/* 256 minors */
357 static struct gsm_mux *gsm_mux[MAX_MUX];	/* GSM muxes */
358 static DEFINE_SPINLOCK(gsm_mux_lock);
359 
360 static struct tty_driver *gsm_tty_driver;
361 
362 /*
363  *	This section of the driver logic implements the GSM encodings
364  *	both the basic and the 'advanced'. Reliable transport is not
365  *	supported.
366  */
367 
368 #define CR			0x02
369 #define EA			0x01
370 #define	PF			0x10
371 
372 /* I is special: the rest are ..*/
373 #define RR			0x01
374 #define UI			0x03
375 #define RNR			0x05
376 #define REJ			0x09
377 #define DM			0x0F
378 #define SABM			0x2F
379 #define DISC			0x43
380 #define UA			0x63
381 #define	UIH			0xEF
382 
383 /* Channel commands */
384 #define CMD_NSC			0x09
385 #define CMD_TEST		0x11
386 #define CMD_PSC			0x21
387 #define CMD_RLS			0x29
388 #define CMD_FCOFF		0x31
389 #define CMD_PN			0x41
390 #define CMD_RPN			0x49
391 #define CMD_FCON		0x51
392 #define CMD_CLD			0x61
393 #define CMD_SNC			0x69
394 #define CMD_MSC			0x71
395 
396 /* Virtual modem bits */
397 #define MDM_FC			0x01
398 #define MDM_RTC			0x02
399 #define MDM_RTR			0x04
400 #define MDM_IC			0x20
401 #define MDM_DV			0x40
402 
403 #define GSM0_SOF		0xF9
404 #define GSM1_SOF		0x7E
405 #define GSM1_ESCAPE		0x7D
406 #define GSM1_ESCAPE_BITS	0x20
407 #define XON			0x11
408 #define XOFF			0x13
409 #define ISO_IEC_646_MASK	0x7F
410 
411 static const struct tty_port_operations gsm_port_ops;
412 
413 /*
414  *	CRC table for GSM 0710
415  */
416 
417 static const u8 gsm_fcs8[256] = {
418 	0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75,
419 	0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B,
420 	0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69,
421 	0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67,
422 	0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D,
423 	0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43,
424 	0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51,
425 	0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F,
426 	0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05,
427 	0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B,
428 	0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19,
429 	0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17,
430 	0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D,
431 	0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33,
432 	0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21,
433 	0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F,
434 	0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95,
435 	0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B,
436 	0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89,
437 	0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87,
438 	0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD,
439 	0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3,
440 	0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1,
441 	0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF,
442 	0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5,
443 	0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB,
444 	0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9,
445 	0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7,
446 	0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD,
447 	0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3,
448 	0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1,
449 	0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF
450 };
451 
452 #define INIT_FCS	0xFF
453 #define GOOD_FCS	0xCF
454 
455 static void gsm_dlci_close(struct gsm_dlci *dlci);
456 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len);
457 static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk);
458 static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len,
459 								u8 ctrl);
460 static int gsm_send_packet(struct gsm_mux *gsm, struct gsm_msg *msg);
461 static struct gsm_dlci *gsm_dlci_alloc(struct gsm_mux *gsm, int addr);
462 static void gsmld_write_trigger(struct gsm_mux *gsm);
463 static void gsmld_write_task(struct work_struct *work);
464 
465 /**
466  *	gsm_fcs_add	-	update FCS
467  *	@fcs: Current FCS
468  *	@c: Next data
469  *
470  *	Update the FCS to include c. Uses the algorithm in the specification
471  *	notes.
472  */
473 
gsm_fcs_add(u8 fcs,u8 c)474 static inline u8 gsm_fcs_add(u8 fcs, u8 c)
475 {
476 	return gsm_fcs8[fcs ^ c];
477 }
478 
479 /**
480  *	gsm_fcs_add_block	-	update FCS for a block
481  *	@fcs: Current FCS
482  *	@c: buffer of data
483  *	@len: length of buffer
484  *
485  *	Update the FCS to include c. Uses the algorithm in the specification
486  *	notes.
487  */
488 
gsm_fcs_add_block(u8 fcs,u8 * c,int len)489 static inline u8 gsm_fcs_add_block(u8 fcs, u8 *c, int len)
490 {
491 	while (len--)
492 		fcs = gsm_fcs8[fcs ^ *c++];
493 	return fcs;
494 }
495 
496 /**
497  *	gsm_read_ea		-	read a byte into an EA
498  *	@val: variable holding value
499  *	@c: byte going into the EA
500  *
501  *	Processes one byte of an EA. Updates the passed variable
502  *	and returns 1 if the EA is now completely read
503  */
504 
gsm_read_ea(unsigned int * val,u8 c)505 static int gsm_read_ea(unsigned int *val, u8 c)
506 {
507 	/* Add the next 7 bits into the value */
508 	*val <<= 7;
509 	*val |= c >> 1;
510 	/* Was this the last byte of the EA 1 = yes*/
511 	return c & EA;
512 }
513 
514 /**
515  *	gsm_read_ea_val	-	read a value until EA
516  *	@val: variable holding value
517  *	@data: buffer of data
518  *	@dlen: length of data
519  *
520  *	Processes an EA value. Updates the passed variable and
521  *	returns the processed data length.
522  */
gsm_read_ea_val(unsigned int * val,const u8 * data,int dlen)523 static unsigned int gsm_read_ea_val(unsigned int *val, const u8 *data, int dlen)
524 {
525 	unsigned int len = 0;
526 
527 	for (; dlen > 0; dlen--) {
528 		len++;
529 		if (gsm_read_ea(val, *data++))
530 			break;
531 	}
532 	return len;
533 }
534 
535 /**
536  *	gsm_encode_modem	-	encode modem data bits
537  *	@dlci: DLCI to encode from
538  *
539  *	Returns the correct GSM encoded modem status bits (6 bit field) for
540  *	the current status of the DLCI and attached tty object
541  */
542 
gsm_encode_modem(const struct gsm_dlci * dlci)543 static u8 gsm_encode_modem(const struct gsm_dlci *dlci)
544 {
545 	u8 modembits = 0;
546 	/* FC is true flow control not modem bits */
547 	if (dlci->throttled)
548 		modembits |= MDM_FC;
549 	if (dlci->modem_tx & TIOCM_DTR)
550 		modembits |= MDM_RTC;
551 	if (dlci->modem_tx & TIOCM_RTS)
552 		modembits |= MDM_RTR;
553 	if (dlci->modem_tx & TIOCM_RI)
554 		modembits |= MDM_IC;
555 	if (dlci->modem_tx & TIOCM_CD || dlci->gsm->initiator)
556 		modembits |= MDM_DV;
557 	/* special mappings for passive side to operate as UE */
558 	if (dlci->modem_tx & TIOCM_OUT1)
559 		modembits |= MDM_IC;
560 	if (dlci->modem_tx & TIOCM_OUT2)
561 		modembits |= MDM_DV;
562 	return modembits;
563 }
564 
gsm_hex_dump_bytes(const char * fname,const u8 * data,unsigned long len)565 static void gsm_hex_dump_bytes(const char *fname, const u8 *data,
566 			       unsigned long len)
567 {
568 	char *prefix;
569 
570 	if (!fname) {
571 		print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE, 16, 1, data, len,
572 			       true);
573 		return;
574 	}
575 
576 	prefix = kasprintf(GFP_ATOMIC, "%s: ", fname);
577 	if (!prefix)
578 		return;
579 	print_hex_dump(KERN_INFO, prefix, DUMP_PREFIX_OFFSET, 16, 1, data, len,
580 		       true);
581 	kfree(prefix);
582 }
583 
584 /**
585  * gsm_encode_params	-	encode DLCI parameters
586  * @dlci: DLCI to encode from
587  * @params: buffer to fill with the encoded parameters
588  *
589  * Encodes the parameters according to GSM 07.10 section 5.4.6.3.1
590  * table 3.
591  */
gsm_encode_params(const struct gsm_dlci * dlci,struct gsm_dlci_param_bits * params)592 static int gsm_encode_params(const struct gsm_dlci *dlci,
593 			     struct gsm_dlci_param_bits *params)
594 {
595 	const struct gsm_mux *gsm = dlci->gsm;
596 	unsigned int i, cl;
597 
598 	switch (dlci->ftype) {
599 	case UIH:
600 		i = 0; /* UIH */
601 		break;
602 	case UI:
603 		i = 1; /* UI */
604 		break;
605 	default:
606 		pr_debug("unsupported frame type %d\n", dlci->ftype);
607 		return -EINVAL;
608 	}
609 
610 	switch (dlci->adaption) {
611 	case 1: /* Unstructured */
612 		cl = 0; /* convergence layer type 1 */
613 		break;
614 	case 2: /* Unstructured with modem bits. */
615 		cl = 1; /* convergence layer type 2 */
616 		break;
617 	default:
618 		pr_debug("unsupported adaption %d\n", dlci->adaption);
619 		return -EINVAL;
620 	}
621 
622 	params->d_bits = FIELD_PREP(PN_D_FIELD_DLCI, dlci->addr);
623 	/* UIH, convergence layer type 1 */
624 	params->i_cl_bits = FIELD_PREP(PN_I_CL_FIELD_FTYPE, i) |
625 			    FIELD_PREP(PN_I_CL_FIELD_ADAPTION, cl);
626 	params->p_bits = FIELD_PREP(PN_P_FIELD_PRIO, dlci->prio);
627 	params->t_bits = FIELD_PREP(PN_T_FIELD_T1, gsm->t1);
628 	params->n_bits = cpu_to_le16(FIELD_PREP(PN_N_FIELD_N1, dlci->mtu));
629 	params->na_bits = FIELD_PREP(PN_NA_FIELD_N2, gsm->n2);
630 	params->k_bits = FIELD_PREP(PN_K_FIELD_K, dlci->k);
631 
632 	return 0;
633 }
634 
635 /**
636  *	gsm_register_devices	-	register all tty devices for a given mux index
637  *
638  *	@driver: the tty driver that describes the tty devices
639  *	@index:  the mux number is used to calculate the minor numbers of the
640  *	         ttys for this mux and may differ from the position in the
641  *	         mux array.
642  */
gsm_register_devices(struct tty_driver * driver,unsigned int index)643 static int gsm_register_devices(struct tty_driver *driver, unsigned int index)
644 {
645 	struct device *dev;
646 	int i;
647 	unsigned int base;
648 
649 	if (!driver || index >= MAX_MUX)
650 		return -EINVAL;
651 
652 	base = index * NUM_DLCI; /* first minor for this index */
653 	for (i = 1; i < NUM_DLCI; i++) {
654 		/* Don't register device 0 - this is the control channel
655 		 * and not a usable tty interface
656 		 */
657 		dev = tty_register_device(gsm_tty_driver, base + i, NULL);
658 		if (IS_ERR(dev)) {
659 			if (debug & DBG_ERRORS)
660 				pr_info("%s failed to register device minor %u",
661 					__func__, base + i);
662 			for (i--; i >= 1; i--)
663 				tty_unregister_device(gsm_tty_driver, base + i);
664 			return PTR_ERR(dev);
665 		}
666 	}
667 
668 	return 0;
669 }
670 
671 /**
672  *	gsm_unregister_devices	-	unregister all tty devices for a given mux index
673  *
674  *	@driver: the tty driver that describes the tty devices
675  *	@index:  the mux number is used to calculate the minor numbers of the
676  *	         ttys for this mux and may differ from the position in the
677  *	         mux array.
678  */
gsm_unregister_devices(struct tty_driver * driver,unsigned int index)679 static void gsm_unregister_devices(struct tty_driver *driver,
680 				   unsigned int index)
681 {
682 	int i;
683 	unsigned int base;
684 
685 	if (!driver || index >= MAX_MUX)
686 		return;
687 
688 	base = index * NUM_DLCI; /* first minor for this index */
689 	for (i = 1; i < NUM_DLCI; i++) {
690 		/* Don't unregister device 0 - this is the control
691 		 * channel and not a usable tty interface
692 		 */
693 		tty_unregister_device(gsm_tty_driver, base + i);
694 	}
695 }
696 
697 /**
698  *	gsm_print_packet	-	display a frame for debug
699  *	@hdr: header to print before decode
700  *	@addr: address EA from the frame
701  *	@cr: C/R bit seen as initiator
702  *	@control: control including PF bit
703  *	@data: following data bytes
704  *	@dlen: length of data
705  *
706  *	Displays a packet in human readable format for debugging purposes. The
707  *	style is based on amateur radio LAP-B dump display.
708  */
709 
gsm_print_packet(const char * hdr,int addr,int cr,u8 control,const u8 * data,int dlen)710 static void gsm_print_packet(const char *hdr, int addr, int cr,
711 					u8 control, const u8 *data, int dlen)
712 {
713 	if (!(debug & DBG_DUMP))
714 		return;
715 	/* Only show user payload frames if debug & DBG_PAYLOAD */
716 	if (!(debug & DBG_PAYLOAD) && addr != 0)
717 		if ((control & ~PF) == UI || (control & ~PF) == UIH)
718 			return;
719 
720 	pr_info("%s %d) %c: ", hdr, addr, "RC"[cr]);
721 
722 	switch (control & ~PF) {
723 	case SABM:
724 		pr_cont("SABM");
725 		break;
726 	case UA:
727 		pr_cont("UA");
728 		break;
729 	case DISC:
730 		pr_cont("DISC");
731 		break;
732 	case DM:
733 		pr_cont("DM");
734 		break;
735 	case UI:
736 		pr_cont("UI");
737 		break;
738 	case UIH:
739 		pr_cont("UIH");
740 		break;
741 	default:
742 		if (!(control & 0x01)) {
743 			pr_cont("I N(S)%d N(R)%d",
744 				(control & 0x0E) >> 1, (control & 0xE0) >> 5);
745 		} else switch (control & 0x0F) {
746 			case RR:
747 				pr_cont("RR(%d)", (control & 0xE0) >> 5);
748 				break;
749 			case RNR:
750 				pr_cont("RNR(%d)", (control & 0xE0) >> 5);
751 				break;
752 			case REJ:
753 				pr_cont("REJ(%d)", (control & 0xE0) >> 5);
754 				break;
755 			default:
756 				pr_cont("[%02X]", control);
757 		}
758 	}
759 
760 	if (control & PF)
761 		pr_cont("(P)");
762 	else
763 		pr_cont("(F)");
764 
765 	gsm_hex_dump_bytes(NULL, data, dlen);
766 }
767 
768 
769 /*
770  *	Link level transmission side
771  */
772 
773 /**
774  *	gsm_stuff_frame	-	bytestuff a packet
775  *	@input: input buffer
776  *	@output: output buffer
777  *	@len: length of input
778  *
779  *	Expand a buffer by bytestuffing it. The worst case size change
780  *	is doubling and the caller is responsible for handing out
781  *	suitable sized buffers.
782  */
783 
gsm_stuff_frame(const u8 * input,u8 * output,int len)784 static int gsm_stuff_frame(const u8 *input, u8 *output, int len)
785 {
786 	int olen = 0;
787 	while (len--) {
788 		if (*input == GSM1_SOF || *input == GSM1_ESCAPE
789 		    || (*input & ISO_IEC_646_MASK) == XON
790 		    || (*input & ISO_IEC_646_MASK) == XOFF) {
791 			*output++ = GSM1_ESCAPE;
792 			*output++ = *input++ ^ GSM1_ESCAPE_BITS;
793 			olen++;
794 		} else
795 			*output++ = *input++;
796 		olen++;
797 	}
798 	return olen;
799 }
800 
801 /**
802  *	gsm_send	-	send a control frame
803  *	@gsm: our GSM mux
804  *	@addr: address for control frame
805  *	@cr: command/response bit seen as initiator
806  *	@control:  control byte including PF bit
807  *
808  *	Format up and transmit a control frame. These should be transmitted
809  *	ahead of data when they are needed.
810  */
gsm_send(struct gsm_mux * gsm,int addr,int cr,int control)811 static int gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
812 {
813 	struct gsm_msg *msg;
814 	u8 *dp;
815 	int ocr;
816 	unsigned long flags;
817 
818 	msg = gsm_data_alloc(gsm, addr, 0, control);
819 	if (!msg)
820 		return -ENOMEM;
821 
822 	/* toggle C/R coding if not initiator */
823 	ocr = cr ^ (gsm->initiator ? 0 : 1);
824 
825 	msg->data -= 3;
826 	dp = msg->data;
827 	*dp++ = (addr << 2) | (ocr << 1) | EA;
828 	*dp++ = control;
829 
830 	if (gsm->encoding == GSM_BASIC_OPT)
831 		*dp++ = EA; /* Length of data = 0 */
832 
833 	*dp = 0xFF - gsm_fcs_add_block(INIT_FCS, msg->data, dp - msg->data);
834 	msg->len = (dp - msg->data) + 1;
835 
836 	gsm_print_packet("Q->", addr, cr, control, NULL, 0);
837 
838 	spin_lock_irqsave(&gsm->tx_lock, flags);
839 	list_add_tail(&msg->list, &gsm->tx_ctrl_list);
840 	gsm->tx_bytes += msg->len;
841 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
842 	gsmld_write_trigger(gsm);
843 
844 	return 0;
845 }
846 
847 /**
848  *	gsm_dlci_clear_queues	-	remove outstanding data for a DLCI
849  *	@gsm: mux
850  *	@dlci: clear for this DLCI
851  *
852  *	Clears the data queues for a given DLCI.
853  */
gsm_dlci_clear_queues(struct gsm_mux * gsm,struct gsm_dlci * dlci)854 static void gsm_dlci_clear_queues(struct gsm_mux *gsm, struct gsm_dlci *dlci)
855 {
856 	struct gsm_msg *msg, *nmsg;
857 	int addr = dlci->addr;
858 	unsigned long flags;
859 
860 	/* Clear DLCI write fifo first */
861 	spin_lock_irqsave(&dlci->lock, flags);
862 	kfifo_reset(&dlci->fifo);
863 	spin_unlock_irqrestore(&dlci->lock, flags);
864 
865 	/* Clear data packets in MUX write queue */
866 	spin_lock_irqsave(&gsm->tx_lock, flags);
867 	list_for_each_entry_safe(msg, nmsg, &gsm->tx_data_list, list) {
868 		if (msg->addr != addr)
869 			continue;
870 		gsm->tx_bytes -= msg->len;
871 		list_del(&msg->list);
872 		kfree(msg);
873 	}
874 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
875 }
876 
877 /**
878  *	gsm_response	-	send a control response
879  *	@gsm: our GSM mux
880  *	@addr: address for control frame
881  *	@control:  control byte including PF bit
882  *
883  *	Format up and transmit a link level response frame.
884  */
885 
gsm_response(struct gsm_mux * gsm,int addr,int control)886 static inline void gsm_response(struct gsm_mux *gsm, int addr, int control)
887 {
888 	gsm_send(gsm, addr, 0, control);
889 }
890 
891 /**
892  *	gsm_command	-	send a control command
893  *	@gsm: our GSM mux
894  *	@addr: address for control frame
895  *	@control:  control byte including PF bit
896  *
897  *	Format up and transmit a link level command frame.
898  */
899 
gsm_command(struct gsm_mux * gsm,int addr,int control)900 static inline void gsm_command(struct gsm_mux *gsm, int addr, int control)
901 {
902 	gsm_send(gsm, addr, 1, control);
903 }
904 
905 /* Data transmission */
906 
907 #define HDR_LEN		6	/* ADDR CTRL [LEN.2] DATA FCS */
908 
909 /**
910  *	gsm_data_alloc		-	allocate data frame
911  *	@gsm: GSM mux
912  *	@addr: DLCI address
913  *	@len: length excluding header and FCS
914  *	@ctrl: control byte
915  *
916  *	Allocate a new data buffer for sending frames with data. Space is left
917  *	at the front for header bytes but that is treated as an implementation
918  *	detail and not for the high level code to use
919  */
920 
gsm_data_alloc(struct gsm_mux * gsm,u8 addr,int len,u8 ctrl)921 static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len,
922 								u8 ctrl)
923 {
924 	struct gsm_msg *m = kmalloc(sizeof(struct gsm_msg) + len + HDR_LEN,
925 								GFP_ATOMIC);
926 	if (m == NULL)
927 		return NULL;
928 	m->data = m->buffer + HDR_LEN - 1;	/* Allow for FCS */
929 	m->len = len;
930 	m->addr = addr;
931 	m->ctrl = ctrl;
932 	INIT_LIST_HEAD(&m->list);
933 	return m;
934 }
935 
936 /**
937  *	gsm_send_packet	-	sends a single packet
938  *	@gsm: GSM Mux
939  *	@msg: packet to send
940  *
941  *	The given packet is encoded and sent out. No memory is freed.
942  *	The caller must hold the gsm tx lock.
943  */
gsm_send_packet(struct gsm_mux * gsm,struct gsm_msg * msg)944 static int gsm_send_packet(struct gsm_mux *gsm, struct gsm_msg *msg)
945 {
946 	int len, ret;
947 
948 
949 	if (gsm->encoding == GSM_BASIC_OPT) {
950 		gsm->txframe[0] = GSM0_SOF;
951 		memcpy(gsm->txframe + 1, msg->data, msg->len);
952 		gsm->txframe[msg->len + 1] = GSM0_SOF;
953 		len = msg->len + 2;
954 	} else {
955 		gsm->txframe[0] = GSM1_SOF;
956 		len = gsm_stuff_frame(msg->data, gsm->txframe + 1, msg->len);
957 		gsm->txframe[len + 1] = GSM1_SOF;
958 		len += 2;
959 	}
960 
961 	if (debug & DBG_DATA)
962 		gsm_hex_dump_bytes(__func__, gsm->txframe, len);
963 	gsm_print_packet("-->", msg->addr, gsm->initiator, msg->ctrl, msg->data,
964 			 msg->len);
965 
966 	ret = gsmld_output(gsm, gsm->txframe, len);
967 	if (ret <= 0)
968 		return ret;
969 	/* FIXME: Can eliminate one SOF in many more cases */
970 	gsm->tx_bytes -= msg->len;
971 
972 	return 0;
973 }
974 
975 /**
976  *	gsm_is_flow_ctrl_msg	-	checks if flow control message
977  *	@msg: message to check
978  *
979  *	Returns true if the given message is a flow control command of the
980  *	control channel. False is returned in any other case.
981  */
gsm_is_flow_ctrl_msg(struct gsm_msg * msg)982 static bool gsm_is_flow_ctrl_msg(struct gsm_msg *msg)
983 {
984 	unsigned int cmd;
985 
986 	if (msg->addr > 0)
987 		return false;
988 
989 	switch (msg->ctrl & ~PF) {
990 	case UI:
991 	case UIH:
992 		cmd = 0;
993 		if (gsm_read_ea_val(&cmd, msg->data + 2, msg->len - 2) < 1)
994 			break;
995 		switch (cmd & ~PF) {
996 		case CMD_FCOFF:
997 		case CMD_FCON:
998 			return true;
999 		}
1000 		break;
1001 	}
1002 
1003 	return false;
1004 }
1005 
1006 /**
1007  *	gsm_data_kick	-	poke the queue
1008  *	@gsm: GSM Mux
1009  *
1010  *	The tty device has called us to indicate that room has appeared in
1011  *	the transmit queue. Ram more data into the pipe if we have any.
1012  *	If we have been flow-stopped by a CMD_FCOFF, then we can only
1013  *	send messages on DLCI0 until CMD_FCON. The caller must hold
1014  *	the gsm tx lock.
1015  */
gsm_data_kick(struct gsm_mux * gsm)1016 static int gsm_data_kick(struct gsm_mux *gsm)
1017 {
1018 	struct gsm_msg *msg, *nmsg;
1019 	struct gsm_dlci *dlci;
1020 	int ret;
1021 
1022 	clear_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
1023 
1024 	/* Serialize control messages and control channel messages first */
1025 	list_for_each_entry_safe(msg, nmsg, &gsm->tx_ctrl_list, list) {
1026 		if (gsm->constipated && !gsm_is_flow_ctrl_msg(msg))
1027 			continue;
1028 		ret = gsm_send_packet(gsm, msg);
1029 		switch (ret) {
1030 		case -ENOSPC:
1031 			return -ENOSPC;
1032 		case -ENODEV:
1033 			/* ldisc not open */
1034 			gsm->tx_bytes -= msg->len;
1035 			list_del(&msg->list);
1036 			kfree(msg);
1037 			continue;
1038 		default:
1039 			if (ret >= 0) {
1040 				list_del(&msg->list);
1041 				kfree(msg);
1042 			}
1043 			break;
1044 		}
1045 	}
1046 
1047 	if (gsm->constipated)
1048 		return -EAGAIN;
1049 
1050 	/* Serialize other channels */
1051 	if (list_empty(&gsm->tx_data_list))
1052 		return 0;
1053 	list_for_each_entry_safe(msg, nmsg, &gsm->tx_data_list, list) {
1054 		dlci = gsm->dlci[msg->addr];
1055 		/* Send only messages for DLCIs with valid state */
1056 		if (dlci->state != DLCI_OPEN) {
1057 			gsm->tx_bytes -= msg->len;
1058 			list_del(&msg->list);
1059 			kfree(msg);
1060 			continue;
1061 		}
1062 		ret = gsm_send_packet(gsm, msg);
1063 		switch (ret) {
1064 		case -ENOSPC:
1065 			return -ENOSPC;
1066 		case -ENODEV:
1067 			/* ldisc not open */
1068 			gsm->tx_bytes -= msg->len;
1069 			list_del(&msg->list);
1070 			kfree(msg);
1071 			continue;
1072 		default:
1073 			if (ret >= 0) {
1074 				list_del(&msg->list);
1075 				kfree(msg);
1076 			}
1077 			break;
1078 		}
1079 	}
1080 
1081 	return 1;
1082 }
1083 
1084 /**
1085  *	__gsm_data_queue		-	queue a UI or UIH frame
1086  *	@dlci: DLCI sending the data
1087  *	@msg: message queued
1088  *
1089  *	Add data to the transmit queue and try and get stuff moving
1090  *	out of the mux tty if not already doing so. The Caller must hold
1091  *	the gsm tx lock.
1092  */
1093 
__gsm_data_queue(struct gsm_dlci * dlci,struct gsm_msg * msg)1094 static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
1095 {
1096 	struct gsm_mux *gsm = dlci->gsm;
1097 	u8 *dp = msg->data;
1098 	u8 *fcs = dp + msg->len;
1099 
1100 	/* Fill in the header */
1101 	if (gsm->encoding == GSM_BASIC_OPT) {
1102 		if (msg->len < 128)
1103 			*--dp = (msg->len << 1) | EA;
1104 		else {
1105 			*--dp = (msg->len >> 7);	/* bits 7 - 15 */
1106 			*--dp = (msg->len & 127) << 1;	/* bits 0 - 6 */
1107 		}
1108 	}
1109 
1110 	*--dp = msg->ctrl;
1111 	if (gsm->initiator)
1112 		*--dp = (msg->addr << 2) | CR | EA;
1113 	else
1114 		*--dp = (msg->addr << 2) | EA;
1115 	*fcs = gsm_fcs_add_block(INIT_FCS, dp , msg->data - dp);
1116 	/* Ugly protocol layering violation */
1117 	if (msg->ctrl == UI || msg->ctrl == (UI|PF))
1118 		*fcs = gsm_fcs_add_block(*fcs, msg->data, msg->len);
1119 	*fcs = 0xFF - *fcs;
1120 
1121 	gsm_print_packet("Q> ", msg->addr, gsm->initiator, msg->ctrl,
1122 							msg->data, msg->len);
1123 
1124 	/* Move the header back and adjust the length, also allow for the FCS
1125 	   now tacked on the end */
1126 	msg->len += (msg->data - dp) + 1;
1127 	msg->data = dp;
1128 
1129 	/* Add to the actual output queue */
1130 	switch (msg->ctrl & ~PF) {
1131 	case UI:
1132 	case UIH:
1133 		if (msg->addr > 0) {
1134 			list_add_tail(&msg->list, &gsm->tx_data_list);
1135 			break;
1136 		}
1137 		fallthrough;
1138 	default:
1139 		list_add_tail(&msg->list, &gsm->tx_ctrl_list);
1140 		break;
1141 	}
1142 	gsm->tx_bytes += msg->len;
1143 
1144 	gsmld_write_trigger(gsm);
1145 	mod_timer(&gsm->kick_timer, jiffies + 10 * gsm->t1 * HZ / 100);
1146 }
1147 
1148 /**
1149  *	gsm_data_queue		-	queue a UI or UIH frame
1150  *	@dlci: DLCI sending the data
1151  *	@msg: message queued
1152  *
1153  *	Add data to the transmit queue and try and get stuff moving
1154  *	out of the mux tty if not already doing so. Take the
1155  *	the gsm tx lock and dlci lock.
1156  */
1157 
gsm_data_queue(struct gsm_dlci * dlci,struct gsm_msg * msg)1158 static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
1159 {
1160 	unsigned long flags;
1161 	spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
1162 	__gsm_data_queue(dlci, msg);
1163 	spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
1164 }
1165 
1166 /**
1167  *	gsm_dlci_data_output	-	try and push data out of a DLCI
1168  *	@gsm: mux
1169  *	@dlci: the DLCI to pull data from
1170  *
1171  *	Pull data from a DLCI and send it into the transmit queue if there
1172  *	is data. Keep to the MRU of the mux. This path handles the usual tty
1173  *	interface which is a byte stream with optional modem data.
1174  *
1175  *	Caller must hold the tx_lock of the mux.
1176  */
1177 
gsm_dlci_data_output(struct gsm_mux * gsm,struct gsm_dlci * dlci)1178 static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
1179 {
1180 	struct gsm_msg *msg;
1181 	u8 *dp;
1182 	int h, len, size;
1183 
1184 	/* for modem bits without break data */
1185 	h = ((dlci->adaption == 1) ? 0 : 1);
1186 
1187 	len = kfifo_len(&dlci->fifo);
1188 	if (len == 0)
1189 		return 0;
1190 
1191 	/* MTU/MRU count only the data bits but watch adaption mode */
1192 	if ((len + h) > dlci->mtu)
1193 		len = dlci->mtu - h;
1194 
1195 	size = len + h;
1196 
1197 	msg = gsm_data_alloc(gsm, dlci->addr, size, dlci->ftype);
1198 	if (!msg)
1199 		return -ENOMEM;
1200 	dp = msg->data;
1201 	switch (dlci->adaption) {
1202 	case 1: /* Unstructured */
1203 		break;
1204 	case 2: /* Unstructured with modem bits.
1205 		 * Always one byte as we never send inline break data
1206 		 */
1207 		*dp++ = (gsm_encode_modem(dlci) << 1) | EA;
1208 		break;
1209 	default:
1210 		pr_err("%s: unsupported adaption %d\n", __func__,
1211 		       dlci->adaption);
1212 		break;
1213 	}
1214 
1215 	WARN_ON(len != kfifo_out_locked(&dlci->fifo, dp, len,
1216 		&dlci->lock));
1217 
1218 	/* Notify upper layer about available send space. */
1219 	tty_port_tty_wakeup(&dlci->port);
1220 
1221 	__gsm_data_queue(dlci, msg);
1222 	/* Bytes of data we used up */
1223 	return size;
1224 }
1225 
1226 /**
1227  *	gsm_dlci_data_output_framed  -	try and push data out of a DLCI
1228  *	@gsm: mux
1229  *	@dlci: the DLCI to pull data from
1230  *
1231  *	Pull data from a DLCI and send it into the transmit queue if there
1232  *	is data. Keep to the MRU of the mux. This path handles framed data
1233  *	queued as skbuffs to the DLCI.
1234  *
1235  *	Caller must hold the tx_lock of the mux.
1236  */
1237 
gsm_dlci_data_output_framed(struct gsm_mux * gsm,struct gsm_dlci * dlci)1238 static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
1239 						struct gsm_dlci *dlci)
1240 {
1241 	struct gsm_msg *msg;
1242 	u8 *dp;
1243 	int len, size;
1244 	int last = 0, first = 0;
1245 	int overhead = 0;
1246 
1247 	/* One byte per frame is used for B/F flags */
1248 	if (dlci->adaption == 4)
1249 		overhead = 1;
1250 
1251 	/* dlci->skb is locked by tx_lock */
1252 	if (dlci->skb == NULL) {
1253 		dlci->skb = skb_dequeue_tail(&dlci->skb_list);
1254 		if (dlci->skb == NULL)
1255 			return 0;
1256 		first = 1;
1257 	}
1258 	len = dlci->skb->len + overhead;
1259 
1260 	/* MTU/MRU count only the data bits */
1261 	if (len > dlci->mtu) {
1262 		if (dlci->adaption == 3) {
1263 			/* Over long frame, bin it */
1264 			dev_kfree_skb_any(dlci->skb);
1265 			dlci->skb = NULL;
1266 			return 0;
1267 		}
1268 		len = dlci->mtu;
1269 	} else
1270 		last = 1;
1271 
1272 	size = len + overhead;
1273 	msg = gsm_data_alloc(gsm, dlci->addr, size, dlci->ftype);
1274 	if (msg == NULL) {
1275 		skb_queue_tail(&dlci->skb_list, dlci->skb);
1276 		dlci->skb = NULL;
1277 		return -ENOMEM;
1278 	}
1279 	dp = msg->data;
1280 
1281 	if (dlci->adaption == 4) { /* Interruptible framed (Packetised Data) */
1282 		/* Flag byte to carry the start/end info */
1283 		*dp++ = last << 7 | first << 6 | 1;	/* EA */
1284 		len--;
1285 	}
1286 	memcpy(dp, dlci->skb->data, len);
1287 	skb_pull(dlci->skb, len);
1288 	__gsm_data_queue(dlci, msg);
1289 	if (last) {
1290 		dev_kfree_skb_any(dlci->skb);
1291 		dlci->skb = NULL;
1292 	}
1293 	return size;
1294 }
1295 
1296 /**
1297  *	gsm_dlci_modem_output	-	try and push modem status out of a DLCI
1298  *	@gsm: mux
1299  *	@dlci: the DLCI to pull modem status from
1300  *	@brk: break signal
1301  *
1302  *	Push an empty frame in to the transmit queue to update the modem status
1303  *	bits and to transmit an optional break.
1304  *
1305  *	Caller must hold the tx_lock of the mux.
1306  */
1307 
gsm_dlci_modem_output(struct gsm_mux * gsm,struct gsm_dlci * dlci,u8 brk)1308 static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci,
1309 				 u8 brk)
1310 {
1311 	u8 *dp = NULL;
1312 	struct gsm_msg *msg;
1313 	int size = 0;
1314 
1315 	/* for modem bits without break data */
1316 	switch (dlci->adaption) {
1317 	case 1: /* Unstructured */
1318 		break;
1319 	case 2: /* Unstructured with modem bits. */
1320 		size++;
1321 		if (brk > 0)
1322 			size++;
1323 		break;
1324 	default:
1325 		pr_err("%s: unsupported adaption %d\n", __func__,
1326 		       dlci->adaption);
1327 		return -EINVAL;
1328 	}
1329 
1330 	msg = gsm_data_alloc(gsm, dlci->addr, size, dlci->ftype);
1331 	if (!msg) {
1332 		pr_err("%s: gsm_data_alloc error", __func__);
1333 		return -ENOMEM;
1334 	}
1335 	dp = msg->data;
1336 	switch (dlci->adaption) {
1337 	case 1: /* Unstructured */
1338 		break;
1339 	case 2: /* Unstructured with modem bits. */
1340 		if (brk == 0) {
1341 			*dp++ = (gsm_encode_modem(dlci) << 1) | EA;
1342 		} else {
1343 			*dp++ = gsm_encode_modem(dlci) << 1;
1344 			*dp++ = (brk << 4) | 2 | EA; /* Length, Break, EA */
1345 		}
1346 		break;
1347 	default:
1348 		/* Handled above */
1349 		break;
1350 	}
1351 
1352 	__gsm_data_queue(dlci, msg);
1353 	return size;
1354 }
1355 
1356 /**
1357  *	gsm_dlci_data_sweep		-	look for data to send
1358  *	@gsm: the GSM mux
1359  *
1360  *	Sweep the GSM mux channels in priority order looking for ones with
1361  *	data to send. We could do with optimising this scan a bit. We aim
1362  *	to fill the queue totally or up to TX_THRESH_HI bytes. Once we hit
1363  *	TX_THRESH_LO we get called again
1364  *
1365  *	FIXME: We should round robin between groups and in theory you can
1366  *	renegotiate DLCI priorities with optional stuff. Needs optimising.
1367  */
1368 
gsm_dlci_data_sweep(struct gsm_mux * gsm)1369 static int gsm_dlci_data_sweep(struct gsm_mux *gsm)
1370 {
1371 	/* Priority ordering: We should do priority with RR of the groups */
1372 	int i, len, ret = 0;
1373 	bool sent;
1374 	struct gsm_dlci *dlci;
1375 
1376 	while (gsm->tx_bytes < TX_THRESH_HI) {
1377 		for (sent = false, i = 1; i < NUM_DLCI; i++) {
1378 			dlci = gsm->dlci[i];
1379 			/* skip unused or blocked channel */
1380 			if (!dlci || dlci->constipated)
1381 				continue;
1382 			/* skip channels with invalid state */
1383 			if (dlci->state != DLCI_OPEN)
1384 				continue;
1385 			/* count the sent data per adaption */
1386 			if (dlci->adaption < 3 && !dlci->net)
1387 				len = gsm_dlci_data_output(gsm, dlci);
1388 			else
1389 				len = gsm_dlci_data_output_framed(gsm, dlci);
1390 			/* on error exit */
1391 			if (len < 0)
1392 				return ret;
1393 			if (len > 0) {
1394 				ret++;
1395 				sent = true;
1396 				/* The lower DLCs can starve the higher DLCs! */
1397 				break;
1398 			}
1399 			/* try next */
1400 		}
1401 		if (!sent)
1402 			break;
1403 	}
1404 
1405 	return ret;
1406 }
1407 
1408 /**
1409  *	gsm_dlci_data_kick	-	transmit if possible
1410  *	@dlci: DLCI to kick
1411  *
1412  *	Transmit data from this DLCI if the queue is empty. We can't rely on
1413  *	a tty wakeup except when we filled the pipe so we need to fire off
1414  *	new data ourselves in other cases.
1415  */
1416 
gsm_dlci_data_kick(struct gsm_dlci * dlci)1417 static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
1418 {
1419 	unsigned long flags;
1420 	int sweep;
1421 
1422 	if (dlci->constipated)
1423 		return;
1424 
1425 	spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
1426 	/* If we have nothing running then we need to fire up */
1427 	sweep = (dlci->gsm->tx_bytes < TX_THRESH_LO);
1428 	if (dlci->gsm->tx_bytes == 0) {
1429 		if (dlci->net)
1430 			gsm_dlci_data_output_framed(dlci->gsm, dlci);
1431 		else
1432 			gsm_dlci_data_output(dlci->gsm, dlci);
1433 	}
1434 	if (sweep)
1435 		gsm_dlci_data_sweep(dlci->gsm);
1436 	spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
1437 }
1438 
1439 /*
1440  *	Control message processing
1441  */
1442 
1443 
1444 /**
1445  * gsm_control_command	-	send a command frame to a control
1446  * @gsm: gsm channel
1447  * @cmd: the command to use
1448  * @data: data to follow encoded info
1449  * @dlen: length of data
1450  *
1451  * Encode up and queue a UI/UIH frame containing our command.
1452  */
gsm_control_command(struct gsm_mux * gsm,int cmd,const u8 * data,int dlen)1453 static int gsm_control_command(struct gsm_mux *gsm, int cmd, const u8 *data,
1454 			       int dlen)
1455 {
1456 	struct gsm_msg *msg;
1457 	struct gsm_dlci *dlci = gsm->dlci[0];
1458 
1459 	msg = gsm_data_alloc(gsm, 0, dlen + 2, dlci->ftype);
1460 	if (msg == NULL)
1461 		return -ENOMEM;
1462 
1463 	msg->data[0] = (cmd << 1) | CR | EA;	/* Set C/R */
1464 	msg->data[1] = (dlen << 1) | EA;
1465 	memcpy(msg->data + 2, data, dlen);
1466 	gsm_data_queue(dlci, msg);
1467 
1468 	return 0;
1469 }
1470 
1471 /**
1472  *	gsm_control_reply	-	send a response frame to a control
1473  *	@gsm: gsm channel
1474  *	@cmd: the command to use
1475  *	@data: data to follow encoded info
1476  *	@dlen: length of data
1477  *
1478  *	Encode up and queue a UI/UIH frame containing our response.
1479  */
1480 
gsm_control_reply(struct gsm_mux * gsm,int cmd,const u8 * data,int dlen)1481 static void gsm_control_reply(struct gsm_mux *gsm, int cmd, const u8 *data,
1482 					int dlen)
1483 {
1484 	struct gsm_msg *msg;
1485 	struct gsm_dlci *dlci = gsm->dlci[0];
1486 
1487 	msg = gsm_data_alloc(gsm, 0, dlen + 2, dlci->ftype);
1488 	if (msg == NULL)
1489 		return;
1490 	msg->data[0] = (cmd & 0xFE) << 1 | EA;	/* Clear C/R */
1491 	msg->data[1] = (dlen << 1) | EA;
1492 	memcpy(msg->data + 2, data, dlen);
1493 	gsm_data_queue(dlci, msg);
1494 }
1495 
1496 /**
1497  *	gsm_process_modem	-	process received modem status
1498  *	@tty: virtual tty bound to the DLCI
1499  *	@dlci: DLCI to affect
1500  *	@modem: modem bits (full EA)
1501  *	@slen: number of signal octets
1502  *
1503  *	Used when a modem control message or line state inline in adaption
1504  *	layer 2 is processed. Sort out the local modem state and throttles
1505  */
1506 
gsm_process_modem(struct tty_struct * tty,struct gsm_dlci * dlci,u32 modem,int slen)1507 static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
1508 							u32 modem, int slen)
1509 {
1510 	int  mlines = 0;
1511 	u8 brk = 0;
1512 	int fc;
1513 
1514 	/* The modem status command can either contain one octet (V.24 signals)
1515 	 * or two octets (V.24 signals + break signals). This is specified in
1516 	 * section 5.4.6.3.7 of the 07.10 mux spec.
1517 	 */
1518 
1519 	if (slen == 1)
1520 		modem = modem & 0x7f;
1521 	else {
1522 		brk = modem & 0x7f;
1523 		modem = (modem >> 7) & 0x7f;
1524 	}
1525 
1526 	/* Flow control/ready to communicate */
1527 	fc = (modem & MDM_FC) || !(modem & MDM_RTR);
1528 	if (fc && !dlci->constipated) {
1529 		/* Need to throttle our output on this device */
1530 		dlci->constipated = true;
1531 	} else if (!fc && dlci->constipated) {
1532 		dlci->constipated = false;
1533 		gsm_dlci_data_kick(dlci);
1534 	}
1535 
1536 	/* Map modem bits */
1537 	if (modem & MDM_RTC)
1538 		mlines |= TIOCM_DSR | TIOCM_DTR;
1539 	if (modem & MDM_RTR)
1540 		mlines |= TIOCM_RTS | TIOCM_CTS;
1541 	if (modem & MDM_IC)
1542 		mlines |= TIOCM_RI;
1543 	if (modem & MDM_DV)
1544 		mlines |= TIOCM_CD;
1545 
1546 	/* Carrier drop -> hangup */
1547 	if (tty) {
1548 		if ((mlines & TIOCM_CD) == 0 && (dlci->modem_rx & TIOCM_CD))
1549 			if (!C_CLOCAL(tty))
1550 				tty_hangup(tty);
1551 	}
1552 	if (brk & 0x01)
1553 		tty_insert_flip_char(&dlci->port, 0, TTY_BREAK);
1554 	dlci->modem_rx = mlines;
1555 	wake_up_interruptible(&dlci->gsm->event);
1556 }
1557 
1558 /**
1559  * gsm_process_negotiation	-	process received parameters
1560  * @gsm: GSM channel
1561  * @addr: DLCI address
1562  * @cr: command/response
1563  * @params: encoded parameters from the parameter negotiation message
1564  *
1565  * Used when the response for our parameter negotiation command was
1566  * received.
1567  */
gsm_process_negotiation(struct gsm_mux * gsm,unsigned int addr,unsigned int cr,const struct gsm_dlci_param_bits * params)1568 static int gsm_process_negotiation(struct gsm_mux *gsm, unsigned int addr,
1569 				   unsigned int cr,
1570 				   const struct gsm_dlci_param_bits *params)
1571 {
1572 	struct gsm_dlci *dlci = gsm->dlci[addr];
1573 	unsigned int ftype, i, adaption, prio, n1, k;
1574 
1575 	i = FIELD_GET(PN_I_CL_FIELD_FTYPE, params->i_cl_bits);
1576 	adaption = FIELD_GET(PN_I_CL_FIELD_ADAPTION, params->i_cl_bits) + 1;
1577 	prio = FIELD_GET(PN_P_FIELD_PRIO, params->p_bits);
1578 	n1 = FIELD_GET(PN_N_FIELD_N1, get_unaligned_le16(&params->n_bits));
1579 	k = FIELD_GET(PN_K_FIELD_K, params->k_bits);
1580 
1581 	if (n1 < MIN_MTU) {
1582 		if (debug & DBG_ERRORS)
1583 			pr_info("%s N1 out of range in PN\n", __func__);
1584 		return -EINVAL;
1585 	}
1586 
1587 	switch (i) {
1588 	case 0x00:
1589 		ftype = UIH;
1590 		break;
1591 	case 0x01:
1592 		ftype = UI;
1593 		break;
1594 	case 0x02: /* I frames are not supported */
1595 		if (debug & DBG_ERRORS)
1596 			pr_info("%s unsupported I frame request in PN\n",
1597 				__func__);
1598 		gsm->unsupported++;
1599 		return -EINVAL;
1600 	default:
1601 		if (debug & DBG_ERRORS)
1602 			pr_info("%s i out of range in PN\n", __func__);
1603 		return -EINVAL;
1604 	}
1605 
1606 	if (!cr && gsm->initiator) {
1607 		if (adaption != dlci->adaption) {
1608 			if (debug & DBG_ERRORS)
1609 				pr_info("%s invalid adaption %d in PN\n",
1610 					__func__, adaption);
1611 			return -EINVAL;
1612 		}
1613 		if (prio != dlci->prio) {
1614 			if (debug & DBG_ERRORS)
1615 				pr_info("%s invalid priority %d in PN",
1616 					__func__, prio);
1617 			return -EINVAL;
1618 		}
1619 		if (n1 > gsm->mru || n1 > dlci->mtu) {
1620 			/* We requested a frame size but the other party wants
1621 			 * to send larger frames. The standard allows only a
1622 			 * smaller response value than requested (5.4.6.3.1).
1623 			 */
1624 			if (debug & DBG_ERRORS)
1625 				pr_info("%s invalid N1 %d in PN\n", __func__,
1626 					n1);
1627 			return -EINVAL;
1628 		}
1629 		dlci->mtu = n1;
1630 		if (ftype != dlci->ftype) {
1631 			if (debug & DBG_ERRORS)
1632 				pr_info("%s invalid i %d in PN\n", __func__, i);
1633 			return -EINVAL;
1634 		}
1635 		if (ftype != UI && ftype != UIH && k > dlci->k) {
1636 			if (debug & DBG_ERRORS)
1637 				pr_info("%s invalid k %d in PN\n", __func__, k);
1638 			return -EINVAL;
1639 		}
1640 		dlci->k = k;
1641 	} else if (cr && !gsm->initiator) {
1642 		/* Only convergence layer type 1 and 2 are supported. */
1643 		if (adaption != 1 && adaption != 2) {
1644 			if (debug & DBG_ERRORS)
1645 				pr_info("%s invalid adaption %d in PN\n",
1646 					__func__, adaption);
1647 			return -EINVAL;
1648 		}
1649 		dlci->adaption = adaption;
1650 		if (n1 > gsm->mru) {
1651 			/* Propose a smaller value */
1652 			dlci->mtu = gsm->mru;
1653 		} else if (n1 > MAX_MTU) {
1654 			/* Propose a smaller value */
1655 			dlci->mtu = MAX_MTU;
1656 		} else {
1657 			dlci->mtu = n1;
1658 		}
1659 		dlci->prio = prio;
1660 		dlci->ftype = ftype;
1661 		dlci->k = k;
1662 	} else {
1663 		return -EINVAL;
1664 	}
1665 
1666 	return 0;
1667 }
1668 
1669 /**
1670  *	gsm_control_modem	-	modem status received
1671  *	@gsm: GSM channel
1672  *	@data: data following command
1673  *	@clen: command length
1674  *
1675  *	We have received a modem status control message. This is used by
1676  *	the GSM mux protocol to pass virtual modem line status and optionally
1677  *	to indicate break signals. Unpack it, convert to Linux representation
1678  *	and if need be stuff a break message down the tty.
1679  */
1680 
gsm_control_modem(struct gsm_mux * gsm,const u8 * data,int clen)1681 static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
1682 {
1683 	unsigned int addr = 0;
1684 	unsigned int modem = 0;
1685 	struct gsm_dlci *dlci;
1686 	int len = clen;
1687 	int cl = clen;
1688 	const u8 *dp = data;
1689 	struct tty_struct *tty;
1690 
1691 	len = gsm_read_ea_val(&addr, data, cl);
1692 	if (len < 1)
1693 		return;
1694 
1695 	addr >>= 1;
1696 	/* Closed port, or invalid ? */
1697 	if (addr == 0 || addr >= NUM_DLCI || gsm->dlci[addr] == NULL)
1698 		return;
1699 	dlci = gsm->dlci[addr];
1700 
1701 	/* Must be at least one byte following the EA */
1702 	if ((cl - len) < 1)
1703 		return;
1704 
1705 	dp += len;
1706 	cl -= len;
1707 
1708 	/* get the modem status */
1709 	len = gsm_read_ea_val(&modem, dp, cl);
1710 	if (len < 1)
1711 		return;
1712 
1713 	tty = tty_port_tty_get(&dlci->port);
1714 	gsm_process_modem(tty, dlci, modem, cl);
1715 	if (tty) {
1716 		tty_wakeup(tty);
1717 		tty_kref_put(tty);
1718 	}
1719 	gsm_control_reply(gsm, CMD_MSC, data, clen);
1720 }
1721 
1722 /**
1723  * gsm_control_negotiation	-	parameter negotiation received
1724  * @gsm: GSM channel
1725  * @cr: command/response flag
1726  * @data: data following command
1727  * @dlen: data length
1728  *
1729  * We have received a parameter negotiation message. This is used by
1730  * the GSM mux protocol to configure protocol parameters for a new DLCI.
1731  */
gsm_control_negotiation(struct gsm_mux * gsm,unsigned int cr,const u8 * data,unsigned int dlen)1732 static void gsm_control_negotiation(struct gsm_mux *gsm, unsigned int cr,
1733 				    const u8 *data, unsigned int dlen)
1734 {
1735 	unsigned int addr;
1736 	struct gsm_dlci_param_bits pn_reply;
1737 	struct gsm_dlci *dlci;
1738 	struct gsm_dlci_param_bits *params;
1739 
1740 	if (dlen < sizeof(struct gsm_dlci_param_bits)) {
1741 		gsm->open_error++;
1742 		return;
1743 	}
1744 
1745 	/* Invalid DLCI? */
1746 	params = (struct gsm_dlci_param_bits *)data;
1747 	addr = FIELD_GET(PN_D_FIELD_DLCI, params->d_bits);
1748 	if (addr == 0 || addr >= NUM_DLCI || !gsm->dlci[addr]) {
1749 		gsm->open_error++;
1750 		return;
1751 	}
1752 	dlci = gsm->dlci[addr];
1753 
1754 	/* Too late for parameter negotiation? */
1755 	if ((!cr && dlci->state == DLCI_OPENING) || dlci->state == DLCI_OPEN) {
1756 		gsm->open_error++;
1757 		return;
1758 	}
1759 
1760 	/* Process the received parameters */
1761 	if (gsm_process_negotiation(gsm, addr, cr, params) != 0) {
1762 		/* Negotiation failed. Close the link. */
1763 		if (debug & DBG_ERRORS)
1764 			pr_info("%s PN failed\n", __func__);
1765 		gsm->open_error++;
1766 		gsm_dlci_close(dlci);
1767 		return;
1768 	}
1769 
1770 	if (cr) {
1771 		/* Reply command with accepted parameters. */
1772 		if (gsm_encode_params(dlci, &pn_reply) == 0)
1773 			gsm_control_reply(gsm, CMD_PN, (const u8 *)&pn_reply,
1774 					  sizeof(pn_reply));
1775 		else if (debug & DBG_ERRORS)
1776 			pr_info("%s PN invalid\n", __func__);
1777 	} else if (dlci->state == DLCI_CONFIGURE) {
1778 		/* Proceed with link setup by sending SABM before UA */
1779 		dlci->state = DLCI_OPENING;
1780 		gsm_command(gsm, dlci->addr, SABM|PF);
1781 		mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
1782 	} else {
1783 		if (debug & DBG_ERRORS)
1784 			pr_info("%s PN in invalid state\n", __func__);
1785 		gsm->open_error++;
1786 	}
1787 }
1788 
1789 /**
1790  *	gsm_control_rls		-	remote line status
1791  *	@gsm: GSM channel
1792  *	@data: data bytes
1793  *	@clen: data length
1794  *
1795  *	The modem sends us a two byte message on the control channel whenever
1796  *	it wishes to send us an error state from the virtual link. Stuff
1797  *	this into the uplink tty if present
1798  */
1799 
gsm_control_rls(struct gsm_mux * gsm,const u8 * data,int clen)1800 static void gsm_control_rls(struct gsm_mux *gsm, const u8 *data, int clen)
1801 {
1802 	struct tty_port *port;
1803 	unsigned int addr = 0;
1804 	u8 bits;
1805 	int len = clen;
1806 	const u8 *dp = data;
1807 
1808 	while (gsm_read_ea(&addr, *dp++) == 0) {
1809 		len--;
1810 		if (len == 0)
1811 			return;
1812 	}
1813 	/* Must be at least one byte following ea */
1814 	len--;
1815 	if (len <= 0)
1816 		return;
1817 	addr >>= 1;
1818 	/* Closed port, or invalid ? */
1819 	if (addr == 0 || addr >= NUM_DLCI || gsm->dlci[addr] == NULL)
1820 		return;
1821 	/* No error ? */
1822 	bits = *dp;
1823 	if ((bits & 1) == 0)
1824 		return;
1825 
1826 	port = &gsm->dlci[addr]->port;
1827 
1828 	if (bits & 2)
1829 		tty_insert_flip_char(port, 0, TTY_OVERRUN);
1830 	if (bits & 4)
1831 		tty_insert_flip_char(port, 0, TTY_PARITY);
1832 	if (bits & 8)
1833 		tty_insert_flip_char(port, 0, TTY_FRAME);
1834 
1835 	tty_flip_buffer_push(port);
1836 
1837 	gsm_control_reply(gsm, CMD_RLS, data, clen);
1838 }
1839 
1840 static void gsm_dlci_begin_close(struct gsm_dlci *dlci);
1841 
1842 /**
1843  *	gsm_control_message	-	DLCI 0 control processing
1844  *	@gsm: our GSM mux
1845  *	@command:  the command EA
1846  *	@data: data beyond the command/length EAs
1847  *	@clen: length
1848  *
1849  *	Input processor for control messages from the other end of the link.
1850  *	Processes the incoming request and queues a response frame or an
1851  *	NSC response if not supported
1852  */
1853 
gsm_control_message(struct gsm_mux * gsm,unsigned int command,const u8 * data,int clen)1854 static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
1855 						const u8 *data, int clen)
1856 {
1857 	u8 buf[1];
1858 
1859 	switch (command) {
1860 	case CMD_CLD: {
1861 		struct gsm_dlci *dlci = gsm->dlci[0];
1862 		/* Modem wishes to close down */
1863 		if (dlci) {
1864 			dlci->dead = true;
1865 			gsm->dead = true;
1866 			gsm_dlci_begin_close(dlci);
1867 		}
1868 		}
1869 		break;
1870 	case CMD_TEST:
1871 		/* Modem wishes to test, reply with the data */
1872 		gsm_control_reply(gsm, CMD_TEST, data, clen);
1873 		break;
1874 	case CMD_FCON:
1875 		/* Modem can accept data again */
1876 		gsm->constipated = false;
1877 		gsm_control_reply(gsm, CMD_FCON, NULL, 0);
1878 		/* Kick the link in case it is idling */
1879 		gsmld_write_trigger(gsm);
1880 		break;
1881 	case CMD_FCOFF:
1882 		/* Modem wants us to STFU */
1883 		gsm->constipated = true;
1884 		gsm_control_reply(gsm, CMD_FCOFF, NULL, 0);
1885 		break;
1886 	case CMD_MSC:
1887 		/* Out of band modem line change indicator for a DLCI */
1888 		gsm_control_modem(gsm, data, clen);
1889 		break;
1890 	case CMD_RLS:
1891 		/* Out of band error reception for a DLCI */
1892 		gsm_control_rls(gsm, data, clen);
1893 		break;
1894 	case CMD_PSC:
1895 		/* Modem wishes to enter power saving state */
1896 		gsm_control_reply(gsm, CMD_PSC, NULL, 0);
1897 		break;
1898 		/* Optional commands */
1899 	case CMD_PN:
1900 		/* Modem sends a parameter negotiation command */
1901 		gsm_control_negotiation(gsm, 1, data, clen);
1902 		break;
1903 		/* Optional unsupported commands */
1904 	case CMD_RPN:	/* Remote port negotiation */
1905 	case CMD_SNC:	/* Service negotiation command */
1906 		gsm->unsupported++;
1907 		fallthrough;
1908 	default:
1909 		/* Reply to bad commands with an NSC */
1910 		buf[0] = command;
1911 		gsm_control_reply(gsm, CMD_NSC, buf, 1);
1912 		break;
1913 	}
1914 }
1915 
1916 /**
1917  *	gsm_control_response	-	process a response to our control
1918  *	@gsm: our GSM mux
1919  *	@command: the command (response) EA
1920  *	@data: data beyond the command/length EA
1921  *	@clen: length
1922  *
1923  *	Process a response to an outstanding command. We only allow a single
1924  *	control message in flight so this is fairly easy. All the clean up
1925  *	is done by the caller, we just update the fields, flag it as done
1926  *	and return
1927  */
1928 
gsm_control_response(struct gsm_mux * gsm,unsigned int command,const u8 * data,int clen)1929 static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
1930 						const u8 *data, int clen)
1931 {
1932 	struct gsm_control *ctrl;
1933 	struct gsm_dlci *dlci;
1934 	unsigned long flags;
1935 
1936 	spin_lock_irqsave(&gsm->control_lock, flags);
1937 
1938 	ctrl = gsm->pending_cmd;
1939 	dlci = gsm->dlci[0];
1940 	command |= 1;
1941 	/* Does the reply match our command */
1942 	if (ctrl != NULL && (command == ctrl->cmd || command == CMD_NSC)) {
1943 		/* Our command was replied to, kill the retry timer */
1944 		del_timer(&gsm->t2_timer);
1945 		gsm->pending_cmd = NULL;
1946 		/* Rejected by the other end */
1947 		if (command == CMD_NSC)
1948 			ctrl->error = -EOPNOTSUPP;
1949 		ctrl->done = 1;
1950 		wake_up(&gsm->event);
1951 	/* Or did we receive the PN response to our PN command */
1952 	} else if (command == CMD_PN) {
1953 		gsm_control_negotiation(gsm, 0, data, clen);
1954 	/* Or did we receive the TEST response to our TEST command */
1955 	} else if (command == CMD_TEST && clen == 1 && *data == gsm->ka_num) {
1956 		gsm->ka_retries = -1; /* trigger new keep-alive message */
1957 		if (dlci && !dlci->dead)
1958 			mod_timer(&gsm->ka_timer, jiffies + gsm->keep_alive * HZ / 100);
1959 	}
1960 	spin_unlock_irqrestore(&gsm->control_lock, flags);
1961 }
1962 
1963 /**
1964  * gsm_control_keep_alive	-	check timeout or start keep-alive
1965  * @t: timer contained in our gsm object
1966  *
1967  * Called off the keep-alive timer expiry signaling that our link
1968  * partner is not responding anymore. Link will be closed.
1969  * This is also called to startup our timer.
1970  */
1971 
gsm_control_keep_alive(struct timer_list * t)1972 static void gsm_control_keep_alive(struct timer_list *t)
1973 {
1974 	struct gsm_mux *gsm = from_timer(gsm, t, ka_timer);
1975 	unsigned long flags;
1976 
1977 	spin_lock_irqsave(&gsm->control_lock, flags);
1978 	if (gsm->ka_num && gsm->ka_retries == 0) {
1979 		/* Keep-alive expired -> close the link */
1980 		if (debug & DBG_ERRORS)
1981 			pr_debug("%s keep-alive timed out\n", __func__);
1982 		spin_unlock_irqrestore(&gsm->control_lock, flags);
1983 		if (gsm->dlci[0])
1984 			gsm_dlci_begin_close(gsm->dlci[0]);
1985 		return;
1986 	} else if (gsm->keep_alive && gsm->dlci[0] && !gsm->dlci[0]->dead) {
1987 		if (gsm->ka_retries > 0) {
1988 			/* T2 expired for keep-alive -> resend */
1989 			gsm->ka_retries--;
1990 		} else {
1991 			/* Start keep-alive timer */
1992 			gsm->ka_num++;
1993 			if (!gsm->ka_num)
1994 				gsm->ka_num++;
1995 			gsm->ka_retries = (signed int)gsm->n2;
1996 		}
1997 		gsm_control_command(gsm, CMD_TEST, &gsm->ka_num,
1998 				    sizeof(gsm->ka_num));
1999 		mod_timer(&gsm->ka_timer,
2000 			  jiffies + gsm->t2 * HZ / 100);
2001 	}
2002 	spin_unlock_irqrestore(&gsm->control_lock, flags);
2003 }
2004 
2005 /**
2006  *	gsm_control_transmit	-	send control packet
2007  *	@gsm: gsm mux
2008  *	@ctrl: frame to send
2009  *
2010  *	Send out a pending control command (called under control lock)
2011  */
2012 
gsm_control_transmit(struct gsm_mux * gsm,struct gsm_control * ctrl)2013 static void gsm_control_transmit(struct gsm_mux *gsm, struct gsm_control *ctrl)
2014 {
2015 	gsm_control_command(gsm, ctrl->cmd, ctrl->data, ctrl->len);
2016 }
2017 
2018 /**
2019  *	gsm_control_retransmit	-	retransmit a control frame
2020  *	@t: timer contained in our gsm object
2021  *
2022  *	Called off the T2 timer expiry in order to retransmit control frames
2023  *	that have been lost in the system somewhere. The control_lock protects
2024  *	us from colliding with another sender or a receive completion event.
2025  *	In that situation the timer may still occur in a small window but
2026  *	gsm->pending_cmd will be NULL and we just let the timer expire.
2027  */
2028 
gsm_control_retransmit(struct timer_list * t)2029 static void gsm_control_retransmit(struct timer_list *t)
2030 {
2031 	struct gsm_mux *gsm = from_timer(gsm, t, t2_timer);
2032 	struct gsm_control *ctrl;
2033 	unsigned long flags;
2034 	spin_lock_irqsave(&gsm->control_lock, flags);
2035 	ctrl = gsm->pending_cmd;
2036 	if (ctrl) {
2037 		if (gsm->cretries == 0 || !gsm->dlci[0] || gsm->dlci[0]->dead) {
2038 			gsm->pending_cmd = NULL;
2039 			ctrl->error = -ETIMEDOUT;
2040 			ctrl->done = 1;
2041 			spin_unlock_irqrestore(&gsm->control_lock, flags);
2042 			wake_up(&gsm->event);
2043 			return;
2044 		}
2045 		gsm->cretries--;
2046 		gsm_control_transmit(gsm, ctrl);
2047 		mod_timer(&gsm->t2_timer, jiffies + gsm->t2 * HZ / 100);
2048 	}
2049 	spin_unlock_irqrestore(&gsm->control_lock, flags);
2050 }
2051 
2052 /**
2053  *	gsm_control_send	-	send a control frame on DLCI 0
2054  *	@gsm: the GSM channel
2055  *	@command: command  to send including CR bit
2056  *	@data: bytes of data (must be kmalloced)
2057  *	@clen: length of the block to send
2058  *
2059  *	Queue and dispatch a control command. Only one command can be
2060  *	active at a time. In theory more can be outstanding but the matching
2061  *	gets really complicated so for now stick to one outstanding.
2062  */
2063 
gsm_control_send(struct gsm_mux * gsm,unsigned int command,u8 * data,int clen)2064 static struct gsm_control *gsm_control_send(struct gsm_mux *gsm,
2065 		unsigned int command, u8 *data, int clen)
2066 {
2067 	struct gsm_control *ctrl = kzalloc(sizeof(struct gsm_control),
2068 						GFP_ATOMIC);
2069 	unsigned long flags;
2070 	if (ctrl == NULL)
2071 		return NULL;
2072 retry:
2073 	wait_event(gsm->event, gsm->pending_cmd == NULL);
2074 	spin_lock_irqsave(&gsm->control_lock, flags);
2075 	if (gsm->pending_cmd != NULL) {
2076 		spin_unlock_irqrestore(&gsm->control_lock, flags);
2077 		goto retry;
2078 	}
2079 	ctrl->cmd = command;
2080 	ctrl->data = data;
2081 	ctrl->len = clen;
2082 	gsm->pending_cmd = ctrl;
2083 
2084 	/* If DLCI0 is in ADM mode skip retries, it won't respond */
2085 	if (gsm->dlci[0]->mode == DLCI_MODE_ADM)
2086 		gsm->cretries = 0;
2087 	else
2088 		gsm->cretries = gsm->n2;
2089 
2090 	mod_timer(&gsm->t2_timer, jiffies + gsm->t2 * HZ / 100);
2091 	gsm_control_transmit(gsm, ctrl);
2092 	spin_unlock_irqrestore(&gsm->control_lock, flags);
2093 	return ctrl;
2094 }
2095 
2096 /**
2097  *	gsm_control_wait	-	wait for a control to finish
2098  *	@gsm: GSM mux
2099  *	@control: control we are waiting on
2100  *
2101  *	Waits for the control to complete or time out. Frees any used
2102  *	resources and returns 0 for success, or an error if the remote
2103  *	rejected or ignored the request.
2104  */
2105 
gsm_control_wait(struct gsm_mux * gsm,struct gsm_control * control)2106 static int gsm_control_wait(struct gsm_mux *gsm, struct gsm_control *control)
2107 {
2108 	int err;
2109 	wait_event(gsm->event, control->done == 1);
2110 	err = control->error;
2111 	kfree(control);
2112 	return err;
2113 }
2114 
2115 
2116 /*
2117  *	DLCI level handling: Needs krefs
2118  */
2119 
2120 /*
2121  *	State transitions and timers
2122  */
2123 
2124 /**
2125  *	gsm_dlci_close		-	a DLCI has closed
2126  *	@dlci: DLCI that closed
2127  *
2128  *	Perform processing when moving a DLCI into closed state. If there
2129  *	is an attached tty this is hung up
2130  */
2131 
gsm_dlci_close(struct gsm_dlci * dlci)2132 static void gsm_dlci_close(struct gsm_dlci *dlci)
2133 {
2134 	del_timer(&dlci->t1);
2135 	if (debug & DBG_ERRORS)
2136 		pr_debug("DLCI %d goes closed.\n", dlci->addr);
2137 	dlci->state = DLCI_CLOSED;
2138 	/* Prevent us from sending data before the link is up again */
2139 	dlci->constipated = true;
2140 	if (dlci->addr != 0) {
2141 		tty_port_tty_hangup(&dlci->port, false);
2142 		gsm_dlci_clear_queues(dlci->gsm, dlci);
2143 		/* Ensure that gsmtty_open() can return. */
2144 		tty_port_set_initialized(&dlci->port, false);
2145 		wake_up_interruptible(&dlci->port.open_wait);
2146 	} else {
2147 		del_timer(&dlci->gsm->ka_timer);
2148 		dlci->gsm->dead = true;
2149 	}
2150 	/* A DLCI 0 close is a MUX termination so we need to kick that
2151 	   back to userspace somehow */
2152 	gsm_dlci_data_kick(dlci);
2153 	wake_up_all(&dlci->gsm->event);
2154 }
2155 
2156 /**
2157  *	gsm_dlci_open		-	a DLCI has opened
2158  *	@dlci: DLCI that opened
2159  *
2160  *	Perform processing when moving a DLCI into open state.
2161  */
2162 
gsm_dlci_open(struct gsm_dlci * dlci)2163 static void gsm_dlci_open(struct gsm_dlci *dlci)
2164 {
2165 	struct gsm_mux *gsm = dlci->gsm;
2166 
2167 	/* Note that SABM UA .. SABM UA first UA lost can mean that we go
2168 	   open -> open */
2169 	del_timer(&dlci->t1);
2170 	/* This will let a tty open continue */
2171 	dlci->state = DLCI_OPEN;
2172 	dlci->constipated = false;
2173 	if (debug & DBG_ERRORS)
2174 		pr_debug("DLCI %d goes open.\n", dlci->addr);
2175 	/* Send current modem state */
2176 	if (dlci->addr) {
2177 		gsm_modem_update(dlci, 0);
2178 	} else {
2179 		/* Start keep-alive control */
2180 		gsm->ka_num = 0;
2181 		gsm->ka_retries = -1;
2182 		mod_timer(&gsm->ka_timer,
2183 			  jiffies + gsm->keep_alive * HZ / 100);
2184 	}
2185 	gsm_dlci_data_kick(dlci);
2186 	wake_up(&dlci->gsm->event);
2187 }
2188 
2189 /**
2190  * gsm_dlci_negotiate	-	start parameter negotiation
2191  * @dlci: DLCI to open
2192  *
2193  * Starts the parameter negotiation for the new DLCI. This needs to be done
2194  * before the DLCI initialized the channel via SABM.
2195  */
gsm_dlci_negotiate(struct gsm_dlci * dlci)2196 static int gsm_dlci_negotiate(struct gsm_dlci *dlci)
2197 {
2198 	struct gsm_mux *gsm = dlci->gsm;
2199 	struct gsm_dlci_param_bits params;
2200 	int ret;
2201 
2202 	ret = gsm_encode_params(dlci, &params);
2203 	if (ret != 0)
2204 		return ret;
2205 
2206 	/* We cannot asynchronous wait for the command response with
2207 	 * gsm_command() and gsm_control_wait() at this point.
2208 	 */
2209 	ret = gsm_control_command(gsm, CMD_PN, (const u8 *)&params,
2210 				  sizeof(params));
2211 
2212 	return ret;
2213 }
2214 
2215 /**
2216  *	gsm_dlci_t1		-	T1 timer expiry
2217  *	@t: timer contained in the DLCI that opened
2218  *
2219  *	The T1 timer handles retransmits of control frames (essentially of
2220  *	SABM and DISC). We resend the command until the retry count runs out
2221  *	in which case an opening port goes back to closed and a closing port
2222  *	is simply put into closed state (any further frames from the other
2223  *	end will get a DM response)
2224  *
2225  *	Some control dlci can stay in ADM mode with other dlci working just
2226  *	fine. In that case we can just keep the control dlci open after the
2227  *	DLCI_OPENING retries time out.
2228  */
2229 
gsm_dlci_t1(struct timer_list * t)2230 static void gsm_dlci_t1(struct timer_list *t)
2231 {
2232 	struct gsm_dlci *dlci = from_timer(dlci, t, t1);
2233 	struct gsm_mux *gsm = dlci->gsm;
2234 
2235 	switch (dlci->state) {
2236 	case DLCI_CONFIGURE:
2237 		if (dlci->retries && gsm_dlci_negotiate(dlci) == 0) {
2238 			dlci->retries--;
2239 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2240 		} else {
2241 			gsm->open_error++;
2242 			gsm_dlci_begin_close(dlci); /* prevent half open link */
2243 		}
2244 		break;
2245 	case DLCI_OPENING:
2246 		if (dlci->retries) {
2247 			dlci->retries--;
2248 			gsm_command(dlci->gsm, dlci->addr, SABM|PF);
2249 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2250 		} else if (!dlci->addr && gsm->control == (DM | PF)) {
2251 			if (debug & DBG_ERRORS)
2252 				pr_info("DLCI %d opening in ADM mode.\n",
2253 					dlci->addr);
2254 			dlci->mode = DLCI_MODE_ADM;
2255 			gsm_dlci_open(dlci);
2256 		} else {
2257 			gsm->open_error++;
2258 			gsm_dlci_begin_close(dlci); /* prevent half open link */
2259 		}
2260 
2261 		break;
2262 	case DLCI_CLOSING:
2263 		if (dlci->retries) {
2264 			dlci->retries--;
2265 			gsm_command(dlci->gsm, dlci->addr, DISC|PF);
2266 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2267 		} else
2268 			gsm_dlci_close(dlci);
2269 		break;
2270 	default:
2271 		pr_debug("%s: unhandled state: %d\n", __func__, dlci->state);
2272 		break;
2273 	}
2274 }
2275 
2276 /**
2277  *	gsm_dlci_begin_open	-	start channel open procedure
2278  *	@dlci: DLCI to open
2279  *
2280  *	Commence opening a DLCI from the Linux side. We issue SABM messages
2281  *	to the modem which should then reply with a UA or ADM, at which point
2282  *	we will move into open state. Opening is done asynchronously with retry
2283  *	running off timers and the responses.
2284  *	Parameter negotiation is performed before SABM if required.
2285  */
2286 
gsm_dlci_begin_open(struct gsm_dlci * dlci)2287 static void gsm_dlci_begin_open(struct gsm_dlci *dlci)
2288 {
2289 	struct gsm_mux *gsm = dlci ? dlci->gsm : NULL;
2290 	bool need_pn = false;
2291 
2292 	if (!gsm)
2293 		return;
2294 
2295 	if (dlci->addr != 0) {
2296 		if (gsm->adaption != 1 || gsm->adaption != dlci->adaption)
2297 			need_pn = true;
2298 		if (dlci->prio != (roundup(dlci->addr + 1, 8) - 1))
2299 			need_pn = true;
2300 		if (gsm->ftype != dlci->ftype)
2301 			need_pn = true;
2302 	}
2303 
2304 	switch (dlci->state) {
2305 	case DLCI_CLOSED:
2306 	case DLCI_WAITING_CONFIG:
2307 	case DLCI_CLOSING:
2308 		dlci->retries = gsm->n2;
2309 		if (!need_pn) {
2310 			dlci->state = DLCI_OPENING;
2311 			gsm_command(gsm, dlci->addr, SABM|PF);
2312 		} else {
2313 			/* Configure DLCI before setup */
2314 			dlci->state = DLCI_CONFIGURE;
2315 			if (gsm_dlci_negotiate(dlci) != 0) {
2316 				gsm_dlci_close(dlci);
2317 				return;
2318 			}
2319 		}
2320 		mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2321 		break;
2322 	default:
2323 		break;
2324 	}
2325 }
2326 
2327 /**
2328  *	gsm_dlci_set_opening	-	change state to opening
2329  *	@dlci: DLCI to open
2330  *
2331  *	Change internal state to wait for DLCI open from initiator side.
2332  *	We set off timers and responses upon reception of an SABM.
2333  */
gsm_dlci_set_opening(struct gsm_dlci * dlci)2334 static void gsm_dlci_set_opening(struct gsm_dlci *dlci)
2335 {
2336 	switch (dlci->state) {
2337 	case DLCI_CLOSED:
2338 	case DLCI_WAITING_CONFIG:
2339 	case DLCI_CLOSING:
2340 		dlci->state = DLCI_OPENING;
2341 		break;
2342 	default:
2343 		break;
2344 	}
2345 }
2346 
2347 /**
2348  * gsm_dlci_set_wait_config	-	wait for channel configuration
2349  * @dlci: DLCI to configure
2350  *
2351  * Wait for a DLCI configuration from the application.
2352  */
gsm_dlci_set_wait_config(struct gsm_dlci * dlci)2353 static void gsm_dlci_set_wait_config(struct gsm_dlci *dlci)
2354 {
2355 	switch (dlci->state) {
2356 	case DLCI_CLOSED:
2357 	case DLCI_CLOSING:
2358 		dlci->state = DLCI_WAITING_CONFIG;
2359 		break;
2360 	default:
2361 		break;
2362 	}
2363 }
2364 
2365 /**
2366  *	gsm_dlci_begin_close	-	start channel open procedure
2367  *	@dlci: DLCI to open
2368  *
2369  *	Commence closing a DLCI from the Linux side. We issue DISC messages
2370  *	to the modem which should then reply with a UA, at which point we
2371  *	will move into closed state. Closing is done asynchronously with retry
2372  *	off timers. We may also receive a DM reply from the other end which
2373  *	indicates the channel was already closed.
2374  */
2375 
gsm_dlci_begin_close(struct gsm_dlci * dlci)2376 static void gsm_dlci_begin_close(struct gsm_dlci *dlci)
2377 {
2378 	struct gsm_mux *gsm = dlci->gsm;
2379 	if (dlci->state == DLCI_CLOSED || dlci->state == DLCI_CLOSING)
2380 		return;
2381 	dlci->retries = gsm->n2;
2382 	dlci->state = DLCI_CLOSING;
2383 	gsm_command(dlci->gsm, dlci->addr, DISC|PF);
2384 	mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2385 	wake_up_interruptible(&gsm->event);
2386 }
2387 
2388 /**
2389  *	gsm_dlci_data		-	data arrived
2390  *	@dlci: channel
2391  *	@data: block of bytes received
2392  *	@clen: length of received block
2393  *
2394  *	A UI or UIH frame has arrived which contains data for a channel
2395  *	other than the control channel. If the relevant virtual tty is
2396  *	open we shovel the bits down it, if not we drop them.
2397  */
2398 
gsm_dlci_data(struct gsm_dlci * dlci,const u8 * data,int clen)2399 static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
2400 {
2401 	/* krefs .. */
2402 	struct tty_port *port = &dlci->port;
2403 	struct tty_struct *tty;
2404 	unsigned int modem = 0;
2405 	int len;
2406 
2407 	if (debug & DBG_TTY)
2408 		pr_debug("%d bytes for tty\n", clen);
2409 	switch (dlci->adaption)  {
2410 	/* Unsupported types */
2411 	case 4:		/* Packetised interruptible data */
2412 		break;
2413 	case 3:		/* Packetised uininterruptible voice/data */
2414 		break;
2415 	case 2:		/* Asynchronous serial with line state in each frame */
2416 		len = gsm_read_ea_val(&modem, data, clen);
2417 		if (len < 1)
2418 			return;
2419 		tty = tty_port_tty_get(port);
2420 		if (tty) {
2421 			gsm_process_modem(tty, dlci, modem, len);
2422 			tty_wakeup(tty);
2423 			tty_kref_put(tty);
2424 		}
2425 		/* Skip processed modem data */
2426 		data += len;
2427 		clen -= len;
2428 		fallthrough;
2429 	case 1:		/* Line state will go via DLCI 0 controls only */
2430 	default:
2431 		tty_insert_flip_string(port, data, clen);
2432 		tty_flip_buffer_push(port);
2433 	}
2434 }
2435 
2436 /**
2437  *	gsm_dlci_command	-	data arrived on control channel
2438  *	@dlci: channel
2439  *	@data: block of bytes received
2440  *	@len: length of received block
2441  *
2442  *	A UI or UIH frame has arrived which contains data for DLCI 0 the
2443  *	control channel. This should contain a command EA followed by
2444  *	control data bytes. The command EA contains a command/response bit
2445  *	and we divide up the work accordingly.
2446  */
2447 
gsm_dlci_command(struct gsm_dlci * dlci,const u8 * data,int len)2448 static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
2449 {
2450 	/* See what command is involved */
2451 	unsigned int command = 0;
2452 	unsigned int clen = 0;
2453 	unsigned int dlen;
2454 
2455 	/* read the command */
2456 	dlen = gsm_read_ea_val(&command, data, len);
2457 	len -= dlen;
2458 	data += dlen;
2459 
2460 	/* read any control data */
2461 	dlen = gsm_read_ea_val(&clen, data, len);
2462 	len -= dlen;
2463 	data += dlen;
2464 
2465 	/* Malformed command? */
2466 	if (clen > len) {
2467 		dlci->gsm->malformed++;
2468 		return;
2469 	}
2470 
2471 	if (command & 1)
2472 		gsm_control_message(dlci->gsm, command, data, clen);
2473 	else
2474 		gsm_control_response(dlci->gsm, command, data, clen);
2475 }
2476 
2477 /**
2478  *	gsm_kick_timer	-	transmit if possible
2479  *	@t: timer contained in our gsm object
2480  *
2481  *	Transmit data from DLCIs if the queue is empty. We can't rely on
2482  *	a tty wakeup except when we filled the pipe so we need to fire off
2483  *	new data ourselves in other cases.
2484  */
gsm_kick_timer(struct timer_list * t)2485 static void gsm_kick_timer(struct timer_list *t)
2486 {
2487 	struct gsm_mux *gsm = from_timer(gsm, t, kick_timer);
2488 	unsigned long flags;
2489 	int sent = 0;
2490 
2491 	spin_lock_irqsave(&gsm->tx_lock, flags);
2492 	/* If we have nothing running then we need to fire up */
2493 	if (gsm->tx_bytes < TX_THRESH_LO)
2494 		sent = gsm_dlci_data_sweep(gsm);
2495 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
2496 
2497 	if (sent && debug & DBG_DATA)
2498 		pr_info("%s TX queue stalled\n", __func__);
2499 }
2500 
2501 /**
2502  * gsm_dlci_copy_config_values	-	copy DLCI configuration
2503  * @dlci: source DLCI
2504  * @dc: configuration structure to fill
2505  */
gsm_dlci_copy_config_values(struct gsm_dlci * dlci,struct gsm_dlci_config * dc)2506 static void gsm_dlci_copy_config_values(struct gsm_dlci *dlci, struct gsm_dlci_config *dc)
2507 {
2508 	memset(dc, 0, sizeof(*dc));
2509 	dc->channel = (u32)dlci->addr;
2510 	dc->adaption = (u32)dlci->adaption;
2511 	dc->mtu = (u32)dlci->mtu;
2512 	dc->priority = (u32)dlci->prio;
2513 	if (dlci->ftype == UIH)
2514 		dc->i = 1;
2515 	else
2516 		dc->i = 2;
2517 	dc->k = (u32)dlci->k;
2518 }
2519 
2520 /**
2521  * gsm_dlci_config	-	configure DLCI from configuration
2522  * @dlci: DLCI to configure
2523  * @dc: DLCI configuration
2524  * @open: open DLCI after configuration?
2525  */
gsm_dlci_config(struct gsm_dlci * dlci,struct gsm_dlci_config * dc,int open)2526 static int gsm_dlci_config(struct gsm_dlci *dlci, struct gsm_dlci_config *dc, int open)
2527 {
2528 	struct gsm_mux *gsm;
2529 	bool need_restart = false;
2530 	bool need_open = false;
2531 	unsigned int i;
2532 
2533 	/*
2534 	 * Check that userspace doesn't put stuff in here to prevent breakages
2535 	 * in the future.
2536 	 */
2537 	for (i = 0; i < ARRAY_SIZE(dc->reserved); i++)
2538 		if (dc->reserved[i])
2539 			return -EINVAL;
2540 
2541 	if (!dlci)
2542 		return -EINVAL;
2543 	gsm = dlci->gsm;
2544 
2545 	/* Stuff we don't support yet - I frame transport */
2546 	if (dc->adaption != 1 && dc->adaption != 2)
2547 		return -EOPNOTSUPP;
2548 	if (dc->mtu > MAX_MTU || dc->mtu < MIN_MTU || dc->mtu > gsm->mru)
2549 		return -EINVAL;
2550 	if (dc->priority >= 64)
2551 		return -EINVAL;
2552 	if (dc->i == 0 || dc->i > 2)  /* UIH and UI only */
2553 		return -EINVAL;
2554 	if (dc->k > 7)
2555 		return -EINVAL;
2556 	if (dc->flags & ~GSM_FL_RESTART)   /* allow future extensions */
2557 		return -EINVAL;
2558 
2559 	/*
2560 	 * See what is needed for reconfiguration
2561 	 */
2562 	/* Framing fields */
2563 	if (dc->adaption != dlci->adaption)
2564 		need_restart = true;
2565 	if (dc->mtu != dlci->mtu)
2566 		need_restart = true;
2567 	if (dc->i != dlci->ftype)
2568 		need_restart = true;
2569 	/* Requires care */
2570 	if (dc->priority != dlci->prio)
2571 		need_restart = true;
2572 	if (dc->flags & GSM_FL_RESTART)
2573 		need_restart = true;
2574 
2575 	if ((open && gsm->wait_config) || need_restart)
2576 		need_open = true;
2577 	if (dlci->state == DLCI_WAITING_CONFIG) {
2578 		need_restart = false;
2579 		need_open = true;
2580 	}
2581 
2582 	/*
2583 	 * Close down what is needed, restart and initiate the new
2584 	 * configuration.
2585 	 */
2586 	if (need_restart) {
2587 		gsm_dlci_begin_close(dlci);
2588 		wait_event_interruptible(gsm->event, dlci->state == DLCI_CLOSED);
2589 		if (signal_pending(current))
2590 			return -EINTR;
2591 	}
2592 	/*
2593 	 * Setup the new configuration values
2594 	 */
2595 	dlci->adaption = (int)dc->adaption;
2596 
2597 	if (dc->mtu)
2598 		dlci->mtu = (unsigned int)dc->mtu;
2599 	else
2600 		dlci->mtu = gsm->mtu;
2601 
2602 	if (dc->priority)
2603 		dlci->prio = (u8)dc->priority;
2604 	else
2605 		dlci->prio = roundup(dlci->addr + 1, 8) - 1;
2606 
2607 	if (dc->i == 1)
2608 		dlci->ftype = UIH;
2609 	else if (dc->i == 2)
2610 		dlci->ftype = UI;
2611 
2612 	if (dc->k)
2613 		dlci->k = (u8)dc->k;
2614 	else
2615 		dlci->k = gsm->k;
2616 
2617 	if (need_open) {
2618 		if (gsm->initiator)
2619 			gsm_dlci_begin_open(dlci);
2620 		else
2621 			gsm_dlci_set_opening(dlci);
2622 	}
2623 
2624 	return 0;
2625 }
2626 
2627 /*
2628  *	Allocate/Free DLCI channels
2629  */
2630 
2631 /**
2632  *	gsm_dlci_alloc		-	allocate a DLCI
2633  *	@gsm: GSM mux
2634  *	@addr: address of the DLCI
2635  *
2636  *	Allocate and install a new DLCI object into the GSM mux.
2637  *
2638  *	FIXME: review locking races
2639  */
2640 
gsm_dlci_alloc(struct gsm_mux * gsm,int addr)2641 static struct gsm_dlci *gsm_dlci_alloc(struct gsm_mux *gsm, int addr)
2642 {
2643 	struct gsm_dlci *dlci = kzalloc(sizeof(struct gsm_dlci), GFP_ATOMIC);
2644 	if (dlci == NULL)
2645 		return NULL;
2646 	spin_lock_init(&dlci->lock);
2647 	mutex_init(&dlci->mutex);
2648 	if (kfifo_alloc(&dlci->fifo, TX_SIZE, GFP_KERNEL) < 0) {
2649 		kfree(dlci);
2650 		return NULL;
2651 	}
2652 
2653 	skb_queue_head_init(&dlci->skb_list);
2654 	timer_setup(&dlci->t1, gsm_dlci_t1, 0);
2655 	tty_port_init(&dlci->port);
2656 	dlci->port.ops = &gsm_port_ops;
2657 	dlci->gsm = gsm;
2658 	dlci->addr = addr;
2659 	dlci->adaption = gsm->adaption;
2660 	dlci->mtu = gsm->mtu;
2661 	if (addr == 0)
2662 		dlci->prio = 0;
2663 	else
2664 		dlci->prio = roundup(addr + 1, 8) - 1;
2665 	dlci->ftype = gsm->ftype;
2666 	dlci->k = gsm->k;
2667 	dlci->state = DLCI_CLOSED;
2668 	if (addr) {
2669 		dlci->data = gsm_dlci_data;
2670 		/* Prevent us from sending data before the link is up */
2671 		dlci->constipated = true;
2672 	} else {
2673 		dlci->data = gsm_dlci_command;
2674 	}
2675 	gsm->dlci[addr] = dlci;
2676 	return dlci;
2677 }
2678 
2679 /**
2680  *	gsm_dlci_free		-	free DLCI
2681  *	@port: tty port for DLCI to free
2682  *
2683  *	Free up a DLCI.
2684  *
2685  *	Can sleep.
2686  */
gsm_dlci_free(struct tty_port * port)2687 static void gsm_dlci_free(struct tty_port *port)
2688 {
2689 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
2690 
2691 	timer_shutdown_sync(&dlci->t1);
2692 	dlci->gsm->dlci[dlci->addr] = NULL;
2693 	kfifo_free(&dlci->fifo);
2694 	while ((dlci->skb = skb_dequeue(&dlci->skb_list)))
2695 		dev_kfree_skb(dlci->skb);
2696 	kfree(dlci);
2697 }
2698 
dlci_get(struct gsm_dlci * dlci)2699 static inline void dlci_get(struct gsm_dlci *dlci)
2700 {
2701 	tty_port_get(&dlci->port);
2702 }
2703 
dlci_put(struct gsm_dlci * dlci)2704 static inline void dlci_put(struct gsm_dlci *dlci)
2705 {
2706 	tty_port_put(&dlci->port);
2707 }
2708 
2709 static void gsm_destroy_network(struct gsm_dlci *dlci);
2710 
2711 /**
2712  *	gsm_dlci_release		-	release DLCI
2713  *	@dlci: DLCI to destroy
2714  *
2715  *	Release a DLCI. Actual free is deferred until either
2716  *	mux is closed or tty is closed - whichever is last.
2717  *
2718  *	Can sleep.
2719  */
gsm_dlci_release(struct gsm_dlci * dlci)2720 static void gsm_dlci_release(struct gsm_dlci *dlci)
2721 {
2722 	struct tty_struct *tty = tty_port_tty_get(&dlci->port);
2723 	if (tty) {
2724 		mutex_lock(&dlci->mutex);
2725 		gsm_destroy_network(dlci);
2726 		mutex_unlock(&dlci->mutex);
2727 
2728 		/* We cannot use tty_hangup() because in tty_kref_put() the tty
2729 		 * driver assumes that the hangup queue is free and reuses it to
2730 		 * queue release_one_tty() -> NULL pointer panic in
2731 		 * process_one_work().
2732 		 */
2733 		tty_vhangup(tty);
2734 
2735 		tty_port_tty_set(&dlci->port, NULL);
2736 		tty_kref_put(tty);
2737 	}
2738 	dlci->state = DLCI_CLOSED;
2739 	dlci_put(dlci);
2740 }
2741 
2742 /*
2743  *	LAPBish link layer logic
2744  */
2745 
2746 /**
2747  *	gsm_queue		-	a GSM frame is ready to process
2748  *	@gsm: pointer to our gsm mux
2749  *
2750  *	At this point in time a frame has arrived and been demangled from
2751  *	the line encoding. All the differences between the encodings have
2752  *	been handled below us and the frame is unpacked into the structures.
2753  *	The fcs holds the header FCS but any data FCS must be added here.
2754  */
2755 
gsm_queue(struct gsm_mux * gsm)2756 static void gsm_queue(struct gsm_mux *gsm)
2757 {
2758 	struct gsm_dlci *dlci;
2759 	u8 cr;
2760 	int address;
2761 
2762 	if (gsm->fcs != GOOD_FCS) {
2763 		gsm->bad_fcs++;
2764 		if (debug & DBG_DATA)
2765 			pr_debug("BAD FCS %02x\n", gsm->fcs);
2766 		return;
2767 	}
2768 	address = gsm->address >> 1;
2769 	if (address >= NUM_DLCI)
2770 		goto invalid;
2771 
2772 	cr = gsm->address & 1;		/* C/R bit */
2773 	cr ^= gsm->initiator ? 0 : 1;	/* Flip so 1 always means command */
2774 
2775 	gsm_print_packet("<--", address, cr, gsm->control, gsm->buf, gsm->len);
2776 
2777 	dlci = gsm->dlci[address];
2778 
2779 	switch (gsm->control) {
2780 	case SABM|PF:
2781 		if (cr == 1) {
2782 			gsm->open_error++;
2783 			goto invalid;
2784 		}
2785 		if (dlci == NULL)
2786 			dlci = gsm_dlci_alloc(gsm, address);
2787 		if (dlci == NULL) {
2788 			gsm->open_error++;
2789 			return;
2790 		}
2791 		if (dlci->dead)
2792 			gsm_response(gsm, address, DM|PF);
2793 		else {
2794 			gsm_response(gsm, address, UA|PF);
2795 			gsm_dlci_open(dlci);
2796 		}
2797 		break;
2798 	case DISC|PF:
2799 		if (cr == 1)
2800 			goto invalid;
2801 		if (dlci == NULL || dlci->state == DLCI_CLOSED) {
2802 			gsm_response(gsm, address, DM|PF);
2803 			return;
2804 		}
2805 		/* Real close complete */
2806 		gsm_response(gsm, address, UA|PF);
2807 		gsm_dlci_close(dlci);
2808 		break;
2809 	case UA|PF:
2810 		if (cr == 0 || dlci == NULL)
2811 			break;
2812 		switch (dlci->state) {
2813 		case DLCI_CLOSING:
2814 			gsm_dlci_close(dlci);
2815 			break;
2816 		case DLCI_OPENING:
2817 			gsm_dlci_open(dlci);
2818 			break;
2819 		default:
2820 			pr_debug("%s: unhandled state: %d\n", __func__,
2821 					dlci->state);
2822 			break;
2823 		}
2824 		break;
2825 	case DM:	/* DM can be valid unsolicited */
2826 	case DM|PF:
2827 		if (cr)
2828 			goto invalid;
2829 		if (dlci == NULL)
2830 			return;
2831 		gsm_dlci_close(dlci);
2832 		break;
2833 	case UI:
2834 	case UI|PF:
2835 	case UIH:
2836 	case UIH|PF:
2837 		if (dlci == NULL || dlci->state != DLCI_OPEN) {
2838 			gsm_response(gsm, address, DM|PF);
2839 			return;
2840 		}
2841 		dlci->data(dlci, gsm->buf, gsm->len);
2842 		break;
2843 	default:
2844 		goto invalid;
2845 	}
2846 	return;
2847 invalid:
2848 	gsm->malformed++;
2849 	return;
2850 }
2851 
2852 /**
2853  * gsm0_receive_state_check_and_fix	-	check and correct receive state
2854  * @gsm: gsm data for this ldisc instance
2855  *
2856  * Ensures that the current receive state is valid for basic option mode.
2857  */
2858 
gsm0_receive_state_check_and_fix(struct gsm_mux * gsm)2859 static void gsm0_receive_state_check_and_fix(struct gsm_mux *gsm)
2860 {
2861 	switch (gsm->state) {
2862 	case GSM_SEARCH:
2863 	case GSM0_ADDRESS:
2864 	case GSM0_CONTROL:
2865 	case GSM0_LEN0:
2866 	case GSM0_LEN1:
2867 	case GSM0_DATA:
2868 	case GSM0_FCS:
2869 	case GSM0_SSOF:
2870 		break;
2871 	default:
2872 		gsm->state = GSM_SEARCH;
2873 		break;
2874 	}
2875 }
2876 
2877 /**
2878  *	gsm0_receive	-	perform processing for non-transparency
2879  *	@gsm: gsm data for this ldisc instance
2880  *	@c: character
2881  *
2882  *	Receive bytes in gsm mode 0
2883  */
2884 
gsm0_receive(struct gsm_mux * gsm,u8 c)2885 static void gsm0_receive(struct gsm_mux *gsm, u8 c)
2886 {
2887 	unsigned int len;
2888 
2889 	gsm0_receive_state_check_and_fix(gsm);
2890 	switch (gsm->state) {
2891 	case GSM_SEARCH:	/* SOF marker */
2892 		if (c == GSM0_SOF) {
2893 			gsm->state = GSM0_ADDRESS;
2894 			gsm->address = 0;
2895 			gsm->len = 0;
2896 			gsm->fcs = INIT_FCS;
2897 		}
2898 		break;
2899 	case GSM0_ADDRESS:	/* Address EA */
2900 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2901 		if (gsm_read_ea(&gsm->address, c))
2902 			gsm->state = GSM0_CONTROL;
2903 		break;
2904 	case GSM0_CONTROL:	/* Control Byte */
2905 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2906 		gsm->control = c;
2907 		gsm->state = GSM0_LEN0;
2908 		break;
2909 	case GSM0_LEN0:		/* Length EA */
2910 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2911 		if (gsm_read_ea(&gsm->len, c)) {
2912 			if (gsm->len > gsm->mru) {
2913 				gsm->bad_size++;
2914 				gsm->state = GSM_SEARCH;
2915 				break;
2916 			}
2917 			gsm->count = 0;
2918 			if (!gsm->len)
2919 				gsm->state = GSM0_FCS;
2920 			else
2921 				gsm->state = GSM0_DATA;
2922 			break;
2923 		}
2924 		gsm->state = GSM0_LEN1;
2925 		break;
2926 	case GSM0_LEN1:
2927 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2928 		len = c;
2929 		gsm->len |= len << 7;
2930 		if (gsm->len > gsm->mru) {
2931 			gsm->bad_size++;
2932 			gsm->state = GSM_SEARCH;
2933 			break;
2934 		}
2935 		gsm->count = 0;
2936 		if (!gsm->len)
2937 			gsm->state = GSM0_FCS;
2938 		else
2939 			gsm->state = GSM0_DATA;
2940 		break;
2941 	case GSM0_DATA:		/* Data */
2942 		gsm->buf[gsm->count++] = c;
2943 		if (gsm->count >= MAX_MRU) {
2944 			gsm->bad_size++;
2945 			gsm->state = GSM_SEARCH;
2946 		} else if (gsm->count >= gsm->len) {
2947 			/* Calculate final FCS for UI frames over all data */
2948 			if ((gsm->control & ~PF) != UIH) {
2949 				gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf,
2950 							     gsm->count);
2951 			}
2952 			gsm->state = GSM0_FCS;
2953 		}
2954 		break;
2955 	case GSM0_FCS:		/* FCS follows the packet */
2956 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2957 		gsm->state = GSM0_SSOF;
2958 		break;
2959 	case GSM0_SSOF:
2960 		gsm->state = GSM_SEARCH;
2961 		if (c == GSM0_SOF)
2962 			gsm_queue(gsm);
2963 		else
2964 			gsm->bad_size++;
2965 		break;
2966 	default:
2967 		pr_debug("%s: unhandled state: %d\n", __func__, gsm->state);
2968 		break;
2969 	}
2970 }
2971 
2972 /**
2973  * gsm1_receive_state_check_and_fix	-	check and correct receive state
2974  * @gsm: gsm data for this ldisc instance
2975  *
2976  * Ensures that the current receive state is valid for advanced option mode.
2977  */
2978 
gsm1_receive_state_check_and_fix(struct gsm_mux * gsm)2979 static void gsm1_receive_state_check_and_fix(struct gsm_mux *gsm)
2980 {
2981 	switch (gsm->state) {
2982 	case GSM_SEARCH:
2983 	case GSM1_START:
2984 	case GSM1_ADDRESS:
2985 	case GSM1_CONTROL:
2986 	case GSM1_DATA:
2987 	case GSM1_OVERRUN:
2988 		break;
2989 	default:
2990 		gsm->state = GSM_SEARCH;
2991 		break;
2992 	}
2993 }
2994 
2995 /**
2996  *	gsm1_receive	-	perform processing for non-transparency
2997  *	@gsm: gsm data for this ldisc instance
2998  *	@c: character
2999  *
3000  *	Receive bytes in mode 1 (Advanced option)
3001  */
3002 
gsm1_receive(struct gsm_mux * gsm,u8 c)3003 static void gsm1_receive(struct gsm_mux *gsm, u8 c)
3004 {
3005 	gsm1_receive_state_check_and_fix(gsm);
3006 	/* handle XON/XOFF */
3007 	if ((c & ISO_IEC_646_MASK) == XON) {
3008 		gsm->constipated = true;
3009 		return;
3010 	} else if ((c & ISO_IEC_646_MASK) == XOFF) {
3011 		gsm->constipated = false;
3012 		/* Kick the link in case it is idling */
3013 		gsmld_write_trigger(gsm);
3014 		return;
3015 	}
3016 	if (c == GSM1_SOF) {
3017 		/* EOF is only valid in frame if we have got to the data state */
3018 		if (gsm->state == GSM1_DATA) {
3019 			if (gsm->count < 1) {
3020 				/* Missing FSC */
3021 				gsm->malformed++;
3022 				gsm->state = GSM1_START;
3023 				return;
3024 			}
3025 			/* Remove the FCS from data */
3026 			gsm->count--;
3027 			if ((gsm->control & ~PF) != UIH) {
3028 				/* Calculate final FCS for UI frames over all
3029 				 * data but FCS
3030 				 */
3031 				gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf,
3032 							     gsm->count);
3033 			}
3034 			/* Add the FCS itself to test against GOOD_FCS */
3035 			gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->buf[gsm->count]);
3036 			gsm->len = gsm->count;
3037 			gsm_queue(gsm);
3038 			gsm->state  = GSM1_START;
3039 			return;
3040 		}
3041 		/* Any partial frame was a runt so go back to start */
3042 		if (gsm->state != GSM1_START) {
3043 			if (gsm->state != GSM_SEARCH)
3044 				gsm->malformed++;
3045 			gsm->state = GSM1_START;
3046 		}
3047 		/* A SOF in GSM_START means we are still reading idling or
3048 		   framing bytes */
3049 		return;
3050 	}
3051 
3052 	if (c == GSM1_ESCAPE) {
3053 		gsm->escape = true;
3054 		return;
3055 	}
3056 
3057 	/* Only an unescaped SOF gets us out of GSM search */
3058 	if (gsm->state == GSM_SEARCH)
3059 		return;
3060 
3061 	if (gsm->escape) {
3062 		c ^= GSM1_ESCAPE_BITS;
3063 		gsm->escape = false;
3064 	}
3065 	switch (gsm->state) {
3066 	case GSM1_START:		/* First byte after SOF */
3067 		gsm->address = 0;
3068 		gsm->state = GSM1_ADDRESS;
3069 		gsm->fcs = INIT_FCS;
3070 		fallthrough;
3071 	case GSM1_ADDRESS:	/* Address continuation */
3072 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
3073 		if (gsm_read_ea(&gsm->address, c))
3074 			gsm->state = GSM1_CONTROL;
3075 		break;
3076 	case GSM1_CONTROL:	/* Control Byte */
3077 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
3078 		gsm->control = c;
3079 		gsm->count = 0;
3080 		gsm->state = GSM1_DATA;
3081 		break;
3082 	case GSM1_DATA:		/* Data */
3083 		if (gsm->count > gsm->mru || gsm->count > MAX_MRU) {	/* Allow one for the FCS */
3084 			gsm->state = GSM1_OVERRUN;
3085 			gsm->bad_size++;
3086 		} else
3087 			gsm->buf[gsm->count++] = c;
3088 		break;
3089 	case GSM1_OVERRUN:	/* Over-long - eg a dropped SOF */
3090 		break;
3091 	default:
3092 		pr_debug("%s: unhandled state: %d\n", __func__, gsm->state);
3093 		break;
3094 	}
3095 }
3096 
3097 /**
3098  *	gsm_error		-	handle tty error
3099  *	@gsm: ldisc data
3100  *
3101  *	Handle an error in the receipt of data for a frame. Currently we just
3102  *	go back to hunting for a SOF.
3103  *
3104  *	FIXME: better diagnostics ?
3105  */
3106 
gsm_error(struct gsm_mux * gsm)3107 static void gsm_error(struct gsm_mux *gsm)
3108 {
3109 	gsm->state = GSM_SEARCH;
3110 	gsm->io_error++;
3111 }
3112 
3113 /**
3114  *	gsm_cleanup_mux		-	generic GSM protocol cleanup
3115  *	@gsm: our mux
3116  *	@disc: disconnect link?
3117  *
3118  *	Clean up the bits of the mux which are the same for all framing
3119  *	protocols. Remove the mux from the mux table, stop all the timers
3120  *	and then shut down each device hanging up the channels as we go.
3121  */
3122 
gsm_cleanup_mux(struct gsm_mux * gsm,bool disc)3123 static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
3124 {
3125 	int i;
3126 	struct gsm_dlci *dlci;
3127 	struct gsm_msg *txq, *ntxq;
3128 
3129 	gsm->dead = true;
3130 	mutex_lock(&gsm->mutex);
3131 
3132 	dlci = gsm->dlci[0];
3133 	if (dlci) {
3134 		if (disc && dlci->state != DLCI_CLOSED) {
3135 			gsm_dlci_begin_close(dlci);
3136 			wait_event(gsm->event, dlci->state == DLCI_CLOSED);
3137 		}
3138 		dlci->dead = true;
3139 	}
3140 
3141 	/* Finish outstanding timers, making sure they are done */
3142 	del_timer_sync(&gsm->kick_timer);
3143 	del_timer_sync(&gsm->t2_timer);
3144 	del_timer_sync(&gsm->ka_timer);
3145 
3146 	/* Finish writing to ldisc */
3147 	flush_work(&gsm->tx_work);
3148 
3149 	/* Free up any link layer users and finally the control channel */
3150 	if (gsm->has_devices) {
3151 		gsm_unregister_devices(gsm_tty_driver, gsm->num);
3152 		gsm->has_devices = false;
3153 	}
3154 	for (i = NUM_DLCI - 1; i >= 0; i--)
3155 		if (gsm->dlci[i])
3156 			gsm_dlci_release(gsm->dlci[i]);
3157 	mutex_unlock(&gsm->mutex);
3158 	/* Now wipe the queues */
3159 	tty_ldisc_flush(gsm->tty);
3160 
3161 	guard(spinlock_irqsave)(&gsm->tx_lock);
3162 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_ctrl_list, list)
3163 		kfree(txq);
3164 	INIT_LIST_HEAD(&gsm->tx_ctrl_list);
3165 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_data_list, list)
3166 		kfree(txq);
3167 	INIT_LIST_HEAD(&gsm->tx_data_list);
3168 }
3169 
3170 /**
3171  *	gsm_activate_mux	-	generic GSM setup
3172  *	@gsm: our mux
3173  *
3174  *	Set up the bits of the mux which are the same for all framing
3175  *	protocols. Add the mux to the mux table so it can be opened and
3176  *	finally kick off connecting to DLCI 0 on the modem.
3177  */
3178 
gsm_activate_mux(struct gsm_mux * gsm)3179 static int gsm_activate_mux(struct gsm_mux *gsm)
3180 {
3181 	struct gsm_dlci *dlci;
3182 	int ret;
3183 
3184 	dlci = gsm_dlci_alloc(gsm, 0);
3185 	if (dlci == NULL)
3186 		return -ENOMEM;
3187 
3188 	if (gsm->encoding == GSM_BASIC_OPT)
3189 		gsm->receive = gsm0_receive;
3190 	else
3191 		gsm->receive = gsm1_receive;
3192 
3193 	ret = gsm_register_devices(gsm_tty_driver, gsm->num);
3194 	if (ret)
3195 		return ret;
3196 
3197 	gsm->has_devices = true;
3198 	gsm->dead = false;		/* Tty opens are now permissible */
3199 	return 0;
3200 }
3201 
3202 /**
3203  *	gsm_free_mux		-	free up a mux
3204  *	@gsm: mux to free
3205  *
3206  *	Dispose of allocated resources for a dead mux
3207  */
gsm_free_mux(struct gsm_mux * gsm)3208 static void gsm_free_mux(struct gsm_mux *gsm)
3209 {
3210 	int i;
3211 
3212 	for (i = 0; i < MAX_MUX; i++) {
3213 		if (gsm == gsm_mux[i]) {
3214 			gsm_mux[i] = NULL;
3215 			break;
3216 		}
3217 	}
3218 	mutex_destroy(&gsm->mutex);
3219 	kfree(gsm->txframe);
3220 	kfree(gsm->buf);
3221 	kfree(gsm);
3222 }
3223 
3224 /**
3225  *	gsm_free_muxr		-	free up a mux
3226  *	@ref: kreference to the mux to free
3227  *
3228  *	Dispose of allocated resources for a dead mux
3229  */
gsm_free_muxr(struct kref * ref)3230 static void gsm_free_muxr(struct kref *ref)
3231 {
3232 	struct gsm_mux *gsm = container_of(ref, struct gsm_mux, ref);
3233 	gsm_free_mux(gsm);
3234 }
3235 
mux_get(struct gsm_mux * gsm)3236 static inline void mux_get(struct gsm_mux *gsm)
3237 {
3238 	unsigned long flags;
3239 
3240 	spin_lock_irqsave(&gsm_mux_lock, flags);
3241 	kref_get(&gsm->ref);
3242 	spin_unlock_irqrestore(&gsm_mux_lock, flags);
3243 }
3244 
mux_put(struct gsm_mux * gsm)3245 static inline void mux_put(struct gsm_mux *gsm)
3246 {
3247 	unsigned long flags;
3248 
3249 	spin_lock_irqsave(&gsm_mux_lock, flags);
3250 	kref_put(&gsm->ref, gsm_free_muxr);
3251 	spin_unlock_irqrestore(&gsm_mux_lock, flags);
3252 }
3253 
mux_num_to_base(struct gsm_mux * gsm)3254 static inline unsigned int mux_num_to_base(struct gsm_mux *gsm)
3255 {
3256 	return gsm->num * NUM_DLCI;
3257 }
3258 
mux_line_to_num(unsigned int line)3259 static inline unsigned int mux_line_to_num(unsigned int line)
3260 {
3261 	return line / NUM_DLCI;
3262 }
3263 
3264 /**
3265  *	gsm_alloc_mux		-	allocate a mux
3266  *
3267  *	Creates a new mux ready for activation.
3268  */
3269 
gsm_alloc_mux(void)3270 static struct gsm_mux *gsm_alloc_mux(void)
3271 {
3272 	int i;
3273 	struct gsm_mux *gsm = kzalloc(sizeof(struct gsm_mux), GFP_KERNEL);
3274 	if (gsm == NULL)
3275 		return NULL;
3276 	gsm->buf = kmalloc(MAX_MRU + 1, GFP_KERNEL);
3277 	if (gsm->buf == NULL) {
3278 		kfree(gsm);
3279 		return NULL;
3280 	}
3281 	gsm->txframe = kmalloc(2 * (MAX_MTU + PROT_OVERHEAD - 1), GFP_KERNEL);
3282 	if (gsm->txframe == NULL) {
3283 		kfree(gsm->buf);
3284 		kfree(gsm);
3285 		return NULL;
3286 	}
3287 	spin_lock_init(&gsm->lock);
3288 	mutex_init(&gsm->mutex);
3289 	kref_init(&gsm->ref);
3290 	INIT_LIST_HEAD(&gsm->tx_ctrl_list);
3291 	INIT_LIST_HEAD(&gsm->tx_data_list);
3292 	timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
3293 	timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
3294 	timer_setup(&gsm->ka_timer, gsm_control_keep_alive, 0);
3295 	INIT_WORK(&gsm->tx_work, gsmld_write_task);
3296 	init_waitqueue_head(&gsm->event);
3297 	spin_lock_init(&gsm->control_lock);
3298 	spin_lock_init(&gsm->tx_lock);
3299 
3300 	gsm->t1 = T1;
3301 	gsm->t2 = T2;
3302 	gsm->t3 = T3;
3303 	gsm->n2 = N2;
3304 	gsm->k = K;
3305 	gsm->ftype = UIH;
3306 	gsm->adaption = 1;
3307 	gsm->encoding = GSM_ADV_OPT;
3308 	gsm->mru = 64;	/* Default to encoding 1 so these should be 64 */
3309 	gsm->mtu = 64;
3310 	gsm->dead = true;	/* Avoid early tty opens */
3311 	gsm->wait_config = false; /* Disabled */
3312 	gsm->keep_alive = 0;	/* Disabled */
3313 
3314 	/* Store the instance to the mux array or abort if no space is
3315 	 * available.
3316 	 */
3317 	spin_lock(&gsm_mux_lock);
3318 	for (i = 0; i < MAX_MUX; i++) {
3319 		if (!gsm_mux[i]) {
3320 			gsm_mux[i] = gsm;
3321 			gsm->num = i;
3322 			break;
3323 		}
3324 	}
3325 	spin_unlock(&gsm_mux_lock);
3326 	if (i == MAX_MUX) {
3327 		mutex_destroy(&gsm->mutex);
3328 		kfree(gsm->txframe);
3329 		kfree(gsm->buf);
3330 		kfree(gsm);
3331 		return NULL;
3332 	}
3333 
3334 	return gsm;
3335 }
3336 
gsm_copy_config_values(struct gsm_mux * gsm,struct gsm_config * c)3337 static void gsm_copy_config_values(struct gsm_mux *gsm,
3338 				   struct gsm_config *c)
3339 {
3340 	memset(c, 0, sizeof(*c));
3341 	c->adaption = gsm->adaption;
3342 	c->encapsulation = gsm->encoding;
3343 	c->initiator = gsm->initiator;
3344 	c->t1 = gsm->t1;
3345 	c->t2 = gsm->t2;
3346 	c->t3 = gsm->t3;
3347 	c->n2 = gsm->n2;
3348 	if (gsm->ftype == UIH)
3349 		c->i = 1;
3350 	else
3351 		c->i = 2;
3352 	pr_debug("Ftype %d i %d\n", gsm->ftype, c->i);
3353 	c->mru = gsm->mru;
3354 	c->mtu = gsm->mtu;
3355 	c->k = gsm->k;
3356 }
3357 
gsm_config(struct gsm_mux * gsm,struct gsm_config * c)3358 static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
3359 {
3360 	int need_close = 0;
3361 	int need_restart = 0;
3362 
3363 	/* Stuff we don't support yet - UI or I frame transport */
3364 	if (c->adaption != 1 && c->adaption != 2)
3365 		return -EOPNOTSUPP;
3366 	/* Check the MRU/MTU range looks sane */
3367 	if (c->mru < MIN_MTU || c->mtu < MIN_MTU)
3368 		return -EINVAL;
3369 	if (c->mru > MAX_MRU || c->mtu > MAX_MTU)
3370 		return -EINVAL;
3371 	if (c->t3 > MAX_T3)
3372 		return -EINVAL;
3373 	if (c->n2 > 255)
3374 		return -EINVAL;
3375 	if (c->encapsulation > 1)	/* Basic, advanced, no I */
3376 		return -EINVAL;
3377 	if (c->initiator > 1)
3378 		return -EINVAL;
3379 	if (c->k > MAX_WINDOW_SIZE)
3380 		return -EINVAL;
3381 	if (c->i == 0 || c->i > 2)	/* UIH and UI only */
3382 		return -EINVAL;
3383 	/*
3384 	 * See what is needed for reconfiguration
3385 	 */
3386 
3387 	/* Timing fields */
3388 	if (c->t1 != 0 && c->t1 != gsm->t1)
3389 		need_restart = 1;
3390 	if (c->t2 != 0 && c->t2 != gsm->t2)
3391 		need_restart = 1;
3392 	if (c->encapsulation != gsm->encoding)
3393 		need_restart = 1;
3394 	if (c->adaption != gsm->adaption)
3395 		need_restart = 1;
3396 	/* Requires care */
3397 	if (c->initiator != gsm->initiator)
3398 		need_close = 1;
3399 	if (c->mru != gsm->mru)
3400 		need_restart = 1;
3401 	if (c->mtu != gsm->mtu)
3402 		need_restart = 1;
3403 
3404 	/*
3405 	 * Close down what is needed, restart and initiate the new
3406 	 * configuration. On the first time there is no DLCI[0]
3407 	 * and closing or cleaning up is not necessary.
3408 	 */
3409 	if (need_close || need_restart)
3410 		gsm_cleanup_mux(gsm, true);
3411 
3412 	gsm->initiator = c->initiator;
3413 	gsm->mru = c->mru;
3414 	gsm->mtu = c->mtu;
3415 	gsm->encoding = c->encapsulation ? GSM_ADV_OPT : GSM_BASIC_OPT;
3416 	gsm->adaption = c->adaption;
3417 	gsm->n2 = c->n2;
3418 
3419 	if (c->i == 1)
3420 		gsm->ftype = UIH;
3421 	else if (c->i == 2)
3422 		gsm->ftype = UI;
3423 
3424 	if (c->t1)
3425 		gsm->t1 = c->t1;
3426 	if (c->t2)
3427 		gsm->t2 = c->t2;
3428 	if (c->t3)
3429 		gsm->t3 = c->t3;
3430 	if (c->k)
3431 		gsm->k = c->k;
3432 
3433 	/*
3434 	 * FIXME: We need to separate activation/deactivation from adding
3435 	 * and removing from the mux array
3436 	 */
3437 	if (gsm->dead) {
3438 		int ret = gsm_activate_mux(gsm);
3439 		if (ret)
3440 			return ret;
3441 		if (gsm->initiator)
3442 			gsm_dlci_begin_open(gsm->dlci[0]);
3443 	}
3444 	return 0;
3445 }
3446 
gsm_copy_config_ext_values(struct gsm_mux * gsm,struct gsm_config_ext * ce)3447 static void gsm_copy_config_ext_values(struct gsm_mux *gsm,
3448 				       struct gsm_config_ext *ce)
3449 {
3450 	memset(ce, 0, sizeof(*ce));
3451 	ce->wait_config = gsm->wait_config ? 1 : 0;
3452 	ce->keep_alive = gsm->keep_alive;
3453 }
3454 
gsm_config_ext(struct gsm_mux * gsm,struct gsm_config_ext * ce)3455 static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)
3456 {
3457 	bool need_restart = false;
3458 	unsigned int i;
3459 
3460 	/*
3461 	 * Check that userspace doesn't put stuff in here to prevent breakages
3462 	 * in the future.
3463 	 */
3464 	for (i = 0; i < ARRAY_SIZE(ce->reserved); i++)
3465 		if (ce->reserved[i])
3466 			return -EINVAL;
3467 	if (ce->flags & ~GSM_FL_RESTART)
3468 		return -EINVAL;
3469 
3470 	/* Requires care */
3471 	if (ce->flags & GSM_FL_RESTART)
3472 		need_restart = true;
3473 
3474 	/*
3475 	 * Close down what is needed, restart and initiate the new
3476 	 * configuration. On the first time there is no DLCI[0]
3477 	 * and closing or cleaning up is not necessary.
3478 	 */
3479 	if (need_restart)
3480 		gsm_cleanup_mux(gsm, true);
3481 
3482 	/*
3483 	 * Setup the new configuration values
3484 	 */
3485 	gsm->wait_config = ce->wait_config ? true : false;
3486 	gsm->keep_alive = ce->keep_alive;
3487 
3488 	if (gsm->dead) {
3489 		int ret = gsm_activate_mux(gsm);
3490 		if (ret)
3491 			return ret;
3492 		if (gsm->initiator)
3493 			gsm_dlci_begin_open(gsm->dlci[0]);
3494 	}
3495 
3496 	return 0;
3497 }
3498 
3499 /**
3500  *	gsmld_output		-	write to link
3501  *	@gsm: our mux
3502  *	@data: bytes to output
3503  *	@len: size
3504  *
3505  *	Write a block of data from the GSM mux to the data channel. This
3506  *	will eventually be serialized from above but at the moment isn't.
3507  */
3508 
gsmld_output(struct gsm_mux * gsm,u8 * data,int len)3509 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
3510 {
3511 	if (tty_write_room(gsm->tty) < len) {
3512 		set_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
3513 		return -ENOSPC;
3514 	}
3515 	if (debug & DBG_DATA)
3516 		gsm_hex_dump_bytes(__func__, data, len);
3517 	return gsm->tty->ops->write(gsm->tty, data, len);
3518 }
3519 
3520 
3521 /**
3522  *	gsmld_write_trigger	-	schedule ldisc write task
3523  *	@gsm: our mux
3524  */
gsmld_write_trigger(struct gsm_mux * gsm)3525 static void gsmld_write_trigger(struct gsm_mux *gsm)
3526 {
3527 	if (!gsm || !gsm->dlci[0] || gsm->dlci[0]->dead)
3528 		return;
3529 	schedule_work(&gsm->tx_work);
3530 }
3531 
3532 
3533 /**
3534  *	gsmld_write_task	-	ldisc write task
3535  *	@work: our tx write work
3536  *
3537  *	Writes out data to the ldisc if possible. We are doing this here to
3538  *	avoid dead-locking. This returns if no space or data is left for output.
3539  */
gsmld_write_task(struct work_struct * work)3540 static void gsmld_write_task(struct work_struct *work)
3541 {
3542 	struct gsm_mux *gsm = container_of(work, struct gsm_mux, tx_work);
3543 	unsigned long flags;
3544 	int i, ret;
3545 
3546 	/* All outstanding control channel and control messages and one data
3547 	 * frame is sent.
3548 	 */
3549 	ret = -ENODEV;
3550 	spin_lock_irqsave(&gsm->tx_lock, flags);
3551 	if (gsm->tty)
3552 		ret = gsm_data_kick(gsm);
3553 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
3554 
3555 	if (ret >= 0)
3556 		for (i = 0; i < NUM_DLCI; i++)
3557 			if (gsm->dlci[i])
3558 				tty_port_tty_wakeup(&gsm->dlci[i]->port);
3559 }
3560 
3561 /**
3562  *	gsmld_attach_gsm	-	mode set up
3563  *	@tty: our tty structure
3564  *	@gsm: our mux
3565  *
3566  *	Set up the MUX for basic mode and commence connecting to the
3567  *	modem. Currently called from the line discipline set up but
3568  *	will need moving to an ioctl path.
3569  */
3570 
gsmld_attach_gsm(struct tty_struct * tty,struct gsm_mux * gsm)3571 static void gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
3572 {
3573 	gsm->tty = tty_kref_get(tty);
3574 	/* Turn off tty XON/XOFF handling to handle it explicitly. */
3575 	gsm->old_c_iflag = tty->termios.c_iflag;
3576 	tty->termios.c_iflag &= (IXON | IXOFF);
3577 }
3578 
3579 /**
3580  *	gsmld_detach_gsm	-	stop doing 0710 mux
3581  *	@tty: tty attached to the mux
3582  *	@gsm: mux
3583  *
3584  *	Shutdown and then clean up the resources used by the line discipline
3585  */
3586 
gsmld_detach_gsm(struct tty_struct * tty,struct gsm_mux * gsm)3587 static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
3588 {
3589 	WARN_ON(tty != gsm->tty);
3590 	/* Restore tty XON/XOFF handling. */
3591 	gsm->tty->termios.c_iflag = gsm->old_c_iflag;
3592 	tty_kref_put(gsm->tty);
3593 	gsm->tty = NULL;
3594 }
3595 
gsmld_receive_buf(struct tty_struct * tty,const u8 * cp,const u8 * fp,size_t count)3596 static void gsmld_receive_buf(struct tty_struct *tty, const u8 *cp,
3597 			      const u8 *fp, size_t count)
3598 {
3599 	struct gsm_mux *gsm = tty->disc_data;
3600 	u8 flags = TTY_NORMAL;
3601 
3602 	if (debug & DBG_DATA)
3603 		gsm_hex_dump_bytes(__func__, cp, count);
3604 
3605 	for (; count; count--, cp++) {
3606 		if (fp)
3607 			flags = *fp++;
3608 		switch (flags) {
3609 		case TTY_NORMAL:
3610 			if (gsm->receive)
3611 				gsm->receive(gsm, *cp);
3612 			break;
3613 		case TTY_OVERRUN:
3614 		case TTY_BREAK:
3615 		case TTY_PARITY:
3616 		case TTY_FRAME:
3617 			gsm_error(gsm);
3618 			break;
3619 		default:
3620 			WARN_ONCE(1, "%s: unknown flag %d\n",
3621 			       tty_name(tty), flags);
3622 			break;
3623 		}
3624 	}
3625 	/* FASYNC if needed ? */
3626 	/* If clogged call tty_throttle(tty); */
3627 }
3628 
3629 /**
3630  *	gsmld_flush_buffer	-	clean input queue
3631  *	@tty:	terminal device
3632  *
3633  *	Flush the input buffer. Called when the line discipline is
3634  *	being closed, when the tty layer wants the buffer flushed (eg
3635  *	at hangup).
3636  */
3637 
gsmld_flush_buffer(struct tty_struct * tty)3638 static void gsmld_flush_buffer(struct tty_struct *tty)
3639 {
3640 }
3641 
3642 /**
3643  *	gsmld_close		-	close the ldisc for this tty
3644  *	@tty: device
3645  *
3646  *	Called from the terminal layer when this line discipline is
3647  *	being shut down, either because of a close or becsuse of a
3648  *	discipline change. The function will not be called while other
3649  *	ldisc methods are in progress.
3650  */
3651 
gsmld_close(struct tty_struct * tty)3652 static void gsmld_close(struct tty_struct *tty)
3653 {
3654 	struct gsm_mux *gsm = tty->disc_data;
3655 
3656 	/* The ldisc locks and closes the port before calling our close. This
3657 	 * means we have no way to do a proper disconnect. We will not bother
3658 	 * to do one.
3659 	 */
3660 	gsm_cleanup_mux(gsm, false);
3661 
3662 	gsmld_detach_gsm(tty, gsm);
3663 
3664 	gsmld_flush_buffer(tty);
3665 	/* Do other clean up here */
3666 	mux_put(gsm);
3667 }
3668 
3669 /**
3670  *	gsmld_open		-	open an ldisc
3671  *	@tty: terminal to open
3672  *
3673  *	Called when this line discipline is being attached to the
3674  *	terminal device. Can sleep. Called serialized so that no
3675  *	other events will occur in parallel. No further open will occur
3676  *	until a close.
3677  */
3678 
gsmld_open(struct tty_struct * tty)3679 static int gsmld_open(struct tty_struct *tty)
3680 {
3681 	struct gsm_mux *gsm;
3682 
3683 	if (!capable(CAP_NET_ADMIN))
3684 		return -EPERM;
3685 
3686 	if (tty->ops->write == NULL)
3687 		return -EINVAL;
3688 
3689 	/* Attach our ldisc data */
3690 	gsm = gsm_alloc_mux();
3691 	if (gsm == NULL)
3692 		return -ENOMEM;
3693 
3694 	tty->disc_data = gsm;
3695 	tty->receive_room = 65536;
3696 
3697 	/* Attach the initial passive connection */
3698 	gsmld_attach_gsm(tty, gsm);
3699 
3700 	/* The mux will not be activated yet, we wait for correct
3701 	 * configuration first.
3702 	 */
3703 	if (gsm->encoding == GSM_BASIC_OPT)
3704 		gsm->receive = gsm0_receive;
3705 	else
3706 		gsm->receive = gsm1_receive;
3707 
3708 	return 0;
3709 }
3710 
3711 /**
3712  *	gsmld_write_wakeup	-	asynchronous I/O notifier
3713  *	@tty: tty device
3714  *
3715  *	Required for the ptys, serial driver etc. since processes
3716  *	that attach themselves to the master and rely on ASYNC
3717  *	IO must be woken up
3718  */
3719 
gsmld_write_wakeup(struct tty_struct * tty)3720 static void gsmld_write_wakeup(struct tty_struct *tty)
3721 {
3722 	struct gsm_mux *gsm = tty->disc_data;
3723 
3724 	/* Queue poll */
3725 	gsmld_write_trigger(gsm);
3726 }
3727 
3728 /**
3729  *	gsmld_read		-	read function for tty
3730  *	@tty: tty device
3731  *	@file: file object
3732  *	@buf: userspace buffer pointer
3733  *	@nr: size of I/O
3734  *	@cookie: unused
3735  *	@offset: unused
3736  *
3737  *	Perform reads for the line discipline. We are guaranteed that the
3738  *	line discipline will not be closed under us but we may get multiple
3739  *	parallel readers and must handle this ourselves. We may also get
3740  *	a hangup. Always called in user context, may sleep.
3741  *
3742  *	This code must be sure never to sleep through a hangup.
3743  */
3744 
gsmld_read(struct tty_struct * tty,struct file * file,u8 * buf,size_t nr,void ** cookie,unsigned long offset)3745 static ssize_t gsmld_read(struct tty_struct *tty, struct file *file, u8 *buf,
3746 			  size_t nr, void **cookie, unsigned long offset)
3747 {
3748 	return -EOPNOTSUPP;
3749 }
3750 
3751 /**
3752  *	gsmld_write		-	write function for tty
3753  *	@tty: tty device
3754  *	@file: file object
3755  *	@buf: userspace buffer pointer
3756  *	@nr: size of I/O
3757  *
3758  *	Called when the owner of the device wants to send a frame
3759  *	itself (or some other control data). The data is transferred
3760  *	as-is and must be properly framed and checksummed as appropriate
3761  *	by userspace. Frames are either sent whole or not at all as this
3762  *	avoids pain user side.
3763  */
3764 
gsmld_write(struct tty_struct * tty,struct file * file,const u8 * buf,size_t nr)3765 static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
3766 			   const u8 *buf, size_t nr)
3767 {
3768 	struct gsm_mux *gsm = tty->disc_data;
3769 	unsigned long flags;
3770 	size_t space;
3771 	int ret;
3772 
3773 	if (!gsm)
3774 		return -ENODEV;
3775 
3776 	ret = -ENOBUFS;
3777 	spin_lock_irqsave(&gsm->tx_lock, flags);
3778 	space = tty_write_room(tty);
3779 	if (space >= nr)
3780 		ret = tty->ops->write(tty, buf, nr);
3781 	else
3782 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
3783 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
3784 
3785 	return ret;
3786 }
3787 
3788 /**
3789  *	gsmld_poll		-	poll method for N_GSM0710
3790  *	@tty: terminal device
3791  *	@file: file accessing it
3792  *	@wait: poll table
3793  *
3794  *	Called when the line discipline is asked to poll() for data or
3795  *	for special events. This code is not serialized with respect to
3796  *	other events save open/close.
3797  *
3798  *	This code must be sure never to sleep through a hangup.
3799  *	Called without the kernel lock held - fine
3800  */
3801 
gsmld_poll(struct tty_struct * tty,struct file * file,poll_table * wait)3802 static __poll_t gsmld_poll(struct tty_struct *tty, struct file *file,
3803 							poll_table *wait)
3804 {
3805 	__poll_t mask = 0;
3806 	struct gsm_mux *gsm = tty->disc_data;
3807 
3808 	poll_wait(file, &tty->read_wait, wait);
3809 	poll_wait(file, &tty->write_wait, wait);
3810 
3811 	if (gsm->dead)
3812 		mask |= EPOLLHUP;
3813 	if (tty_hung_up_p(file))
3814 		mask |= EPOLLHUP;
3815 	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
3816 		mask |= EPOLLHUP;
3817 	if (!tty_is_writelocked(tty) && tty_write_room(tty) > 0)
3818 		mask |= EPOLLOUT | EPOLLWRNORM;
3819 	return mask;
3820 }
3821 
gsmld_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)3822 static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
3823 		       unsigned long arg)
3824 {
3825 	struct gsm_config c;
3826 	struct gsm_config_ext ce;
3827 	struct gsm_dlci_config dc;
3828 	struct gsm_mux *gsm = tty->disc_data;
3829 	unsigned int base, addr;
3830 	struct gsm_dlci *dlci;
3831 
3832 	switch (cmd) {
3833 	case GSMIOC_GETCONF:
3834 		gsm_copy_config_values(gsm, &c);
3835 		if (copy_to_user((void __user *)arg, &c, sizeof(c)))
3836 			return -EFAULT;
3837 		return 0;
3838 	case GSMIOC_SETCONF:
3839 		if (copy_from_user(&c, (void __user *)arg, sizeof(c)))
3840 			return -EFAULT;
3841 		return gsm_config(gsm, &c);
3842 	case GSMIOC_GETFIRST:
3843 		base = mux_num_to_base(gsm);
3844 		return put_user(base + 1, (__u32 __user *)arg);
3845 	case GSMIOC_GETCONF_EXT:
3846 		gsm_copy_config_ext_values(gsm, &ce);
3847 		if (copy_to_user((void __user *)arg, &ce, sizeof(ce)))
3848 			return -EFAULT;
3849 		return 0;
3850 	case GSMIOC_SETCONF_EXT:
3851 		if (copy_from_user(&ce, (void __user *)arg, sizeof(ce)))
3852 			return -EFAULT;
3853 		return gsm_config_ext(gsm, &ce);
3854 	case GSMIOC_GETCONF_DLCI:
3855 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
3856 			return -EFAULT;
3857 		if (dc.channel == 0 || dc.channel >= NUM_DLCI)
3858 			return -EINVAL;
3859 		addr = array_index_nospec(dc.channel, NUM_DLCI);
3860 		dlci = gsm->dlci[addr];
3861 		if (!dlci) {
3862 			dlci = gsm_dlci_alloc(gsm, addr);
3863 			if (!dlci)
3864 				return -ENOMEM;
3865 		}
3866 		gsm_dlci_copy_config_values(dlci, &dc);
3867 		if (copy_to_user((void __user *)arg, &dc, sizeof(dc)))
3868 			return -EFAULT;
3869 		return 0;
3870 	case GSMIOC_SETCONF_DLCI:
3871 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
3872 			return -EFAULT;
3873 		if (dc.channel == 0 || dc.channel >= NUM_DLCI)
3874 			return -EINVAL;
3875 		addr = array_index_nospec(dc.channel, NUM_DLCI);
3876 		dlci = gsm->dlci[addr];
3877 		if (!dlci) {
3878 			dlci = gsm_dlci_alloc(gsm, addr);
3879 			if (!dlci)
3880 				return -ENOMEM;
3881 		}
3882 		return gsm_dlci_config(dlci, &dc, 0);
3883 	default:
3884 		return n_tty_ioctl_helper(tty, cmd, arg);
3885 	}
3886 }
3887 
3888 /*
3889  *	Network interface
3890  *
3891  */
3892 
gsm_mux_net_open(struct net_device * net)3893 static int gsm_mux_net_open(struct net_device *net)
3894 {
3895 	pr_debug("%s called\n", __func__);
3896 	netif_start_queue(net);
3897 	return 0;
3898 }
3899 
gsm_mux_net_close(struct net_device * net)3900 static int gsm_mux_net_close(struct net_device *net)
3901 {
3902 	netif_stop_queue(net);
3903 	return 0;
3904 }
3905 
dlci_net_free(struct gsm_dlci * dlci)3906 static void dlci_net_free(struct gsm_dlci *dlci)
3907 {
3908 	if (!dlci->net) {
3909 		WARN_ON(1);
3910 		return;
3911 	}
3912 	dlci->adaption = dlci->prev_adaption;
3913 	dlci->data = dlci->prev_data;
3914 	free_netdev(dlci->net);
3915 	dlci->net = NULL;
3916 }
net_free(struct kref * ref)3917 static void net_free(struct kref *ref)
3918 {
3919 	struct gsm_mux_net *mux_net;
3920 	struct gsm_dlci *dlci;
3921 
3922 	mux_net = container_of(ref, struct gsm_mux_net, ref);
3923 	dlci = mux_net->dlci;
3924 
3925 	if (dlci->net) {
3926 		unregister_netdev(dlci->net);
3927 		dlci_net_free(dlci);
3928 	}
3929 }
3930 
muxnet_get(struct gsm_mux_net * mux_net)3931 static inline void muxnet_get(struct gsm_mux_net *mux_net)
3932 {
3933 	kref_get(&mux_net->ref);
3934 }
3935 
muxnet_put(struct gsm_mux_net * mux_net)3936 static inline void muxnet_put(struct gsm_mux_net *mux_net)
3937 {
3938 	kref_put(&mux_net->ref, net_free);
3939 }
3940 
gsm_mux_net_start_xmit(struct sk_buff * skb,struct net_device * net)3941 static netdev_tx_t gsm_mux_net_start_xmit(struct sk_buff *skb,
3942 				      struct net_device *net)
3943 {
3944 	struct gsm_mux_net *mux_net = netdev_priv(net);
3945 	struct gsm_dlci *dlci = mux_net->dlci;
3946 	muxnet_get(mux_net);
3947 
3948 	skb_queue_head(&dlci->skb_list, skb);
3949 	net->stats.tx_packets++;
3950 	net->stats.tx_bytes += skb->len;
3951 	gsm_dlci_data_kick(dlci);
3952 	/* And tell the kernel when the last transmit started. */
3953 	netif_trans_update(net);
3954 	muxnet_put(mux_net);
3955 	return NETDEV_TX_OK;
3956 }
3957 
3958 /* called when a packet did not ack after watchdogtimeout */
gsm_mux_net_tx_timeout(struct net_device * net,unsigned int txqueue)3959 static void gsm_mux_net_tx_timeout(struct net_device *net, unsigned int txqueue)
3960 {
3961 	/* Tell syslog we are hosed. */
3962 	dev_dbg(&net->dev, "Tx timed out.\n");
3963 
3964 	/* Update statistics */
3965 	net->stats.tx_errors++;
3966 }
3967 
gsm_mux_rx_netchar(struct gsm_dlci * dlci,const u8 * in_buf,int size)3968 static void gsm_mux_rx_netchar(struct gsm_dlci *dlci, const u8 *in_buf, int size)
3969 {
3970 	struct net_device *net = dlci->net;
3971 	struct sk_buff *skb;
3972 	struct gsm_mux_net *mux_net = netdev_priv(net);
3973 	muxnet_get(mux_net);
3974 
3975 	/* Allocate an sk_buff */
3976 	skb = dev_alloc_skb(size + NET_IP_ALIGN);
3977 	if (!skb) {
3978 		/* We got no receive buffer. */
3979 		net->stats.rx_dropped++;
3980 		muxnet_put(mux_net);
3981 		return;
3982 	}
3983 	skb_reserve(skb, NET_IP_ALIGN);
3984 	skb_put_data(skb, in_buf, size);
3985 
3986 	skb->dev = net;
3987 	skb->protocol = htons(ETH_P_IP);
3988 
3989 	/* Ship it off to the kernel */
3990 	netif_rx(skb);
3991 
3992 	/* update out statistics */
3993 	net->stats.rx_packets++;
3994 	net->stats.rx_bytes += size;
3995 	muxnet_put(mux_net);
3996 	return;
3997 }
3998 
gsm_mux_net_init(struct net_device * net)3999 static void gsm_mux_net_init(struct net_device *net)
4000 {
4001 	static const struct net_device_ops gsm_netdev_ops = {
4002 		.ndo_open		= gsm_mux_net_open,
4003 		.ndo_stop		= gsm_mux_net_close,
4004 		.ndo_start_xmit		= gsm_mux_net_start_xmit,
4005 		.ndo_tx_timeout		= gsm_mux_net_tx_timeout,
4006 	};
4007 
4008 	net->netdev_ops = &gsm_netdev_ops;
4009 
4010 	/* fill in the other fields */
4011 	net->watchdog_timeo = GSM_NET_TX_TIMEOUT;
4012 	net->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
4013 	net->type = ARPHRD_NONE;
4014 	net->tx_queue_len = 10;
4015 }
4016 
4017 
4018 /* caller holds the dlci mutex */
gsm_destroy_network(struct gsm_dlci * dlci)4019 static void gsm_destroy_network(struct gsm_dlci *dlci)
4020 {
4021 	struct gsm_mux_net *mux_net;
4022 
4023 	pr_debug("destroy network interface\n");
4024 	if (!dlci->net)
4025 		return;
4026 	mux_net = netdev_priv(dlci->net);
4027 	muxnet_put(mux_net);
4028 }
4029 
4030 
4031 /* caller holds the dlci mutex */
gsm_create_network(struct gsm_dlci * dlci,struct gsm_netconfig * nc)4032 static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc)
4033 {
4034 	char *netname;
4035 	int retval = 0;
4036 	struct net_device *net;
4037 	struct gsm_mux_net *mux_net;
4038 
4039 	if (!capable(CAP_NET_ADMIN))
4040 		return -EPERM;
4041 
4042 	/* Already in a non tty mode */
4043 	if (dlci->adaption > 2)
4044 		return -EBUSY;
4045 
4046 	if (nc->protocol != htons(ETH_P_IP))
4047 		return -EPROTONOSUPPORT;
4048 
4049 	if (nc->adaption != 3 && nc->adaption != 4)
4050 		return -EPROTONOSUPPORT;
4051 
4052 	pr_debug("create network interface\n");
4053 
4054 	netname = "gsm%d";
4055 	if (nc->if_name[0] != '\0')
4056 		netname = nc->if_name;
4057 	net = alloc_netdev(sizeof(struct gsm_mux_net), netname,
4058 			   NET_NAME_UNKNOWN, gsm_mux_net_init);
4059 	if (!net) {
4060 		pr_err("alloc_netdev failed\n");
4061 		return -ENOMEM;
4062 	}
4063 	net->mtu = dlci->mtu;
4064 	net->min_mtu = MIN_MTU;
4065 	net->max_mtu = dlci->mtu;
4066 	mux_net = netdev_priv(net);
4067 	mux_net->dlci = dlci;
4068 	kref_init(&mux_net->ref);
4069 	strscpy(nc->if_name, net->name); /* return net name */
4070 
4071 	/* reconfigure dlci for network */
4072 	dlci->prev_adaption = dlci->adaption;
4073 	dlci->prev_data = dlci->data;
4074 	dlci->adaption = nc->adaption;
4075 	dlci->data = gsm_mux_rx_netchar;
4076 	dlci->net = net;
4077 
4078 	pr_debug("register netdev\n");
4079 	retval = register_netdev(net);
4080 	if (retval) {
4081 		pr_err("network register fail %d\n", retval);
4082 		dlci_net_free(dlci);
4083 		return retval;
4084 	}
4085 	return net->ifindex;	/* return network index */
4086 }
4087 
4088 /* Line discipline for real tty */
4089 static struct tty_ldisc_ops tty_ldisc_packet = {
4090 	.owner		 = THIS_MODULE,
4091 	.num		 = N_GSM0710,
4092 	.name            = "n_gsm",
4093 	.open            = gsmld_open,
4094 	.close           = gsmld_close,
4095 	.flush_buffer    = gsmld_flush_buffer,
4096 	.read            = gsmld_read,
4097 	.write           = gsmld_write,
4098 	.ioctl           = gsmld_ioctl,
4099 	.poll            = gsmld_poll,
4100 	.receive_buf     = gsmld_receive_buf,
4101 	.write_wakeup    = gsmld_write_wakeup
4102 };
4103 
4104 /*
4105  *	Virtual tty side
4106  */
4107 
4108 /**
4109  *	gsm_modem_upd_via_data	-	send modem bits via convergence layer
4110  *	@dlci: channel
4111  *	@brk: break signal
4112  *
4113  *	Send an empty frame to signal mobile state changes and to transmit the
4114  *	break signal for adaption 2.
4115  */
4116 
gsm_modem_upd_via_data(struct gsm_dlci * dlci,u8 brk)4117 static void gsm_modem_upd_via_data(struct gsm_dlci *dlci, u8 brk)
4118 {
4119 	struct gsm_mux *gsm = dlci->gsm;
4120 	unsigned long flags;
4121 
4122 	if (dlci->state != DLCI_OPEN || dlci->adaption != 2)
4123 		return;
4124 
4125 	spin_lock_irqsave(&gsm->tx_lock, flags);
4126 	gsm_dlci_modem_output(gsm, dlci, brk);
4127 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
4128 }
4129 
4130 /**
4131  *	gsm_modem_upd_via_msc	-	send modem bits via control frame
4132  *	@dlci: channel
4133  *	@brk: break signal
4134  */
4135 
gsm_modem_upd_via_msc(struct gsm_dlci * dlci,u8 brk)4136 static int gsm_modem_upd_via_msc(struct gsm_dlci *dlci, u8 brk)
4137 {
4138 	u8 modembits[3];
4139 	struct gsm_control *ctrl;
4140 	int len = 2;
4141 
4142 	if (dlci->gsm->encoding != GSM_BASIC_OPT)
4143 		return 0;
4144 
4145 	modembits[0] = (dlci->addr << 2) | 2 | EA;  /* DLCI, Valid, EA */
4146 	if (!brk) {
4147 		modembits[1] = (gsm_encode_modem(dlci) << 1) | EA;
4148 	} else {
4149 		modembits[1] = gsm_encode_modem(dlci) << 1;
4150 		modembits[2] = (brk << 4) | 2 | EA; /* Length, Break, EA */
4151 		len++;
4152 	}
4153 	ctrl = gsm_control_send(dlci->gsm, CMD_MSC, modembits, len);
4154 	if (ctrl == NULL)
4155 		return -ENOMEM;
4156 	return gsm_control_wait(dlci->gsm, ctrl);
4157 }
4158 
4159 /**
4160  *	gsm_modem_update	-	send modem status line state
4161  *	@dlci: channel
4162  *	@brk: break signal
4163  */
4164 
gsm_modem_update(struct gsm_dlci * dlci,u8 brk)4165 static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk)
4166 {
4167 	if (dlci->gsm->dead)
4168 		return -EL2HLT;
4169 	if (dlci->adaption == 2) {
4170 		/* Send convergence layer type 2 empty data frame. */
4171 		gsm_modem_upd_via_data(dlci, brk);
4172 		return 0;
4173 	} else if (dlci->gsm->encoding == GSM_BASIC_OPT) {
4174 		/* Send as MSC control message. */
4175 		return gsm_modem_upd_via_msc(dlci, brk);
4176 	}
4177 
4178 	/* Modem status lines are not supported. */
4179 	return -EPROTONOSUPPORT;
4180 }
4181 
4182 /**
4183  * gsm_wait_modem_change - wait for modem status line change
4184  * @dlci: channel
4185  * @mask: modem status line bits
4186  *
4187  * The function returns if:
4188  * - any given modem status line bit changed
4189  * - the wait event function got interrupted (e.g. by a signal)
4190  * - the underlying DLCI was closed
4191  * - the underlying ldisc device was removed
4192  */
gsm_wait_modem_change(struct gsm_dlci * dlci,u32 mask)4193 static int gsm_wait_modem_change(struct gsm_dlci *dlci, u32 mask)
4194 {
4195 	struct gsm_mux *gsm = dlci->gsm;
4196 	u32 old = dlci->modem_rx;
4197 	int ret;
4198 
4199 	ret = wait_event_interruptible(gsm->event, gsm->dead ||
4200 				       dlci->state != DLCI_OPEN ||
4201 				       (old ^ dlci->modem_rx) & mask);
4202 	if (gsm->dead)
4203 		return -ENODEV;
4204 	if (dlci->state != DLCI_OPEN)
4205 		return -EL2NSYNC;
4206 	return ret;
4207 }
4208 
gsm_carrier_raised(struct tty_port * port)4209 static bool gsm_carrier_raised(struct tty_port *port)
4210 {
4211 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
4212 	struct gsm_mux *gsm = dlci->gsm;
4213 
4214 	/* Not yet open so no carrier info */
4215 	if (dlci->state != DLCI_OPEN)
4216 		return false;
4217 	if (debug & DBG_CD_ON)
4218 		return true;
4219 
4220 	/*
4221 	 * Basic mode with control channel in ADM mode may not respond
4222 	 * to CMD_MSC at all and modem_rx is empty.
4223 	 */
4224 	if (gsm->encoding == GSM_BASIC_OPT &&
4225 	    gsm->dlci[0]->mode == DLCI_MODE_ADM && !dlci->modem_rx)
4226 		return true;
4227 
4228 	return dlci->modem_rx & TIOCM_CD;
4229 }
4230 
gsm_dtr_rts(struct tty_port * port,bool active)4231 static void gsm_dtr_rts(struct tty_port *port, bool active)
4232 {
4233 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
4234 	unsigned int modem_tx = dlci->modem_tx;
4235 	if (active)
4236 		modem_tx |= TIOCM_DTR | TIOCM_RTS;
4237 	else
4238 		modem_tx &= ~(TIOCM_DTR | TIOCM_RTS);
4239 	if (modem_tx != dlci->modem_tx) {
4240 		dlci->modem_tx = modem_tx;
4241 		gsm_modem_update(dlci, 0);
4242 	}
4243 }
4244 
4245 static const struct tty_port_operations gsm_port_ops = {
4246 	.carrier_raised = gsm_carrier_raised,
4247 	.dtr_rts = gsm_dtr_rts,
4248 	.destruct = gsm_dlci_free,
4249 };
4250 
gsmtty_install(struct tty_driver * driver,struct tty_struct * tty)4251 static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
4252 {
4253 	struct gsm_mux *gsm;
4254 	struct gsm_dlci *dlci;
4255 	unsigned int line = tty->index;
4256 	unsigned int mux = mux_line_to_num(line);
4257 	bool alloc = false;
4258 	int ret;
4259 
4260 	line = line & 0x3F;
4261 
4262 	if (mux >= MAX_MUX)
4263 		return -ENXIO;
4264 	/* FIXME: we need to lock gsm_mux for lifetimes of ttys eventually */
4265 	if (gsm_mux[mux] == NULL)
4266 		return -EUNATCH;
4267 	if (line == 0 || line > 61)	/* 62/63 reserved */
4268 		return -ECHRNG;
4269 	gsm = gsm_mux[mux];
4270 	if (gsm->dead)
4271 		return -EL2HLT;
4272 	/* If DLCI 0 is not yet fully open return an error.
4273 	This is ok from a locking
4274 	perspective as we don't have to worry about this
4275 	if DLCI0 is lost */
4276 	mutex_lock(&gsm->mutex);
4277 	if (gsm->dlci[0] && gsm->dlci[0]->state != DLCI_OPEN) {
4278 		mutex_unlock(&gsm->mutex);
4279 		return -EL2NSYNC;
4280 	}
4281 	dlci = gsm->dlci[line];
4282 	if (dlci == NULL) {
4283 		alloc = true;
4284 		dlci = gsm_dlci_alloc(gsm, line);
4285 	}
4286 	if (dlci == NULL) {
4287 		mutex_unlock(&gsm->mutex);
4288 		return -ENOMEM;
4289 	}
4290 	ret = tty_port_install(&dlci->port, driver, tty);
4291 	if (ret) {
4292 		if (alloc)
4293 			dlci_put(dlci);
4294 		mutex_unlock(&gsm->mutex);
4295 		return ret;
4296 	}
4297 
4298 	dlci_get(dlci);
4299 	dlci_get(gsm->dlci[0]);
4300 	mux_get(gsm);
4301 	tty->driver_data = dlci;
4302 	mutex_unlock(&gsm->mutex);
4303 
4304 	return 0;
4305 }
4306 
gsmtty_open(struct tty_struct * tty,struct file * filp)4307 static int gsmtty_open(struct tty_struct *tty, struct file *filp)
4308 {
4309 	struct gsm_dlci *dlci = tty->driver_data;
4310 	struct tty_port *port = &dlci->port;
4311 
4312 	port->count++;
4313 	tty_port_tty_set(port, tty);
4314 
4315 	dlci->modem_rx = 0;
4316 	/* We could in theory open and close before we wait - eg if we get
4317 	   a DM straight back. This is ok as that will have caused a hangup */
4318 	tty_port_set_initialized(port, true);
4319 	/* Start sending off SABM messages */
4320 	if (!dlci->gsm->wait_config) {
4321 		/* Start sending off SABM messages */
4322 		if (dlci->gsm->initiator)
4323 			gsm_dlci_begin_open(dlci);
4324 		else
4325 			gsm_dlci_set_opening(dlci);
4326 	} else {
4327 		gsm_dlci_set_wait_config(dlci);
4328 	}
4329 	/* And wait for virtual carrier */
4330 	return tty_port_block_til_ready(port, tty, filp);
4331 }
4332 
gsmtty_close(struct tty_struct * tty,struct file * filp)4333 static void gsmtty_close(struct tty_struct *tty, struct file *filp)
4334 {
4335 	struct gsm_dlci *dlci = tty->driver_data;
4336 
4337 	if (dlci == NULL)
4338 		return;
4339 	if (dlci->state == DLCI_CLOSED)
4340 		return;
4341 	mutex_lock(&dlci->mutex);
4342 	gsm_destroy_network(dlci);
4343 	mutex_unlock(&dlci->mutex);
4344 	if (tty_port_close_start(&dlci->port, tty, filp) == 0)
4345 		return;
4346 	gsm_dlci_begin_close(dlci);
4347 	if (tty_port_initialized(&dlci->port) && C_HUPCL(tty))
4348 		tty_port_lower_dtr_rts(&dlci->port);
4349 	tty_port_close_end(&dlci->port, tty);
4350 	tty_port_tty_set(&dlci->port, NULL);
4351 	return;
4352 }
4353 
gsmtty_hangup(struct tty_struct * tty)4354 static void gsmtty_hangup(struct tty_struct *tty)
4355 {
4356 	struct gsm_dlci *dlci = tty->driver_data;
4357 	if (dlci->state == DLCI_CLOSED)
4358 		return;
4359 	tty_port_hangup(&dlci->port);
4360 	gsm_dlci_begin_close(dlci);
4361 }
4362 
gsmtty_write(struct tty_struct * tty,const u8 * buf,size_t len)4363 static ssize_t gsmtty_write(struct tty_struct *tty, const u8 *buf, size_t len)
4364 {
4365 	int sent;
4366 	struct gsm_dlci *dlci = tty->driver_data;
4367 	if (dlci->state == DLCI_CLOSED)
4368 		return -EINVAL;
4369 	/* Stuff the bytes into the fifo queue */
4370 	sent = kfifo_in_locked(&dlci->fifo, buf, len, &dlci->lock);
4371 	/* Need to kick the channel */
4372 	gsm_dlci_data_kick(dlci);
4373 	return sent;
4374 }
4375 
gsmtty_write_room(struct tty_struct * tty)4376 static unsigned int gsmtty_write_room(struct tty_struct *tty)
4377 {
4378 	struct gsm_dlci *dlci = tty->driver_data;
4379 	if (dlci->state == DLCI_CLOSED)
4380 		return 0;
4381 	return kfifo_avail(&dlci->fifo);
4382 }
4383 
gsmtty_chars_in_buffer(struct tty_struct * tty)4384 static unsigned int gsmtty_chars_in_buffer(struct tty_struct *tty)
4385 {
4386 	struct gsm_dlci *dlci = tty->driver_data;
4387 	if (dlci->state == DLCI_CLOSED)
4388 		return 0;
4389 	return kfifo_len(&dlci->fifo);
4390 }
4391 
gsmtty_flush_buffer(struct tty_struct * tty)4392 static void gsmtty_flush_buffer(struct tty_struct *tty)
4393 {
4394 	struct gsm_dlci *dlci = tty->driver_data;
4395 	unsigned long flags;
4396 
4397 	if (dlci->state == DLCI_CLOSED)
4398 		return;
4399 	/* Caution needed: If we implement reliable transport classes
4400 	   then the data being transmitted can't simply be junked once
4401 	   it has first hit the stack. Until then we can just blow it
4402 	   away */
4403 	spin_lock_irqsave(&dlci->lock, flags);
4404 	kfifo_reset(&dlci->fifo);
4405 	spin_unlock_irqrestore(&dlci->lock, flags);
4406 	/* Need to unhook this DLCI from the transmit queue logic */
4407 }
4408 
gsmtty_wait_until_sent(struct tty_struct * tty,int timeout)4409 static void gsmtty_wait_until_sent(struct tty_struct *tty, int timeout)
4410 {
4411 	/* The FIFO handles the queue so the kernel will do the right
4412 	   thing waiting on chars_in_buffer before calling us. No work
4413 	   to do here */
4414 }
4415 
gsmtty_tiocmget(struct tty_struct * tty)4416 static int gsmtty_tiocmget(struct tty_struct *tty)
4417 {
4418 	struct gsm_dlci *dlci = tty->driver_data;
4419 	if (dlci->state == DLCI_CLOSED)
4420 		return -EINVAL;
4421 	return dlci->modem_rx;
4422 }
4423 
gsmtty_tiocmset(struct tty_struct * tty,unsigned int set,unsigned int clear)4424 static int gsmtty_tiocmset(struct tty_struct *tty,
4425 	unsigned int set, unsigned int clear)
4426 {
4427 	struct gsm_dlci *dlci = tty->driver_data;
4428 	unsigned int modem_tx = dlci->modem_tx;
4429 
4430 	if (dlci->state == DLCI_CLOSED)
4431 		return -EINVAL;
4432 	modem_tx &= ~clear;
4433 	modem_tx |= set;
4434 
4435 	if (modem_tx != dlci->modem_tx) {
4436 		dlci->modem_tx = modem_tx;
4437 		return gsm_modem_update(dlci, 0);
4438 	}
4439 	return 0;
4440 }
4441 
4442 
gsmtty_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)4443 static int gsmtty_ioctl(struct tty_struct *tty,
4444 			unsigned int cmd, unsigned long arg)
4445 {
4446 	struct gsm_dlci *dlci = tty->driver_data;
4447 	struct gsm_netconfig nc;
4448 	struct gsm_dlci_config dc;
4449 	int index;
4450 
4451 	if (dlci->state == DLCI_CLOSED)
4452 		return -EINVAL;
4453 	switch (cmd) {
4454 	case GSMIOC_ENABLE_NET:
4455 		if (copy_from_user(&nc, (void __user *)arg, sizeof(nc)))
4456 			return -EFAULT;
4457 		nc.if_name[IFNAMSIZ-1] = '\0';
4458 		/* return net interface index or error code */
4459 		mutex_lock(&dlci->mutex);
4460 		index = gsm_create_network(dlci, &nc);
4461 		mutex_unlock(&dlci->mutex);
4462 		if (copy_to_user((void __user *)arg, &nc, sizeof(nc)))
4463 			return -EFAULT;
4464 		return index;
4465 	case GSMIOC_DISABLE_NET:
4466 		if (!capable(CAP_NET_ADMIN))
4467 			return -EPERM;
4468 		mutex_lock(&dlci->mutex);
4469 		gsm_destroy_network(dlci);
4470 		mutex_unlock(&dlci->mutex);
4471 		return 0;
4472 	case GSMIOC_GETCONF_DLCI:
4473 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
4474 			return -EFAULT;
4475 		if (dc.channel != dlci->addr)
4476 			return -EPERM;
4477 		gsm_dlci_copy_config_values(dlci, &dc);
4478 		if (copy_to_user((void __user *)arg, &dc, sizeof(dc)))
4479 			return -EFAULT;
4480 		return 0;
4481 	case GSMIOC_SETCONF_DLCI:
4482 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
4483 			return -EFAULT;
4484 		if (dc.channel >= NUM_DLCI)
4485 			return -EINVAL;
4486 		if (dc.channel != 0 && dc.channel != dlci->addr)
4487 			return -EPERM;
4488 		return gsm_dlci_config(dlci, &dc, 1);
4489 	case TIOCMIWAIT:
4490 		return gsm_wait_modem_change(dlci, (u32)arg);
4491 	default:
4492 		return -ENOIOCTLCMD;
4493 	}
4494 }
4495 
gsmtty_set_termios(struct tty_struct * tty,const struct ktermios * old)4496 static void gsmtty_set_termios(struct tty_struct *tty,
4497 			       const struct ktermios *old)
4498 {
4499 	struct gsm_dlci *dlci = tty->driver_data;
4500 	if (dlci->state == DLCI_CLOSED)
4501 		return;
4502 	/* For the moment its fixed. In actual fact the speed information
4503 	   for the virtual channel can be propogated in both directions by
4504 	   the RPN control message. This however rapidly gets nasty as we
4505 	   then have to remap modem signals each way according to whether
4506 	   our virtual cable is null modem etc .. */
4507 	tty_termios_copy_hw(&tty->termios, old);
4508 }
4509 
gsmtty_throttle(struct tty_struct * tty)4510 static void gsmtty_throttle(struct tty_struct *tty)
4511 {
4512 	struct gsm_dlci *dlci = tty->driver_data;
4513 	if (dlci->state == DLCI_CLOSED)
4514 		return;
4515 	if (C_CRTSCTS(tty))
4516 		dlci->modem_tx &= ~TIOCM_RTS;
4517 	dlci->throttled = true;
4518 	/* Send an MSC with RTS cleared */
4519 	gsm_modem_update(dlci, 0);
4520 }
4521 
gsmtty_unthrottle(struct tty_struct * tty)4522 static void gsmtty_unthrottle(struct tty_struct *tty)
4523 {
4524 	struct gsm_dlci *dlci = tty->driver_data;
4525 	if (dlci->state == DLCI_CLOSED)
4526 		return;
4527 	if (C_CRTSCTS(tty))
4528 		dlci->modem_tx |= TIOCM_RTS;
4529 	dlci->throttled = false;
4530 	/* Send an MSC with RTS set */
4531 	gsm_modem_update(dlci, 0);
4532 }
4533 
gsmtty_break_ctl(struct tty_struct * tty,int state)4534 static int gsmtty_break_ctl(struct tty_struct *tty, int state)
4535 {
4536 	struct gsm_dlci *dlci = tty->driver_data;
4537 	int encode = 0;	/* Off */
4538 	if (dlci->state == DLCI_CLOSED)
4539 		return -EINVAL;
4540 
4541 	if (state == -1)	/* "On indefinitely" - we can't encode this
4542 				    properly */
4543 		encode = 0x0F;
4544 	else if (state > 0) {
4545 		encode = state / 200;	/* mS to encoding */
4546 		if (encode > 0x0F)
4547 			encode = 0x0F;	/* Best effort */
4548 	}
4549 	return gsm_modem_update(dlci, encode);
4550 }
4551 
gsmtty_cleanup(struct tty_struct * tty)4552 static void gsmtty_cleanup(struct tty_struct *tty)
4553 {
4554 	struct gsm_dlci *dlci = tty->driver_data;
4555 	struct gsm_mux *gsm = dlci->gsm;
4556 
4557 	dlci_put(dlci);
4558 	dlci_put(gsm->dlci[0]);
4559 	mux_put(gsm);
4560 }
4561 
4562 /* Virtual ttys for the demux */
4563 static const struct tty_operations gsmtty_ops = {
4564 	.install		= gsmtty_install,
4565 	.open			= gsmtty_open,
4566 	.close			= gsmtty_close,
4567 	.write			= gsmtty_write,
4568 	.write_room		= gsmtty_write_room,
4569 	.chars_in_buffer	= gsmtty_chars_in_buffer,
4570 	.flush_buffer		= gsmtty_flush_buffer,
4571 	.ioctl			= gsmtty_ioctl,
4572 	.throttle		= gsmtty_throttle,
4573 	.unthrottle		= gsmtty_unthrottle,
4574 	.set_termios		= gsmtty_set_termios,
4575 	.hangup			= gsmtty_hangup,
4576 	.wait_until_sent	= gsmtty_wait_until_sent,
4577 	.tiocmget		= gsmtty_tiocmget,
4578 	.tiocmset		= gsmtty_tiocmset,
4579 	.break_ctl		= gsmtty_break_ctl,
4580 	.cleanup		= gsmtty_cleanup,
4581 };
4582 
4583 
4584 
gsm_init(void)4585 static int __init gsm_init(void)
4586 {
4587 	/* Fill in our line protocol discipline, and register it */
4588 	int status = tty_register_ldisc(&tty_ldisc_packet);
4589 	if (status != 0) {
4590 		pr_err("n_gsm: can't register line discipline (err = %d)\n",
4591 								status);
4592 		return status;
4593 	}
4594 
4595 	gsm_tty_driver = tty_alloc_driver(GSM_TTY_MINORS, TTY_DRIVER_REAL_RAW |
4596 			TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_HARDWARE_BREAK);
4597 	if (IS_ERR(gsm_tty_driver)) {
4598 		pr_err("gsm_init: tty allocation failed.\n");
4599 		status = PTR_ERR(gsm_tty_driver);
4600 		goto err_unreg_ldisc;
4601 	}
4602 	gsm_tty_driver->driver_name	= "gsmtty";
4603 	gsm_tty_driver->name		= "gsmtty";
4604 	gsm_tty_driver->major		= 0;	/* Dynamic */
4605 	gsm_tty_driver->minor_start	= 0;
4606 	gsm_tty_driver->type		= TTY_DRIVER_TYPE_SERIAL;
4607 	gsm_tty_driver->subtype	= SERIAL_TYPE_NORMAL;
4608 	gsm_tty_driver->init_termios	= tty_std_termios;
4609 	/* Fixme */
4610 	gsm_tty_driver->init_termios.c_lflag &= ~ECHO;
4611 	tty_set_operations(gsm_tty_driver, &gsmtty_ops);
4612 
4613 	if (tty_register_driver(gsm_tty_driver)) {
4614 		pr_err("gsm_init: tty registration failed.\n");
4615 		status = -EBUSY;
4616 		goto err_put_driver;
4617 	}
4618 	pr_debug("gsm_init: loaded as %d,%d.\n",
4619 			gsm_tty_driver->major, gsm_tty_driver->minor_start);
4620 	return 0;
4621 err_put_driver:
4622 	tty_driver_kref_put(gsm_tty_driver);
4623 err_unreg_ldisc:
4624 	tty_unregister_ldisc(&tty_ldisc_packet);
4625 	return status;
4626 }
4627 
gsm_exit(void)4628 static void __exit gsm_exit(void)
4629 {
4630 	tty_unregister_ldisc(&tty_ldisc_packet);
4631 	tty_unregister_driver(gsm_tty_driver);
4632 	tty_driver_kref_put(gsm_tty_driver);
4633 }
4634 
4635 module_init(gsm_init);
4636 module_exit(gsm_exit);
4637 
4638 
4639 MODULE_DESCRIPTION("GSM 0710 tty multiplexor");
4640 MODULE_LICENSE("GPL");
4641 MODULE_ALIAS_LDISC(N_GSM0710);
4642