xref: /linux/drivers/tty/n_gsm.c (revision 58f504efcda54a9079a38203acc088c3354aaa60)
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 
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 
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 
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  */
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 
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 
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  */
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  */
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  */
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 
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 
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  */
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  */
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 
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 
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 
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  */
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  */
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  */
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 
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 
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 
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 
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 
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 
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 
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  */
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 
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 
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  */
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 
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  */
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 
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 
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 
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 
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 
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 
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 
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 
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 
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 
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  */
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 receives DM.
2228  */
2229 
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->addr && gsm->control == (DM | PF)) {
2247 			if (debug & DBG_ERRORS)
2248 				pr_info("DLCI 0 opening in ADM mode.\n");
2249 			dlci->mode = DLCI_MODE_ADM;
2250 			gsm_dlci_open(dlci);
2251 		} else if (dlci->retries) {
2252 			if (!dlci->addr || !gsm->dlci[0] ||
2253 			    gsm->dlci[0]->state != DLCI_OPENING) {
2254 				dlci->retries--;
2255 				gsm_command(dlci->gsm, dlci->addr, SABM|PF);
2256 			}
2257 
2258 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2259 		} else {
2260 			gsm->open_error++;
2261 			gsm_dlci_begin_close(dlci); /* prevent half open link */
2262 		}
2263 
2264 		break;
2265 	case DLCI_CLOSING:
2266 		if (dlci->retries) {
2267 			dlci->retries--;
2268 			gsm_command(dlci->gsm, dlci->addr, DISC|PF);
2269 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2270 		} else
2271 			gsm_dlci_close(dlci);
2272 		break;
2273 	default:
2274 		pr_debug("%s: unhandled state: %d\n", __func__, dlci->state);
2275 		break;
2276 	}
2277 }
2278 
2279 /**
2280  *	gsm_dlci_begin_open	-	start channel open procedure
2281  *	@dlci: DLCI to open
2282  *
2283  *	Commence opening a DLCI from the Linux side. We issue SABM messages
2284  *	to the modem which should then reply with a UA or ADM, at which point
2285  *	we will move into open state. Opening is done asynchronously with retry
2286  *	running off timers and the responses.
2287  *	Parameter negotiation is performed before SABM if required.
2288  */
2289 
2290 static void gsm_dlci_begin_open(struct gsm_dlci *dlci)
2291 {
2292 	struct gsm_mux *gsm = dlci ? dlci->gsm : NULL;
2293 	bool need_pn = false;
2294 
2295 	if (!gsm)
2296 		return;
2297 
2298 	if (dlci->addr != 0) {
2299 		if (gsm->adaption != 1 || gsm->adaption != dlci->adaption)
2300 			need_pn = true;
2301 		if (dlci->prio != (roundup(dlci->addr + 1, 8) - 1))
2302 			need_pn = true;
2303 		if (gsm->ftype != dlci->ftype)
2304 			need_pn = true;
2305 	}
2306 
2307 	switch (dlci->state) {
2308 	case DLCI_CLOSED:
2309 	case DLCI_WAITING_CONFIG:
2310 	case DLCI_CLOSING:
2311 		dlci->retries = gsm->n2;
2312 		if (!need_pn) {
2313 			dlci->state = DLCI_OPENING;
2314 			if (!dlci->addr || !gsm->dlci[0] ||
2315 			    gsm->dlci[0]->state != DLCI_OPENING)
2316 				gsm_command(gsm, dlci->addr, SABM|PF);
2317 		} else {
2318 			/* Configure DLCI before setup */
2319 			dlci->state = DLCI_CONFIGURE;
2320 			if (gsm_dlci_negotiate(dlci) != 0) {
2321 				gsm_dlci_close(dlci);
2322 				return;
2323 			}
2324 		}
2325 		mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2326 		break;
2327 	default:
2328 		break;
2329 	}
2330 }
2331 
2332 /**
2333  *	gsm_dlci_set_opening	-	change state to opening
2334  *	@dlci: DLCI to open
2335  *
2336  *	Change internal state to wait for DLCI open from initiator side.
2337  *	We set off timers and responses upon reception of an SABM.
2338  */
2339 static void gsm_dlci_set_opening(struct gsm_dlci *dlci)
2340 {
2341 	switch (dlci->state) {
2342 	case DLCI_CLOSED:
2343 	case DLCI_WAITING_CONFIG:
2344 	case DLCI_CLOSING:
2345 		dlci->state = DLCI_OPENING;
2346 		break;
2347 	default:
2348 		break;
2349 	}
2350 }
2351 
2352 /**
2353  * gsm_dlci_set_wait_config	-	wait for channel configuration
2354  * @dlci: DLCI to configure
2355  *
2356  * Wait for a DLCI configuration from the application.
2357  */
2358 static void gsm_dlci_set_wait_config(struct gsm_dlci *dlci)
2359 {
2360 	switch (dlci->state) {
2361 	case DLCI_CLOSED:
2362 	case DLCI_CLOSING:
2363 		dlci->state = DLCI_WAITING_CONFIG;
2364 		break;
2365 	default:
2366 		break;
2367 	}
2368 }
2369 
2370 /**
2371  *	gsm_dlci_begin_close	-	start channel open procedure
2372  *	@dlci: DLCI to open
2373  *
2374  *	Commence closing a DLCI from the Linux side. We issue DISC messages
2375  *	to the modem which should then reply with a UA, at which point we
2376  *	will move into closed state. Closing is done asynchronously with retry
2377  *	off timers. We may also receive a DM reply from the other end which
2378  *	indicates the channel was already closed.
2379  */
2380 
2381 static void gsm_dlci_begin_close(struct gsm_dlci *dlci)
2382 {
2383 	struct gsm_mux *gsm = dlci->gsm;
2384 	if (dlci->state == DLCI_CLOSED || dlci->state == DLCI_CLOSING)
2385 		return;
2386 	dlci->retries = gsm->n2;
2387 	dlci->state = DLCI_CLOSING;
2388 	gsm_command(dlci->gsm, dlci->addr, DISC|PF);
2389 	mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
2390 	wake_up_interruptible(&gsm->event);
2391 }
2392 
2393 /**
2394  *	gsm_dlci_data		-	data arrived
2395  *	@dlci: channel
2396  *	@data: block of bytes received
2397  *	@clen: length of received block
2398  *
2399  *	A UI or UIH frame has arrived which contains data for a channel
2400  *	other than the control channel. If the relevant virtual tty is
2401  *	open we shovel the bits down it, if not we drop them.
2402  */
2403 
2404 static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
2405 {
2406 	/* krefs .. */
2407 	struct tty_port *port = &dlci->port;
2408 	struct tty_struct *tty;
2409 	unsigned int modem = 0;
2410 	int len;
2411 
2412 	if (debug & DBG_TTY)
2413 		pr_debug("%d bytes for tty\n", clen);
2414 	switch (dlci->adaption)  {
2415 	/* Unsupported types */
2416 	case 4:		/* Packetised interruptible data */
2417 		break;
2418 	case 3:		/* Packetised uininterruptible voice/data */
2419 		break;
2420 	case 2:		/* Asynchronous serial with line state in each frame */
2421 		len = gsm_read_ea_val(&modem, data, clen);
2422 		if (len < 1)
2423 			return;
2424 		tty = tty_port_tty_get(port);
2425 		if (tty) {
2426 			gsm_process_modem(tty, dlci, modem, len);
2427 			tty_wakeup(tty);
2428 			tty_kref_put(tty);
2429 		}
2430 		/* Skip processed modem data */
2431 		data += len;
2432 		clen -= len;
2433 		fallthrough;
2434 	case 1:		/* Line state will go via DLCI 0 controls only */
2435 	default:
2436 		tty_insert_flip_string(port, data, clen);
2437 		tty_flip_buffer_push(port);
2438 	}
2439 }
2440 
2441 /**
2442  *	gsm_dlci_command	-	data arrived on control channel
2443  *	@dlci: channel
2444  *	@data: block of bytes received
2445  *	@len: length of received block
2446  *
2447  *	A UI or UIH frame has arrived which contains data for DLCI 0 the
2448  *	control channel. This should contain a command EA followed by
2449  *	control data bytes. The command EA contains a command/response bit
2450  *	and we divide up the work accordingly.
2451  */
2452 
2453 static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
2454 {
2455 	/* See what command is involved */
2456 	unsigned int command = 0;
2457 	unsigned int clen = 0;
2458 	unsigned int dlen;
2459 
2460 	/* read the command */
2461 	dlen = gsm_read_ea_val(&command, data, len);
2462 	len -= dlen;
2463 	data += dlen;
2464 
2465 	/* read any control data */
2466 	dlen = gsm_read_ea_val(&clen, data, len);
2467 	len -= dlen;
2468 	data += dlen;
2469 
2470 	/* Malformed command? */
2471 	if (clen > len) {
2472 		dlci->gsm->malformed++;
2473 		return;
2474 	}
2475 
2476 	if (command & 1)
2477 		gsm_control_message(dlci->gsm, command, data, clen);
2478 	else
2479 		gsm_control_response(dlci->gsm, command, data, clen);
2480 }
2481 
2482 /**
2483  *	gsm_kick_timer	-	transmit if possible
2484  *	@t: timer contained in our gsm object
2485  *
2486  *	Transmit data from DLCIs if the queue is empty. We can't rely on
2487  *	a tty wakeup except when we filled the pipe so we need to fire off
2488  *	new data ourselves in other cases.
2489  */
2490 static void gsm_kick_timer(struct timer_list *t)
2491 {
2492 	struct gsm_mux *gsm = from_timer(gsm, t, kick_timer);
2493 	unsigned long flags;
2494 	int sent = 0;
2495 
2496 	spin_lock_irqsave(&gsm->tx_lock, flags);
2497 	/* If we have nothing running then we need to fire up */
2498 	if (gsm->tx_bytes < TX_THRESH_LO)
2499 		sent = gsm_dlci_data_sweep(gsm);
2500 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
2501 
2502 	if (sent && debug & DBG_DATA)
2503 		pr_info("%s TX queue stalled\n", __func__);
2504 }
2505 
2506 /**
2507  * gsm_dlci_copy_config_values	-	copy DLCI configuration
2508  * @dlci: source DLCI
2509  * @dc: configuration structure to fill
2510  */
2511 static void gsm_dlci_copy_config_values(struct gsm_dlci *dlci, struct gsm_dlci_config *dc)
2512 {
2513 	memset(dc, 0, sizeof(*dc));
2514 	dc->channel = (u32)dlci->addr;
2515 	dc->adaption = (u32)dlci->adaption;
2516 	dc->mtu = (u32)dlci->mtu;
2517 	dc->priority = (u32)dlci->prio;
2518 	if (dlci->ftype == UIH)
2519 		dc->i = 1;
2520 	else
2521 		dc->i = 2;
2522 	dc->k = (u32)dlci->k;
2523 }
2524 
2525 /**
2526  * gsm_dlci_config	-	configure DLCI from configuration
2527  * @dlci: DLCI to configure
2528  * @dc: DLCI configuration
2529  * @open: open DLCI after configuration?
2530  */
2531 static int gsm_dlci_config(struct gsm_dlci *dlci, struct gsm_dlci_config *dc, int open)
2532 {
2533 	struct gsm_mux *gsm;
2534 	bool need_restart = false;
2535 	bool need_open = false;
2536 	unsigned int i;
2537 
2538 	/*
2539 	 * Check that userspace doesn't put stuff in here to prevent breakages
2540 	 * in the future.
2541 	 */
2542 	for (i = 0; i < ARRAY_SIZE(dc->reserved); i++)
2543 		if (dc->reserved[i])
2544 			return -EINVAL;
2545 
2546 	if (!dlci)
2547 		return -EINVAL;
2548 	gsm = dlci->gsm;
2549 
2550 	/* Stuff we don't support yet - I frame transport */
2551 	if (dc->adaption != 1 && dc->adaption != 2)
2552 		return -EOPNOTSUPP;
2553 	if (dc->mtu > MAX_MTU || dc->mtu < MIN_MTU || dc->mtu > gsm->mru)
2554 		return -EINVAL;
2555 	if (dc->priority >= 64)
2556 		return -EINVAL;
2557 	if (dc->i == 0 || dc->i > 2)  /* UIH and UI only */
2558 		return -EINVAL;
2559 	if (dc->k > 7)
2560 		return -EINVAL;
2561 	if (dc->flags & ~GSM_FL_RESTART)   /* allow future extensions */
2562 		return -EINVAL;
2563 
2564 	/*
2565 	 * See what is needed for reconfiguration
2566 	 */
2567 	/* Framing fields */
2568 	if (dc->adaption != dlci->adaption)
2569 		need_restart = true;
2570 	if (dc->mtu != dlci->mtu)
2571 		need_restart = true;
2572 	if (dc->i != dlci->ftype)
2573 		need_restart = true;
2574 	/* Requires care */
2575 	if (dc->priority != dlci->prio)
2576 		need_restart = true;
2577 	if (dc->flags & GSM_FL_RESTART)
2578 		need_restart = true;
2579 
2580 	if ((open && gsm->wait_config) || need_restart)
2581 		need_open = true;
2582 	if (dlci->state == DLCI_WAITING_CONFIG) {
2583 		need_restart = false;
2584 		need_open = true;
2585 	}
2586 
2587 	/*
2588 	 * Close down what is needed, restart and initiate the new
2589 	 * configuration.
2590 	 */
2591 	if (need_restart) {
2592 		gsm_dlci_begin_close(dlci);
2593 		wait_event_interruptible(gsm->event, dlci->state == DLCI_CLOSED);
2594 		if (signal_pending(current))
2595 			return -EINTR;
2596 	}
2597 	/*
2598 	 * Setup the new configuration values
2599 	 */
2600 	dlci->adaption = (int)dc->adaption;
2601 
2602 	if (dc->mtu)
2603 		dlci->mtu = (unsigned int)dc->mtu;
2604 	else
2605 		dlci->mtu = gsm->mtu;
2606 
2607 	if (dc->priority)
2608 		dlci->prio = (u8)dc->priority;
2609 	else
2610 		dlci->prio = roundup(dlci->addr + 1, 8) - 1;
2611 
2612 	if (dc->i == 1)
2613 		dlci->ftype = UIH;
2614 	else if (dc->i == 2)
2615 		dlci->ftype = UI;
2616 
2617 	if (dc->k)
2618 		dlci->k = (u8)dc->k;
2619 	else
2620 		dlci->k = gsm->k;
2621 
2622 	if (need_open) {
2623 		if (gsm->initiator)
2624 			gsm_dlci_begin_open(dlci);
2625 		else
2626 			gsm_dlci_set_opening(dlci);
2627 	}
2628 
2629 	return 0;
2630 }
2631 
2632 /*
2633  *	Allocate/Free DLCI channels
2634  */
2635 
2636 /**
2637  *	gsm_dlci_alloc		-	allocate a DLCI
2638  *	@gsm: GSM mux
2639  *	@addr: address of the DLCI
2640  *
2641  *	Allocate and install a new DLCI object into the GSM mux.
2642  *
2643  *	FIXME: review locking races
2644  */
2645 
2646 static struct gsm_dlci *gsm_dlci_alloc(struct gsm_mux *gsm, int addr)
2647 {
2648 	struct gsm_dlci *dlci = kzalloc(sizeof(struct gsm_dlci), GFP_ATOMIC);
2649 	if (dlci == NULL)
2650 		return NULL;
2651 	spin_lock_init(&dlci->lock);
2652 	mutex_init(&dlci->mutex);
2653 	if (kfifo_alloc(&dlci->fifo, TX_SIZE, GFP_KERNEL) < 0) {
2654 		kfree(dlci);
2655 		return NULL;
2656 	}
2657 
2658 	skb_queue_head_init(&dlci->skb_list);
2659 	timer_setup(&dlci->t1, gsm_dlci_t1, 0);
2660 	tty_port_init(&dlci->port);
2661 	dlci->port.ops = &gsm_port_ops;
2662 	dlci->gsm = gsm;
2663 	dlci->addr = addr;
2664 	dlci->adaption = gsm->adaption;
2665 	dlci->mtu = gsm->mtu;
2666 	if (addr == 0)
2667 		dlci->prio = 0;
2668 	else
2669 		dlci->prio = roundup(addr + 1, 8) - 1;
2670 	dlci->ftype = gsm->ftype;
2671 	dlci->k = gsm->k;
2672 	dlci->state = DLCI_CLOSED;
2673 	if (addr) {
2674 		dlci->data = gsm_dlci_data;
2675 		/* Prevent us from sending data before the link is up */
2676 		dlci->constipated = true;
2677 	} else {
2678 		dlci->data = gsm_dlci_command;
2679 	}
2680 	gsm->dlci[addr] = dlci;
2681 	return dlci;
2682 }
2683 
2684 /**
2685  *	gsm_dlci_free		-	free DLCI
2686  *	@port: tty port for DLCI to free
2687  *
2688  *	Free up a DLCI.
2689  *
2690  *	Can sleep.
2691  */
2692 static void gsm_dlci_free(struct tty_port *port)
2693 {
2694 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
2695 
2696 	timer_shutdown_sync(&dlci->t1);
2697 	dlci->gsm->dlci[dlci->addr] = NULL;
2698 	kfifo_free(&dlci->fifo);
2699 	while ((dlci->skb = skb_dequeue(&dlci->skb_list)))
2700 		dev_kfree_skb(dlci->skb);
2701 	kfree(dlci);
2702 }
2703 
2704 static inline void dlci_get(struct gsm_dlci *dlci)
2705 {
2706 	tty_port_get(&dlci->port);
2707 }
2708 
2709 static inline void dlci_put(struct gsm_dlci *dlci)
2710 {
2711 	tty_port_put(&dlci->port);
2712 }
2713 
2714 static void gsm_destroy_network(struct gsm_dlci *dlci);
2715 
2716 /**
2717  *	gsm_dlci_release		-	release DLCI
2718  *	@dlci: DLCI to destroy
2719  *
2720  *	Release a DLCI. Actual free is deferred until either
2721  *	mux is closed or tty is closed - whichever is last.
2722  *
2723  *	Can sleep.
2724  */
2725 static void gsm_dlci_release(struct gsm_dlci *dlci)
2726 {
2727 	struct tty_struct *tty = tty_port_tty_get(&dlci->port);
2728 	if (tty) {
2729 		mutex_lock(&dlci->mutex);
2730 		gsm_destroy_network(dlci);
2731 		mutex_unlock(&dlci->mutex);
2732 
2733 		/* We cannot use tty_hangup() because in tty_kref_put() the tty
2734 		 * driver assumes that the hangup queue is free and reuses it to
2735 		 * queue release_one_tty() -> NULL pointer panic in
2736 		 * process_one_work().
2737 		 */
2738 		tty_vhangup(tty);
2739 
2740 		tty_port_tty_set(&dlci->port, NULL);
2741 		tty_kref_put(tty);
2742 	}
2743 	dlci->state = DLCI_CLOSED;
2744 	dlci_put(dlci);
2745 }
2746 
2747 /*
2748  *	LAPBish link layer logic
2749  */
2750 
2751 /**
2752  *	gsm_queue		-	a GSM frame is ready to process
2753  *	@gsm: pointer to our gsm mux
2754  *
2755  *	At this point in time a frame has arrived and been demangled from
2756  *	the line encoding. All the differences between the encodings have
2757  *	been handled below us and the frame is unpacked into the structures.
2758  *	The fcs holds the header FCS but any data FCS must be added here.
2759  */
2760 
2761 static void gsm_queue(struct gsm_mux *gsm)
2762 {
2763 	struct gsm_dlci *dlci;
2764 	u8 cr;
2765 	int address;
2766 
2767 	if (gsm->fcs != GOOD_FCS) {
2768 		gsm->bad_fcs++;
2769 		if (debug & DBG_DATA)
2770 			pr_debug("BAD FCS %02x\n", gsm->fcs);
2771 		return;
2772 	}
2773 	address = gsm->address >> 1;
2774 	if (address >= NUM_DLCI)
2775 		goto invalid;
2776 
2777 	cr = gsm->address & 1;		/* C/R bit */
2778 	cr ^= gsm->initiator ? 0 : 1;	/* Flip so 1 always means command */
2779 
2780 	gsm_print_packet("<--", address, cr, gsm->control, gsm->buf, gsm->len);
2781 
2782 	dlci = gsm->dlci[address];
2783 
2784 	switch (gsm->control) {
2785 	case SABM|PF:
2786 		if (cr == 1) {
2787 			gsm->open_error++;
2788 			goto invalid;
2789 		}
2790 		if (dlci == NULL)
2791 			dlci = gsm_dlci_alloc(gsm, address);
2792 		if (dlci == NULL) {
2793 			gsm->open_error++;
2794 			return;
2795 		}
2796 		if (dlci->dead)
2797 			gsm_response(gsm, address, DM|PF);
2798 		else {
2799 			gsm_response(gsm, address, UA|PF);
2800 			gsm_dlci_open(dlci);
2801 		}
2802 		break;
2803 	case DISC|PF:
2804 		if (cr == 1)
2805 			goto invalid;
2806 		if (dlci == NULL || dlci->state == DLCI_CLOSED) {
2807 			gsm_response(gsm, address, DM|PF);
2808 			return;
2809 		}
2810 		/* Real close complete */
2811 		gsm_response(gsm, address, UA|PF);
2812 		gsm_dlci_close(dlci);
2813 		break;
2814 	case UA|PF:
2815 		if (cr == 0 || dlci == NULL)
2816 			break;
2817 		switch (dlci->state) {
2818 		case DLCI_CLOSING:
2819 			gsm_dlci_close(dlci);
2820 			break;
2821 		case DLCI_OPENING:
2822 			gsm_dlci_open(dlci);
2823 			break;
2824 		default:
2825 			pr_debug("%s: unhandled state: %d\n", __func__,
2826 					dlci->state);
2827 			break;
2828 		}
2829 		break;
2830 	case DM:	/* DM can be valid unsolicited */
2831 	case DM|PF:
2832 		if (cr)
2833 			goto invalid;
2834 		if (dlci == NULL)
2835 			return;
2836 		gsm_dlci_close(dlci);
2837 		break;
2838 	case UI:
2839 	case UI|PF:
2840 	case UIH:
2841 	case UIH|PF:
2842 		if (dlci == NULL || dlci->state != DLCI_OPEN) {
2843 			gsm_response(gsm, address, DM|PF);
2844 			return;
2845 		}
2846 		dlci->data(dlci, gsm->buf, gsm->len);
2847 		break;
2848 	default:
2849 		goto invalid;
2850 	}
2851 	return;
2852 invalid:
2853 	gsm->malformed++;
2854 	return;
2855 }
2856 
2857 /**
2858  * gsm0_receive_state_check_and_fix	-	check and correct receive state
2859  * @gsm: gsm data for this ldisc instance
2860  *
2861  * Ensures that the current receive state is valid for basic option mode.
2862  */
2863 
2864 static void gsm0_receive_state_check_and_fix(struct gsm_mux *gsm)
2865 {
2866 	switch (gsm->state) {
2867 	case GSM_SEARCH:
2868 	case GSM0_ADDRESS:
2869 	case GSM0_CONTROL:
2870 	case GSM0_LEN0:
2871 	case GSM0_LEN1:
2872 	case GSM0_DATA:
2873 	case GSM0_FCS:
2874 	case GSM0_SSOF:
2875 		break;
2876 	default:
2877 		gsm->state = GSM_SEARCH;
2878 		break;
2879 	}
2880 }
2881 
2882 /**
2883  *	gsm0_receive	-	perform processing for non-transparency
2884  *	@gsm: gsm data for this ldisc instance
2885  *	@c: character
2886  *
2887  *	Receive bytes in gsm mode 0
2888  */
2889 
2890 static void gsm0_receive(struct gsm_mux *gsm, u8 c)
2891 {
2892 	unsigned int len;
2893 
2894 	gsm0_receive_state_check_and_fix(gsm);
2895 	switch (gsm->state) {
2896 	case GSM_SEARCH:	/* SOF marker */
2897 		if (c == GSM0_SOF) {
2898 			gsm->state = GSM0_ADDRESS;
2899 			gsm->address = 0;
2900 			gsm->len = 0;
2901 			gsm->fcs = INIT_FCS;
2902 		}
2903 		break;
2904 	case GSM0_ADDRESS:	/* Address EA */
2905 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2906 		if (gsm_read_ea(&gsm->address, c))
2907 			gsm->state = GSM0_CONTROL;
2908 		break;
2909 	case GSM0_CONTROL:	/* Control Byte */
2910 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2911 		gsm->control = c;
2912 		gsm->state = GSM0_LEN0;
2913 		break;
2914 	case GSM0_LEN0:		/* Length EA */
2915 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2916 		if (gsm_read_ea(&gsm->len, c)) {
2917 			if (gsm->len > gsm->mru) {
2918 				gsm->bad_size++;
2919 				gsm->state = GSM_SEARCH;
2920 				break;
2921 			}
2922 			gsm->count = 0;
2923 			if (!gsm->len)
2924 				gsm->state = GSM0_FCS;
2925 			else
2926 				gsm->state = GSM0_DATA;
2927 			break;
2928 		}
2929 		gsm->state = GSM0_LEN1;
2930 		break;
2931 	case GSM0_LEN1:
2932 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2933 		len = c;
2934 		gsm->len |= len << 7;
2935 		if (gsm->len > gsm->mru) {
2936 			gsm->bad_size++;
2937 			gsm->state = GSM_SEARCH;
2938 			break;
2939 		}
2940 		gsm->count = 0;
2941 		if (!gsm->len)
2942 			gsm->state = GSM0_FCS;
2943 		else
2944 			gsm->state = GSM0_DATA;
2945 		break;
2946 	case GSM0_DATA:		/* Data */
2947 		gsm->buf[gsm->count++] = c;
2948 		if (gsm->count >= MAX_MRU) {
2949 			gsm->bad_size++;
2950 			gsm->state = GSM_SEARCH;
2951 		} else if (gsm->count >= gsm->len) {
2952 			/* Calculate final FCS for UI frames over all data */
2953 			if ((gsm->control & ~PF) != UIH) {
2954 				gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf,
2955 							     gsm->count);
2956 			}
2957 			gsm->state = GSM0_FCS;
2958 		}
2959 		break;
2960 	case GSM0_FCS:		/* FCS follows the packet */
2961 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2962 		gsm->state = GSM0_SSOF;
2963 		break;
2964 	case GSM0_SSOF:
2965 		gsm->state = GSM_SEARCH;
2966 		if (c == GSM0_SOF)
2967 			gsm_queue(gsm);
2968 		else
2969 			gsm->bad_size++;
2970 		break;
2971 	default:
2972 		pr_debug("%s: unhandled state: %d\n", __func__, gsm->state);
2973 		break;
2974 	}
2975 }
2976 
2977 /**
2978  * gsm1_receive_state_check_and_fix	-	check and correct receive state
2979  * @gsm: gsm data for this ldisc instance
2980  *
2981  * Ensures that the current receive state is valid for advanced option mode.
2982  */
2983 
2984 static void gsm1_receive_state_check_and_fix(struct gsm_mux *gsm)
2985 {
2986 	switch (gsm->state) {
2987 	case GSM_SEARCH:
2988 	case GSM1_START:
2989 	case GSM1_ADDRESS:
2990 	case GSM1_CONTROL:
2991 	case GSM1_DATA:
2992 	case GSM1_OVERRUN:
2993 		break;
2994 	default:
2995 		gsm->state = GSM_SEARCH;
2996 		break;
2997 	}
2998 }
2999 
3000 /**
3001  *	gsm1_receive	-	perform processing for non-transparency
3002  *	@gsm: gsm data for this ldisc instance
3003  *	@c: character
3004  *
3005  *	Receive bytes in mode 1 (Advanced option)
3006  */
3007 
3008 static void gsm1_receive(struct gsm_mux *gsm, u8 c)
3009 {
3010 	gsm1_receive_state_check_and_fix(gsm);
3011 	/* handle XON/XOFF */
3012 	if ((c & ISO_IEC_646_MASK) == XON) {
3013 		gsm->constipated = true;
3014 		return;
3015 	} else if ((c & ISO_IEC_646_MASK) == XOFF) {
3016 		gsm->constipated = false;
3017 		/* Kick the link in case it is idling */
3018 		gsmld_write_trigger(gsm);
3019 		return;
3020 	}
3021 	if (c == GSM1_SOF) {
3022 		/* EOF is only valid in frame if we have got to the data state */
3023 		if (gsm->state == GSM1_DATA) {
3024 			if (gsm->count < 1) {
3025 				/* Missing FSC */
3026 				gsm->malformed++;
3027 				gsm->state = GSM1_START;
3028 				return;
3029 			}
3030 			/* Remove the FCS from data */
3031 			gsm->count--;
3032 			if ((gsm->control & ~PF) != UIH) {
3033 				/* Calculate final FCS for UI frames over all
3034 				 * data but FCS
3035 				 */
3036 				gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf,
3037 							     gsm->count);
3038 			}
3039 			/* Add the FCS itself to test against GOOD_FCS */
3040 			gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->buf[gsm->count]);
3041 			gsm->len = gsm->count;
3042 			gsm_queue(gsm);
3043 			gsm->state  = GSM1_START;
3044 			return;
3045 		}
3046 		/* Any partial frame was a runt so go back to start */
3047 		if (gsm->state != GSM1_START) {
3048 			if (gsm->state != GSM_SEARCH)
3049 				gsm->malformed++;
3050 			gsm->state = GSM1_START;
3051 		}
3052 		/* A SOF in GSM_START means we are still reading idling or
3053 		   framing bytes */
3054 		return;
3055 	}
3056 
3057 	if (c == GSM1_ESCAPE) {
3058 		gsm->escape = true;
3059 		return;
3060 	}
3061 
3062 	/* Only an unescaped SOF gets us out of GSM search */
3063 	if (gsm->state == GSM_SEARCH)
3064 		return;
3065 
3066 	if (gsm->escape) {
3067 		c ^= GSM1_ESCAPE_BITS;
3068 		gsm->escape = false;
3069 	}
3070 	switch (gsm->state) {
3071 	case GSM1_START:		/* First byte after SOF */
3072 		gsm->address = 0;
3073 		gsm->state = GSM1_ADDRESS;
3074 		gsm->fcs = INIT_FCS;
3075 		fallthrough;
3076 	case GSM1_ADDRESS:	/* Address continuation */
3077 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
3078 		if (gsm_read_ea(&gsm->address, c))
3079 			gsm->state = GSM1_CONTROL;
3080 		break;
3081 	case GSM1_CONTROL:	/* Control Byte */
3082 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
3083 		gsm->control = c;
3084 		gsm->count = 0;
3085 		gsm->state = GSM1_DATA;
3086 		break;
3087 	case GSM1_DATA:		/* Data */
3088 		if (gsm->count > gsm->mru || gsm->count > MAX_MRU) {	/* Allow one for the FCS */
3089 			gsm->state = GSM1_OVERRUN;
3090 			gsm->bad_size++;
3091 		} else
3092 			gsm->buf[gsm->count++] = c;
3093 		break;
3094 	case GSM1_OVERRUN:	/* Over-long - eg a dropped SOF */
3095 		break;
3096 	default:
3097 		pr_debug("%s: unhandled state: %d\n", __func__, gsm->state);
3098 		break;
3099 	}
3100 }
3101 
3102 /**
3103  *	gsm_error		-	handle tty error
3104  *	@gsm: ldisc data
3105  *
3106  *	Handle an error in the receipt of data for a frame. Currently we just
3107  *	go back to hunting for a SOF.
3108  *
3109  *	FIXME: better diagnostics ?
3110  */
3111 
3112 static void gsm_error(struct gsm_mux *gsm)
3113 {
3114 	gsm->state = GSM_SEARCH;
3115 	gsm->io_error++;
3116 }
3117 
3118 /**
3119  *	gsm_cleanup_mux		-	generic GSM protocol cleanup
3120  *	@gsm: our mux
3121  *	@disc: disconnect link?
3122  *
3123  *	Clean up the bits of the mux which are the same for all framing
3124  *	protocols. Remove the mux from the mux table, stop all the timers
3125  *	and then shut down each device hanging up the channels as we go.
3126  */
3127 
3128 static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
3129 {
3130 	int i;
3131 	struct gsm_dlci *dlci;
3132 	struct gsm_msg *txq, *ntxq;
3133 
3134 	gsm->dead = true;
3135 	mutex_lock(&gsm->mutex);
3136 
3137 	dlci = gsm->dlci[0];
3138 	if (dlci) {
3139 		if (disc && dlci->state != DLCI_CLOSED) {
3140 			gsm_dlci_begin_close(dlci);
3141 			wait_event(gsm->event, dlci->state == DLCI_CLOSED);
3142 		}
3143 		dlci->dead = true;
3144 	}
3145 
3146 	/* Finish outstanding timers, making sure they are done */
3147 	del_timer_sync(&gsm->kick_timer);
3148 	del_timer_sync(&gsm->t2_timer);
3149 	del_timer_sync(&gsm->ka_timer);
3150 
3151 	/* Finish writing to ldisc */
3152 	flush_work(&gsm->tx_work);
3153 
3154 	/* Free up any link layer users and finally the control channel */
3155 	if (gsm->has_devices) {
3156 		gsm_unregister_devices(gsm_tty_driver, gsm->num);
3157 		gsm->has_devices = false;
3158 	}
3159 	for (i = NUM_DLCI - 1; i >= 0; i--)
3160 		if (gsm->dlci[i])
3161 			gsm_dlci_release(gsm->dlci[i]);
3162 	mutex_unlock(&gsm->mutex);
3163 	/* Now wipe the queues */
3164 	tty_ldisc_flush(gsm->tty);
3165 
3166 	guard(spinlock_irqsave)(&gsm->tx_lock);
3167 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_ctrl_list, list)
3168 		kfree(txq);
3169 	INIT_LIST_HEAD(&gsm->tx_ctrl_list);
3170 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_data_list, list)
3171 		kfree(txq);
3172 	INIT_LIST_HEAD(&gsm->tx_data_list);
3173 }
3174 
3175 /**
3176  *	gsm_activate_mux	-	generic GSM setup
3177  *	@gsm: our mux
3178  *
3179  *	Set up the bits of the mux which are the same for all framing
3180  *	protocols. Add the mux to the mux table so it can be opened and
3181  *	finally kick off connecting to DLCI 0 on the modem.
3182  */
3183 
3184 static int gsm_activate_mux(struct gsm_mux *gsm)
3185 {
3186 	struct gsm_dlci *dlci;
3187 	int ret;
3188 
3189 	dlci = gsm_dlci_alloc(gsm, 0);
3190 	if (dlci == NULL)
3191 		return -ENOMEM;
3192 
3193 	if (gsm->encoding == GSM_BASIC_OPT)
3194 		gsm->receive = gsm0_receive;
3195 	else
3196 		gsm->receive = gsm1_receive;
3197 
3198 	ret = gsm_register_devices(gsm_tty_driver, gsm->num);
3199 	if (ret)
3200 		return ret;
3201 
3202 	gsm->has_devices = true;
3203 	gsm->dead = false;		/* Tty opens are now permissible */
3204 	return 0;
3205 }
3206 
3207 /**
3208  *	gsm_free_mux		-	free up a mux
3209  *	@gsm: mux to free
3210  *
3211  *	Dispose of allocated resources for a dead mux
3212  */
3213 static void gsm_free_mux(struct gsm_mux *gsm)
3214 {
3215 	int i;
3216 
3217 	for (i = 0; i < MAX_MUX; i++) {
3218 		if (gsm == gsm_mux[i]) {
3219 			gsm_mux[i] = NULL;
3220 			break;
3221 		}
3222 	}
3223 	mutex_destroy(&gsm->mutex);
3224 	kfree(gsm->txframe);
3225 	kfree(gsm->buf);
3226 	kfree(gsm);
3227 }
3228 
3229 /**
3230  *	gsm_free_muxr		-	free up a mux
3231  *	@ref: kreference to the mux to free
3232  *
3233  *	Dispose of allocated resources for a dead mux
3234  */
3235 static void gsm_free_muxr(struct kref *ref)
3236 {
3237 	struct gsm_mux *gsm = container_of(ref, struct gsm_mux, ref);
3238 	gsm_free_mux(gsm);
3239 }
3240 
3241 static inline void mux_get(struct gsm_mux *gsm)
3242 {
3243 	unsigned long flags;
3244 
3245 	spin_lock_irqsave(&gsm_mux_lock, flags);
3246 	kref_get(&gsm->ref);
3247 	spin_unlock_irqrestore(&gsm_mux_lock, flags);
3248 }
3249 
3250 static inline void mux_put(struct gsm_mux *gsm)
3251 {
3252 	unsigned long flags;
3253 
3254 	spin_lock_irqsave(&gsm_mux_lock, flags);
3255 	kref_put(&gsm->ref, gsm_free_muxr);
3256 	spin_unlock_irqrestore(&gsm_mux_lock, flags);
3257 }
3258 
3259 static inline unsigned int mux_num_to_base(struct gsm_mux *gsm)
3260 {
3261 	return gsm->num * NUM_DLCI;
3262 }
3263 
3264 static inline unsigned int mux_line_to_num(unsigned int line)
3265 {
3266 	return line / NUM_DLCI;
3267 }
3268 
3269 /**
3270  *	gsm_alloc_mux		-	allocate a mux
3271  *
3272  *	Creates a new mux ready for activation.
3273  */
3274 
3275 static struct gsm_mux *gsm_alloc_mux(void)
3276 {
3277 	int i;
3278 	struct gsm_mux *gsm = kzalloc(sizeof(struct gsm_mux), GFP_KERNEL);
3279 	if (gsm == NULL)
3280 		return NULL;
3281 	gsm->buf = kmalloc(MAX_MRU + 1, GFP_KERNEL);
3282 	if (gsm->buf == NULL) {
3283 		kfree(gsm);
3284 		return NULL;
3285 	}
3286 	gsm->txframe = kmalloc(2 * (MAX_MTU + PROT_OVERHEAD - 1), GFP_KERNEL);
3287 	if (gsm->txframe == NULL) {
3288 		kfree(gsm->buf);
3289 		kfree(gsm);
3290 		return NULL;
3291 	}
3292 	spin_lock_init(&gsm->lock);
3293 	mutex_init(&gsm->mutex);
3294 	kref_init(&gsm->ref);
3295 	INIT_LIST_HEAD(&gsm->tx_ctrl_list);
3296 	INIT_LIST_HEAD(&gsm->tx_data_list);
3297 	timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
3298 	timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
3299 	timer_setup(&gsm->ka_timer, gsm_control_keep_alive, 0);
3300 	INIT_WORK(&gsm->tx_work, gsmld_write_task);
3301 	init_waitqueue_head(&gsm->event);
3302 	spin_lock_init(&gsm->control_lock);
3303 	spin_lock_init(&gsm->tx_lock);
3304 
3305 	gsm->t1 = T1;
3306 	gsm->t2 = T2;
3307 	gsm->t3 = T3;
3308 	gsm->n2 = N2;
3309 	gsm->k = K;
3310 	gsm->ftype = UIH;
3311 	gsm->adaption = 1;
3312 	gsm->encoding = GSM_ADV_OPT;
3313 	gsm->mru = 64;	/* Default to encoding 1 so these should be 64 */
3314 	gsm->mtu = 64;
3315 	gsm->dead = true;	/* Avoid early tty opens */
3316 	gsm->wait_config = false; /* Disabled */
3317 	gsm->keep_alive = 0;	/* Disabled */
3318 
3319 	/* Store the instance to the mux array or abort if no space is
3320 	 * available.
3321 	 */
3322 	spin_lock(&gsm_mux_lock);
3323 	for (i = 0; i < MAX_MUX; i++) {
3324 		if (!gsm_mux[i]) {
3325 			gsm_mux[i] = gsm;
3326 			gsm->num = i;
3327 			break;
3328 		}
3329 	}
3330 	spin_unlock(&gsm_mux_lock);
3331 	if (i == MAX_MUX) {
3332 		mutex_destroy(&gsm->mutex);
3333 		kfree(gsm->txframe);
3334 		kfree(gsm->buf);
3335 		kfree(gsm);
3336 		return NULL;
3337 	}
3338 
3339 	return gsm;
3340 }
3341 
3342 static void gsm_copy_config_values(struct gsm_mux *gsm,
3343 				   struct gsm_config *c)
3344 {
3345 	memset(c, 0, sizeof(*c));
3346 	c->adaption = gsm->adaption;
3347 	c->encapsulation = gsm->encoding;
3348 	c->initiator = gsm->initiator;
3349 	c->t1 = gsm->t1;
3350 	c->t2 = gsm->t2;
3351 	c->t3 = gsm->t3;
3352 	c->n2 = gsm->n2;
3353 	if (gsm->ftype == UIH)
3354 		c->i = 1;
3355 	else
3356 		c->i = 2;
3357 	pr_debug("Ftype %d i %d\n", gsm->ftype, c->i);
3358 	c->mru = gsm->mru;
3359 	c->mtu = gsm->mtu;
3360 	c->k = gsm->k;
3361 }
3362 
3363 static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
3364 {
3365 	int need_close = 0;
3366 	int need_restart = 0;
3367 
3368 	/* Stuff we don't support yet - UI or I frame transport */
3369 	if (c->adaption != 1 && c->adaption != 2)
3370 		return -EOPNOTSUPP;
3371 	/* Check the MRU/MTU range looks sane */
3372 	if (c->mru < MIN_MTU || c->mtu < MIN_MTU)
3373 		return -EINVAL;
3374 	if (c->mru > MAX_MRU || c->mtu > MAX_MTU)
3375 		return -EINVAL;
3376 	if (c->t3 > MAX_T3)
3377 		return -EINVAL;
3378 	if (c->n2 > 255)
3379 		return -EINVAL;
3380 	if (c->encapsulation > 1)	/* Basic, advanced, no I */
3381 		return -EINVAL;
3382 	if (c->initiator > 1)
3383 		return -EINVAL;
3384 	if (c->k > MAX_WINDOW_SIZE)
3385 		return -EINVAL;
3386 	if (c->i == 0 || c->i > 2)	/* UIH and UI only */
3387 		return -EINVAL;
3388 	/*
3389 	 * See what is needed for reconfiguration
3390 	 */
3391 
3392 	/* Timing fields */
3393 	if (c->t1 != 0 && c->t1 != gsm->t1)
3394 		need_restart = 1;
3395 	if (c->t2 != 0 && c->t2 != gsm->t2)
3396 		need_restart = 1;
3397 	if (c->encapsulation != gsm->encoding)
3398 		need_restart = 1;
3399 	if (c->adaption != gsm->adaption)
3400 		need_restart = 1;
3401 	/* Requires care */
3402 	if (c->initiator != gsm->initiator)
3403 		need_close = 1;
3404 	if (c->mru != gsm->mru)
3405 		need_restart = 1;
3406 	if (c->mtu != gsm->mtu)
3407 		need_restart = 1;
3408 
3409 	/*
3410 	 * Close down what is needed, restart and initiate the new
3411 	 * configuration. On the first time there is no DLCI[0]
3412 	 * and closing or cleaning up is not necessary.
3413 	 */
3414 	if (need_close || need_restart)
3415 		gsm_cleanup_mux(gsm, true);
3416 
3417 	gsm->initiator = c->initiator;
3418 	gsm->mru = c->mru;
3419 	gsm->mtu = c->mtu;
3420 	gsm->encoding = c->encapsulation ? GSM_ADV_OPT : GSM_BASIC_OPT;
3421 	gsm->adaption = c->adaption;
3422 	gsm->n2 = c->n2;
3423 
3424 	if (c->i == 1)
3425 		gsm->ftype = UIH;
3426 	else if (c->i == 2)
3427 		gsm->ftype = UI;
3428 
3429 	if (c->t1)
3430 		gsm->t1 = c->t1;
3431 	if (c->t2)
3432 		gsm->t2 = c->t2;
3433 	if (c->t3)
3434 		gsm->t3 = c->t3;
3435 	if (c->k)
3436 		gsm->k = c->k;
3437 
3438 	/*
3439 	 * FIXME: We need to separate activation/deactivation from adding
3440 	 * and removing from the mux array
3441 	 */
3442 	if (gsm->dead) {
3443 		int ret = gsm_activate_mux(gsm);
3444 		if (ret)
3445 			return ret;
3446 		if (gsm->initiator)
3447 			gsm_dlci_begin_open(gsm->dlci[0]);
3448 	}
3449 	return 0;
3450 }
3451 
3452 static void gsm_copy_config_ext_values(struct gsm_mux *gsm,
3453 				       struct gsm_config_ext *ce)
3454 {
3455 	memset(ce, 0, sizeof(*ce));
3456 	ce->wait_config = gsm->wait_config ? 1 : 0;
3457 	ce->keep_alive = gsm->keep_alive;
3458 }
3459 
3460 static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)
3461 {
3462 	bool need_restart = false;
3463 	unsigned int i;
3464 
3465 	/*
3466 	 * Check that userspace doesn't put stuff in here to prevent breakages
3467 	 * in the future.
3468 	 */
3469 	for (i = 0; i < ARRAY_SIZE(ce->reserved); i++)
3470 		if (ce->reserved[i])
3471 			return -EINVAL;
3472 	if (ce->flags & ~GSM_FL_RESTART)
3473 		return -EINVAL;
3474 
3475 	/* Requires care */
3476 	if (ce->flags & GSM_FL_RESTART)
3477 		need_restart = true;
3478 
3479 	/*
3480 	 * Close down what is needed, restart and initiate the new
3481 	 * configuration. On the first time there is no DLCI[0]
3482 	 * and closing or cleaning up is not necessary.
3483 	 */
3484 	if (need_restart)
3485 		gsm_cleanup_mux(gsm, true);
3486 
3487 	/*
3488 	 * Setup the new configuration values
3489 	 */
3490 	gsm->wait_config = ce->wait_config ? true : false;
3491 	gsm->keep_alive = ce->keep_alive;
3492 
3493 	if (gsm->dead) {
3494 		int ret = gsm_activate_mux(gsm);
3495 		if (ret)
3496 			return ret;
3497 		if (gsm->initiator)
3498 			gsm_dlci_begin_open(gsm->dlci[0]);
3499 	}
3500 
3501 	return 0;
3502 }
3503 
3504 /**
3505  *	gsmld_output		-	write to link
3506  *	@gsm: our mux
3507  *	@data: bytes to output
3508  *	@len: size
3509  *
3510  *	Write a block of data from the GSM mux to the data channel. This
3511  *	will eventually be serialized from above but at the moment isn't.
3512  */
3513 
3514 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
3515 {
3516 	if (tty_write_room(gsm->tty) < len) {
3517 		set_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
3518 		return -ENOSPC;
3519 	}
3520 	if (debug & DBG_DATA)
3521 		gsm_hex_dump_bytes(__func__, data, len);
3522 	return gsm->tty->ops->write(gsm->tty, data, len);
3523 }
3524 
3525 
3526 /**
3527  *	gsmld_write_trigger	-	schedule ldisc write task
3528  *	@gsm: our mux
3529  */
3530 static void gsmld_write_trigger(struct gsm_mux *gsm)
3531 {
3532 	if (!gsm || !gsm->dlci[0] || gsm->dlci[0]->dead)
3533 		return;
3534 	schedule_work(&gsm->tx_work);
3535 }
3536 
3537 
3538 /**
3539  *	gsmld_write_task	-	ldisc write task
3540  *	@work: our tx write work
3541  *
3542  *	Writes out data to the ldisc if possible. We are doing this here to
3543  *	avoid dead-locking. This returns if no space or data is left for output.
3544  */
3545 static void gsmld_write_task(struct work_struct *work)
3546 {
3547 	struct gsm_mux *gsm = container_of(work, struct gsm_mux, tx_work);
3548 	unsigned long flags;
3549 	int i, ret;
3550 
3551 	/* All outstanding control channel and control messages and one data
3552 	 * frame is sent.
3553 	 */
3554 	ret = -ENODEV;
3555 	spin_lock_irqsave(&gsm->tx_lock, flags);
3556 	if (gsm->tty)
3557 		ret = gsm_data_kick(gsm);
3558 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
3559 
3560 	if (ret >= 0)
3561 		for (i = 0; i < NUM_DLCI; i++)
3562 			if (gsm->dlci[i])
3563 				tty_port_tty_wakeup(&gsm->dlci[i]->port);
3564 }
3565 
3566 /**
3567  *	gsmld_attach_gsm	-	mode set up
3568  *	@tty: our tty structure
3569  *	@gsm: our mux
3570  *
3571  *	Set up the MUX for basic mode and commence connecting to the
3572  *	modem. Currently called from the line discipline set up but
3573  *	will need moving to an ioctl path.
3574  */
3575 
3576 static void gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
3577 {
3578 	gsm->tty = tty_kref_get(tty);
3579 	/* Turn off tty XON/XOFF handling to handle it explicitly. */
3580 	gsm->old_c_iflag = tty->termios.c_iflag;
3581 	tty->termios.c_iflag &= (IXON | IXOFF);
3582 }
3583 
3584 /**
3585  *	gsmld_detach_gsm	-	stop doing 0710 mux
3586  *	@tty: tty attached to the mux
3587  *	@gsm: mux
3588  *
3589  *	Shutdown and then clean up the resources used by the line discipline
3590  */
3591 
3592 static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
3593 {
3594 	WARN_ON(tty != gsm->tty);
3595 	/* Restore tty XON/XOFF handling. */
3596 	gsm->tty->termios.c_iflag = gsm->old_c_iflag;
3597 	tty_kref_put(gsm->tty);
3598 	gsm->tty = NULL;
3599 }
3600 
3601 static void gsmld_receive_buf(struct tty_struct *tty, const u8 *cp,
3602 			      const u8 *fp, size_t count)
3603 {
3604 	struct gsm_mux *gsm = tty->disc_data;
3605 	u8 flags = TTY_NORMAL;
3606 
3607 	if (debug & DBG_DATA)
3608 		gsm_hex_dump_bytes(__func__, cp, count);
3609 
3610 	for (; count; count--, cp++) {
3611 		if (fp)
3612 			flags = *fp++;
3613 		switch (flags) {
3614 		case TTY_NORMAL:
3615 			if (gsm->receive)
3616 				gsm->receive(gsm, *cp);
3617 			break;
3618 		case TTY_OVERRUN:
3619 		case TTY_BREAK:
3620 		case TTY_PARITY:
3621 		case TTY_FRAME:
3622 			gsm_error(gsm);
3623 			break;
3624 		default:
3625 			WARN_ONCE(1, "%s: unknown flag %d\n",
3626 			       tty_name(tty), flags);
3627 			break;
3628 		}
3629 	}
3630 	/* FASYNC if needed ? */
3631 	/* If clogged call tty_throttle(tty); */
3632 }
3633 
3634 /**
3635  *	gsmld_flush_buffer	-	clean input queue
3636  *	@tty:	terminal device
3637  *
3638  *	Flush the input buffer. Called when the line discipline is
3639  *	being closed, when the tty layer wants the buffer flushed (eg
3640  *	at hangup).
3641  */
3642 
3643 static void gsmld_flush_buffer(struct tty_struct *tty)
3644 {
3645 }
3646 
3647 /**
3648  *	gsmld_close		-	close the ldisc for this tty
3649  *	@tty: device
3650  *
3651  *	Called from the terminal layer when this line discipline is
3652  *	being shut down, either because of a close or becsuse of a
3653  *	discipline change. The function will not be called while other
3654  *	ldisc methods are in progress.
3655  */
3656 
3657 static void gsmld_close(struct tty_struct *tty)
3658 {
3659 	struct gsm_mux *gsm = tty->disc_data;
3660 
3661 	/* The ldisc locks and closes the port before calling our close. This
3662 	 * means we have no way to do a proper disconnect. We will not bother
3663 	 * to do one.
3664 	 */
3665 	gsm_cleanup_mux(gsm, false);
3666 
3667 	gsmld_detach_gsm(tty, gsm);
3668 
3669 	gsmld_flush_buffer(tty);
3670 	/* Do other clean up here */
3671 	mux_put(gsm);
3672 }
3673 
3674 /**
3675  *	gsmld_open		-	open an ldisc
3676  *	@tty: terminal to open
3677  *
3678  *	Called when this line discipline is being attached to the
3679  *	terminal device. Can sleep. Called serialized so that no
3680  *	other events will occur in parallel. No further open will occur
3681  *	until a close.
3682  */
3683 
3684 static int gsmld_open(struct tty_struct *tty)
3685 {
3686 	struct gsm_mux *gsm;
3687 
3688 	if (!capable(CAP_NET_ADMIN))
3689 		return -EPERM;
3690 
3691 	if (tty->ops->write == NULL)
3692 		return -EINVAL;
3693 
3694 	/* Attach our ldisc data */
3695 	gsm = gsm_alloc_mux();
3696 	if (gsm == NULL)
3697 		return -ENOMEM;
3698 
3699 	tty->disc_data = gsm;
3700 	tty->receive_room = 65536;
3701 
3702 	/* Attach the initial passive connection */
3703 	gsmld_attach_gsm(tty, gsm);
3704 
3705 	/* The mux will not be activated yet, we wait for correct
3706 	 * configuration first.
3707 	 */
3708 	if (gsm->encoding == GSM_BASIC_OPT)
3709 		gsm->receive = gsm0_receive;
3710 	else
3711 		gsm->receive = gsm1_receive;
3712 
3713 	return 0;
3714 }
3715 
3716 /**
3717  *	gsmld_write_wakeup	-	asynchronous I/O notifier
3718  *	@tty: tty device
3719  *
3720  *	Required for the ptys, serial driver etc. since processes
3721  *	that attach themselves to the master and rely on ASYNC
3722  *	IO must be woken up
3723  */
3724 
3725 static void gsmld_write_wakeup(struct tty_struct *tty)
3726 {
3727 	struct gsm_mux *gsm = tty->disc_data;
3728 
3729 	/* Queue poll */
3730 	gsmld_write_trigger(gsm);
3731 }
3732 
3733 /**
3734  *	gsmld_read		-	read function for tty
3735  *	@tty: tty device
3736  *	@file: file object
3737  *	@buf: userspace buffer pointer
3738  *	@nr: size of I/O
3739  *	@cookie: unused
3740  *	@offset: unused
3741  *
3742  *	Perform reads for the line discipline. We are guaranteed that the
3743  *	line discipline will not be closed under us but we may get multiple
3744  *	parallel readers and must handle this ourselves. We may also get
3745  *	a hangup. Always called in user context, may sleep.
3746  *
3747  *	This code must be sure never to sleep through a hangup.
3748  */
3749 
3750 static ssize_t gsmld_read(struct tty_struct *tty, struct file *file, u8 *buf,
3751 			  size_t nr, void **cookie, unsigned long offset)
3752 {
3753 	return -EOPNOTSUPP;
3754 }
3755 
3756 /**
3757  *	gsmld_write		-	write function for tty
3758  *	@tty: tty device
3759  *	@file: file object
3760  *	@buf: userspace buffer pointer
3761  *	@nr: size of I/O
3762  *
3763  *	Called when the owner of the device wants to send a frame
3764  *	itself (or some other control data). The data is transferred
3765  *	as-is and must be properly framed and checksummed as appropriate
3766  *	by userspace. Frames are either sent whole or not at all as this
3767  *	avoids pain user side.
3768  */
3769 
3770 static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
3771 			   const u8 *buf, size_t nr)
3772 {
3773 	struct gsm_mux *gsm = tty->disc_data;
3774 	unsigned long flags;
3775 	size_t space;
3776 	int ret;
3777 
3778 	if (!gsm)
3779 		return -ENODEV;
3780 
3781 	ret = -ENOBUFS;
3782 	spin_lock_irqsave(&gsm->tx_lock, flags);
3783 	space = tty_write_room(tty);
3784 	if (space >= nr)
3785 		ret = tty->ops->write(tty, buf, nr);
3786 	else
3787 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
3788 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
3789 
3790 	return ret;
3791 }
3792 
3793 /**
3794  *	gsmld_poll		-	poll method for N_GSM0710
3795  *	@tty: terminal device
3796  *	@file: file accessing it
3797  *	@wait: poll table
3798  *
3799  *	Called when the line discipline is asked to poll() for data or
3800  *	for special events. This code is not serialized with respect to
3801  *	other events save open/close.
3802  *
3803  *	This code must be sure never to sleep through a hangup.
3804  *	Called without the kernel lock held - fine
3805  */
3806 
3807 static __poll_t gsmld_poll(struct tty_struct *tty, struct file *file,
3808 							poll_table *wait)
3809 {
3810 	__poll_t mask = 0;
3811 	struct gsm_mux *gsm = tty->disc_data;
3812 
3813 	poll_wait(file, &tty->read_wait, wait);
3814 	poll_wait(file, &tty->write_wait, wait);
3815 
3816 	if (gsm->dead)
3817 		mask |= EPOLLHUP;
3818 	if (tty_hung_up_p(file))
3819 		mask |= EPOLLHUP;
3820 	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
3821 		mask |= EPOLLHUP;
3822 	if (!tty_is_writelocked(tty) && tty_write_room(tty) > 0)
3823 		mask |= EPOLLOUT | EPOLLWRNORM;
3824 	return mask;
3825 }
3826 
3827 static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
3828 		       unsigned long arg)
3829 {
3830 	struct gsm_config c;
3831 	struct gsm_config_ext ce;
3832 	struct gsm_dlci_config dc;
3833 	struct gsm_mux *gsm = tty->disc_data;
3834 	unsigned int base, addr;
3835 	struct gsm_dlci *dlci;
3836 
3837 	switch (cmd) {
3838 	case GSMIOC_GETCONF:
3839 		gsm_copy_config_values(gsm, &c);
3840 		if (copy_to_user((void __user *)arg, &c, sizeof(c)))
3841 			return -EFAULT;
3842 		return 0;
3843 	case GSMIOC_SETCONF:
3844 		if (copy_from_user(&c, (void __user *)arg, sizeof(c)))
3845 			return -EFAULT;
3846 		return gsm_config(gsm, &c);
3847 	case GSMIOC_GETFIRST:
3848 		base = mux_num_to_base(gsm);
3849 		return put_user(base + 1, (__u32 __user *)arg);
3850 	case GSMIOC_GETCONF_EXT:
3851 		gsm_copy_config_ext_values(gsm, &ce);
3852 		if (copy_to_user((void __user *)arg, &ce, sizeof(ce)))
3853 			return -EFAULT;
3854 		return 0;
3855 	case GSMIOC_SETCONF_EXT:
3856 		if (copy_from_user(&ce, (void __user *)arg, sizeof(ce)))
3857 			return -EFAULT;
3858 		return gsm_config_ext(gsm, &ce);
3859 	case GSMIOC_GETCONF_DLCI:
3860 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
3861 			return -EFAULT;
3862 		if (dc.channel == 0 || dc.channel >= NUM_DLCI)
3863 			return -EINVAL;
3864 		addr = array_index_nospec(dc.channel, NUM_DLCI);
3865 		dlci = gsm->dlci[addr];
3866 		if (!dlci) {
3867 			dlci = gsm_dlci_alloc(gsm, addr);
3868 			if (!dlci)
3869 				return -ENOMEM;
3870 		}
3871 		gsm_dlci_copy_config_values(dlci, &dc);
3872 		if (copy_to_user((void __user *)arg, &dc, sizeof(dc)))
3873 			return -EFAULT;
3874 		return 0;
3875 	case GSMIOC_SETCONF_DLCI:
3876 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
3877 			return -EFAULT;
3878 		if (dc.channel == 0 || dc.channel >= NUM_DLCI)
3879 			return -EINVAL;
3880 		addr = array_index_nospec(dc.channel, NUM_DLCI);
3881 		dlci = gsm->dlci[addr];
3882 		if (!dlci) {
3883 			dlci = gsm_dlci_alloc(gsm, addr);
3884 			if (!dlci)
3885 				return -ENOMEM;
3886 		}
3887 		return gsm_dlci_config(dlci, &dc, 0);
3888 	default:
3889 		return n_tty_ioctl_helper(tty, cmd, arg);
3890 	}
3891 }
3892 
3893 /*
3894  *	Network interface
3895  *
3896  */
3897 
3898 static int gsm_mux_net_open(struct net_device *net)
3899 {
3900 	pr_debug("%s called\n", __func__);
3901 	netif_start_queue(net);
3902 	return 0;
3903 }
3904 
3905 static int gsm_mux_net_close(struct net_device *net)
3906 {
3907 	netif_stop_queue(net);
3908 	return 0;
3909 }
3910 
3911 static void dlci_net_free(struct gsm_dlci *dlci)
3912 {
3913 	if (!dlci->net) {
3914 		WARN_ON(1);
3915 		return;
3916 	}
3917 	dlci->adaption = dlci->prev_adaption;
3918 	dlci->data = dlci->prev_data;
3919 	free_netdev(dlci->net);
3920 	dlci->net = NULL;
3921 }
3922 static void net_free(struct kref *ref)
3923 {
3924 	struct gsm_mux_net *mux_net;
3925 	struct gsm_dlci *dlci;
3926 
3927 	mux_net = container_of(ref, struct gsm_mux_net, ref);
3928 	dlci = mux_net->dlci;
3929 
3930 	if (dlci->net) {
3931 		unregister_netdev(dlci->net);
3932 		dlci_net_free(dlci);
3933 	}
3934 }
3935 
3936 static inline void muxnet_get(struct gsm_mux_net *mux_net)
3937 {
3938 	kref_get(&mux_net->ref);
3939 }
3940 
3941 static inline void muxnet_put(struct gsm_mux_net *mux_net)
3942 {
3943 	kref_put(&mux_net->ref, net_free);
3944 }
3945 
3946 static netdev_tx_t gsm_mux_net_start_xmit(struct sk_buff *skb,
3947 				      struct net_device *net)
3948 {
3949 	struct gsm_mux_net *mux_net = netdev_priv(net);
3950 	struct gsm_dlci *dlci = mux_net->dlci;
3951 	muxnet_get(mux_net);
3952 
3953 	skb_queue_head(&dlci->skb_list, skb);
3954 	net->stats.tx_packets++;
3955 	net->stats.tx_bytes += skb->len;
3956 	gsm_dlci_data_kick(dlci);
3957 	/* And tell the kernel when the last transmit started. */
3958 	netif_trans_update(net);
3959 	muxnet_put(mux_net);
3960 	return NETDEV_TX_OK;
3961 }
3962 
3963 /* called when a packet did not ack after watchdogtimeout */
3964 static void gsm_mux_net_tx_timeout(struct net_device *net, unsigned int txqueue)
3965 {
3966 	/* Tell syslog we are hosed. */
3967 	dev_dbg(&net->dev, "Tx timed out.\n");
3968 
3969 	/* Update statistics */
3970 	net->stats.tx_errors++;
3971 }
3972 
3973 static void gsm_mux_rx_netchar(struct gsm_dlci *dlci, const u8 *in_buf, int size)
3974 {
3975 	struct net_device *net = dlci->net;
3976 	struct sk_buff *skb;
3977 	struct gsm_mux_net *mux_net = netdev_priv(net);
3978 	muxnet_get(mux_net);
3979 
3980 	/* Allocate an sk_buff */
3981 	skb = dev_alloc_skb(size + NET_IP_ALIGN);
3982 	if (!skb) {
3983 		/* We got no receive buffer. */
3984 		net->stats.rx_dropped++;
3985 		muxnet_put(mux_net);
3986 		return;
3987 	}
3988 	skb_reserve(skb, NET_IP_ALIGN);
3989 	skb_put_data(skb, in_buf, size);
3990 
3991 	skb->dev = net;
3992 	skb->protocol = htons(ETH_P_IP);
3993 
3994 	/* Ship it off to the kernel */
3995 	netif_rx(skb);
3996 
3997 	/* update out statistics */
3998 	net->stats.rx_packets++;
3999 	net->stats.rx_bytes += size;
4000 	muxnet_put(mux_net);
4001 	return;
4002 }
4003 
4004 static void gsm_mux_net_init(struct net_device *net)
4005 {
4006 	static const struct net_device_ops gsm_netdev_ops = {
4007 		.ndo_open		= gsm_mux_net_open,
4008 		.ndo_stop		= gsm_mux_net_close,
4009 		.ndo_start_xmit		= gsm_mux_net_start_xmit,
4010 		.ndo_tx_timeout		= gsm_mux_net_tx_timeout,
4011 	};
4012 
4013 	net->netdev_ops = &gsm_netdev_ops;
4014 
4015 	/* fill in the other fields */
4016 	net->watchdog_timeo = GSM_NET_TX_TIMEOUT;
4017 	net->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
4018 	net->type = ARPHRD_NONE;
4019 	net->tx_queue_len = 10;
4020 }
4021 
4022 
4023 /* caller holds the dlci mutex */
4024 static void gsm_destroy_network(struct gsm_dlci *dlci)
4025 {
4026 	struct gsm_mux_net *mux_net;
4027 
4028 	pr_debug("destroy network interface\n");
4029 	if (!dlci->net)
4030 		return;
4031 	mux_net = netdev_priv(dlci->net);
4032 	muxnet_put(mux_net);
4033 }
4034 
4035 
4036 /* caller holds the dlci mutex */
4037 static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc)
4038 {
4039 	char *netname;
4040 	int retval = 0;
4041 	struct net_device *net;
4042 	struct gsm_mux_net *mux_net;
4043 
4044 	if (!capable(CAP_NET_ADMIN))
4045 		return -EPERM;
4046 
4047 	/* Already in a non tty mode */
4048 	if (dlci->adaption > 2)
4049 		return -EBUSY;
4050 
4051 	if (nc->protocol != htons(ETH_P_IP))
4052 		return -EPROTONOSUPPORT;
4053 
4054 	if (nc->adaption != 3 && nc->adaption != 4)
4055 		return -EPROTONOSUPPORT;
4056 
4057 	pr_debug("create network interface\n");
4058 
4059 	netname = "gsm%d";
4060 	if (nc->if_name[0] != '\0')
4061 		netname = nc->if_name;
4062 	net = alloc_netdev(sizeof(struct gsm_mux_net), netname,
4063 			   NET_NAME_UNKNOWN, gsm_mux_net_init);
4064 	if (!net) {
4065 		pr_err("alloc_netdev failed\n");
4066 		return -ENOMEM;
4067 	}
4068 	net->mtu = dlci->mtu;
4069 	net->min_mtu = MIN_MTU;
4070 	net->max_mtu = dlci->mtu;
4071 	mux_net = netdev_priv(net);
4072 	mux_net->dlci = dlci;
4073 	kref_init(&mux_net->ref);
4074 	strscpy(nc->if_name, net->name); /* return net name */
4075 
4076 	/* reconfigure dlci for network */
4077 	dlci->prev_adaption = dlci->adaption;
4078 	dlci->prev_data = dlci->data;
4079 	dlci->adaption = nc->adaption;
4080 	dlci->data = gsm_mux_rx_netchar;
4081 	dlci->net = net;
4082 
4083 	pr_debug("register netdev\n");
4084 	retval = register_netdev(net);
4085 	if (retval) {
4086 		pr_err("network register fail %d\n", retval);
4087 		dlci_net_free(dlci);
4088 		return retval;
4089 	}
4090 	return net->ifindex;	/* return network index */
4091 }
4092 
4093 /* Line discipline for real tty */
4094 static struct tty_ldisc_ops tty_ldisc_packet = {
4095 	.owner		 = THIS_MODULE,
4096 	.num		 = N_GSM0710,
4097 	.name            = "n_gsm",
4098 	.open            = gsmld_open,
4099 	.close           = gsmld_close,
4100 	.flush_buffer    = gsmld_flush_buffer,
4101 	.read            = gsmld_read,
4102 	.write           = gsmld_write,
4103 	.ioctl           = gsmld_ioctl,
4104 	.poll            = gsmld_poll,
4105 	.receive_buf     = gsmld_receive_buf,
4106 	.write_wakeup    = gsmld_write_wakeup
4107 };
4108 
4109 /*
4110  *	Virtual tty side
4111  */
4112 
4113 /**
4114  *	gsm_modem_upd_via_data	-	send modem bits via convergence layer
4115  *	@dlci: channel
4116  *	@brk: break signal
4117  *
4118  *	Send an empty frame to signal mobile state changes and to transmit the
4119  *	break signal for adaption 2.
4120  */
4121 
4122 static void gsm_modem_upd_via_data(struct gsm_dlci *dlci, u8 brk)
4123 {
4124 	struct gsm_mux *gsm = dlci->gsm;
4125 	unsigned long flags;
4126 
4127 	if (dlci->state != DLCI_OPEN || dlci->adaption != 2)
4128 		return;
4129 
4130 	spin_lock_irqsave(&gsm->tx_lock, flags);
4131 	gsm_dlci_modem_output(gsm, dlci, brk);
4132 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
4133 }
4134 
4135 /**
4136  *	gsm_modem_upd_via_msc	-	send modem bits via control frame
4137  *	@dlci: channel
4138  *	@brk: break signal
4139  */
4140 
4141 static int gsm_modem_upd_via_msc(struct gsm_dlci *dlci, u8 brk)
4142 {
4143 	u8 modembits[3];
4144 	struct gsm_control *ctrl;
4145 	int len = 2;
4146 
4147 	if (dlci->gsm->encoding != GSM_BASIC_OPT)
4148 		return 0;
4149 
4150 	modembits[0] = (dlci->addr << 2) | 2 | EA;  /* DLCI, Valid, EA */
4151 	if (!brk) {
4152 		modembits[1] = (gsm_encode_modem(dlci) << 1) | EA;
4153 	} else {
4154 		modembits[1] = gsm_encode_modem(dlci) << 1;
4155 		modembits[2] = (brk << 4) | 2 | EA; /* Length, Break, EA */
4156 		len++;
4157 	}
4158 	ctrl = gsm_control_send(dlci->gsm, CMD_MSC, modembits, len);
4159 	if (ctrl == NULL)
4160 		return -ENOMEM;
4161 	return gsm_control_wait(dlci->gsm, ctrl);
4162 }
4163 
4164 /**
4165  *	gsm_modem_update	-	send modem status line state
4166  *	@dlci: channel
4167  *	@brk: break signal
4168  */
4169 
4170 static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk)
4171 {
4172 	if (dlci->gsm->dead)
4173 		return -EL2HLT;
4174 	if (dlci->adaption == 2) {
4175 		/* Send convergence layer type 2 empty data frame. */
4176 		gsm_modem_upd_via_data(dlci, brk);
4177 		return 0;
4178 	} else if (dlci->gsm->encoding == GSM_BASIC_OPT) {
4179 		/* Send as MSC control message. */
4180 		return gsm_modem_upd_via_msc(dlci, brk);
4181 	}
4182 
4183 	/* Modem status lines are not supported. */
4184 	return -EPROTONOSUPPORT;
4185 }
4186 
4187 /**
4188  * gsm_wait_modem_change - wait for modem status line change
4189  * @dlci: channel
4190  * @mask: modem status line bits
4191  *
4192  * The function returns if:
4193  * - any given modem status line bit changed
4194  * - the wait event function got interrupted (e.g. by a signal)
4195  * - the underlying DLCI was closed
4196  * - the underlying ldisc device was removed
4197  */
4198 static int gsm_wait_modem_change(struct gsm_dlci *dlci, u32 mask)
4199 {
4200 	struct gsm_mux *gsm = dlci->gsm;
4201 	u32 old = dlci->modem_rx;
4202 	int ret;
4203 
4204 	ret = wait_event_interruptible(gsm->event, gsm->dead ||
4205 				       dlci->state != DLCI_OPEN ||
4206 				       (old ^ dlci->modem_rx) & mask);
4207 	if (gsm->dead)
4208 		return -ENODEV;
4209 	if (dlci->state != DLCI_OPEN)
4210 		return -EL2NSYNC;
4211 	return ret;
4212 }
4213 
4214 static bool gsm_carrier_raised(struct tty_port *port)
4215 {
4216 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
4217 	struct gsm_mux *gsm = dlci->gsm;
4218 
4219 	/* Not yet open so no carrier info */
4220 	if (dlci->state != DLCI_OPEN)
4221 		return false;
4222 	if (debug & DBG_CD_ON)
4223 		return true;
4224 
4225 	/*
4226 	 * Basic mode with control channel in ADM mode may not respond
4227 	 * to CMD_MSC at all and modem_rx is empty.
4228 	 */
4229 	if (gsm->encoding == GSM_BASIC_OPT &&
4230 	    gsm->dlci[0]->mode == DLCI_MODE_ADM && !dlci->modem_rx)
4231 		return true;
4232 
4233 	return dlci->modem_rx & TIOCM_CD;
4234 }
4235 
4236 static void gsm_dtr_rts(struct tty_port *port, bool active)
4237 {
4238 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
4239 	unsigned int modem_tx = dlci->modem_tx;
4240 	if (active)
4241 		modem_tx |= TIOCM_DTR | TIOCM_RTS;
4242 	else
4243 		modem_tx &= ~(TIOCM_DTR | TIOCM_RTS);
4244 	if (modem_tx != dlci->modem_tx) {
4245 		dlci->modem_tx = modem_tx;
4246 		gsm_modem_update(dlci, 0);
4247 	}
4248 }
4249 
4250 static const struct tty_port_operations gsm_port_ops = {
4251 	.carrier_raised = gsm_carrier_raised,
4252 	.dtr_rts = gsm_dtr_rts,
4253 	.destruct = gsm_dlci_free,
4254 };
4255 
4256 static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
4257 {
4258 	struct gsm_mux *gsm;
4259 	struct gsm_dlci *dlci, *dlci0;
4260 	unsigned int line = tty->index;
4261 	unsigned int mux = mux_line_to_num(line);
4262 	bool alloc = false;
4263 	int ret;
4264 
4265 	line = line & 0x3F;
4266 
4267 	if (mux >= MAX_MUX)
4268 		return -ENXIO;
4269 	/* FIXME: we need to lock gsm_mux for lifetimes of ttys eventually */
4270 	if (gsm_mux[mux] == NULL)
4271 		return -EUNATCH;
4272 	if (line == 0 || line > 61)	/* 62/63 reserved */
4273 		return -ECHRNG;
4274 	gsm = gsm_mux[mux];
4275 	if (gsm->dead)
4276 		return -EL2HLT;
4277 	/* If DLCI 0 is not yet fully open return an error.
4278 	This is ok from a locking
4279 	perspective as we don't have to worry about this
4280 	if DLCI0 is lost */
4281 	mutex_lock(&gsm->mutex);
4282 
4283 	dlci0 = gsm->dlci[0];
4284 	if (dlci0 && dlci0->state != DLCI_OPEN) {
4285 		mutex_unlock(&gsm->mutex);
4286 
4287 		if (dlci0->state == DLCI_OPENING)
4288 			wait_event(gsm->event, dlci0->state != DLCI_OPENING);
4289 
4290 		if (dlci0->state != DLCI_OPEN)
4291 			return -EL2NSYNC;
4292 
4293 		mutex_lock(&gsm->mutex);
4294 	}
4295 
4296 	dlci = gsm->dlci[line];
4297 	if (dlci == NULL) {
4298 		alloc = true;
4299 		dlci = gsm_dlci_alloc(gsm, line);
4300 	}
4301 	if (dlci == NULL) {
4302 		mutex_unlock(&gsm->mutex);
4303 		return -ENOMEM;
4304 	}
4305 	ret = tty_port_install(&dlci->port, driver, tty);
4306 	if (ret) {
4307 		if (alloc)
4308 			dlci_put(dlci);
4309 		mutex_unlock(&gsm->mutex);
4310 		return ret;
4311 	}
4312 
4313 	dlci_get(dlci);
4314 	dlci_get(gsm->dlci[0]);
4315 	mux_get(gsm);
4316 	tty->driver_data = dlci;
4317 	mutex_unlock(&gsm->mutex);
4318 
4319 	return 0;
4320 }
4321 
4322 static int gsmtty_open(struct tty_struct *tty, struct file *filp)
4323 {
4324 	struct gsm_dlci *dlci = tty->driver_data;
4325 	struct tty_port *port = &dlci->port;
4326 
4327 	port->count++;
4328 	tty_port_tty_set(port, tty);
4329 
4330 	dlci->modem_rx = 0;
4331 	/* We could in theory open and close before we wait - eg if we get
4332 	   a DM straight back. This is ok as that will have caused a hangup */
4333 	tty_port_set_initialized(port, true);
4334 	/* Start sending off SABM messages */
4335 	if (!dlci->gsm->wait_config) {
4336 		/* Start sending off SABM messages */
4337 		if (dlci->gsm->initiator)
4338 			gsm_dlci_begin_open(dlci);
4339 		else
4340 			gsm_dlci_set_opening(dlci);
4341 	} else {
4342 		gsm_dlci_set_wait_config(dlci);
4343 	}
4344 	/* And wait for virtual carrier */
4345 	return tty_port_block_til_ready(port, tty, filp);
4346 }
4347 
4348 static void gsmtty_close(struct tty_struct *tty, struct file *filp)
4349 {
4350 	struct gsm_dlci *dlci = tty->driver_data;
4351 
4352 	if (dlci == NULL)
4353 		return;
4354 	if (dlci->state == DLCI_CLOSED)
4355 		return;
4356 	mutex_lock(&dlci->mutex);
4357 	gsm_destroy_network(dlci);
4358 	mutex_unlock(&dlci->mutex);
4359 	if (tty_port_close_start(&dlci->port, tty, filp) == 0)
4360 		return;
4361 	gsm_dlci_begin_close(dlci);
4362 	if (tty_port_initialized(&dlci->port) && C_HUPCL(tty))
4363 		tty_port_lower_dtr_rts(&dlci->port);
4364 	tty_port_close_end(&dlci->port, tty);
4365 	tty_port_tty_set(&dlci->port, NULL);
4366 	return;
4367 }
4368 
4369 static void gsmtty_hangup(struct tty_struct *tty)
4370 {
4371 	struct gsm_dlci *dlci = tty->driver_data;
4372 	if (dlci->state == DLCI_CLOSED)
4373 		return;
4374 	tty_port_hangup(&dlci->port);
4375 	gsm_dlci_begin_close(dlci);
4376 }
4377 
4378 static ssize_t gsmtty_write(struct tty_struct *tty, const u8 *buf, size_t len)
4379 {
4380 	int sent;
4381 	struct gsm_dlci *dlci = tty->driver_data;
4382 	if (dlci->state == DLCI_CLOSED)
4383 		return -EINVAL;
4384 	/* Stuff the bytes into the fifo queue */
4385 	sent = kfifo_in_locked(&dlci->fifo, buf, len, &dlci->lock);
4386 	/* Need to kick the channel */
4387 	gsm_dlci_data_kick(dlci);
4388 	return sent;
4389 }
4390 
4391 static unsigned int gsmtty_write_room(struct tty_struct *tty)
4392 {
4393 	struct gsm_dlci *dlci = tty->driver_data;
4394 	if (dlci->state == DLCI_CLOSED)
4395 		return 0;
4396 	return kfifo_avail(&dlci->fifo);
4397 }
4398 
4399 static unsigned int gsmtty_chars_in_buffer(struct tty_struct *tty)
4400 {
4401 	struct gsm_dlci *dlci = tty->driver_data;
4402 	if (dlci->state == DLCI_CLOSED)
4403 		return 0;
4404 	return kfifo_len(&dlci->fifo);
4405 }
4406 
4407 static void gsmtty_flush_buffer(struct tty_struct *tty)
4408 {
4409 	struct gsm_dlci *dlci = tty->driver_data;
4410 	unsigned long flags;
4411 
4412 	if (dlci->state == DLCI_CLOSED)
4413 		return;
4414 	/* Caution needed: If we implement reliable transport classes
4415 	   then the data being transmitted can't simply be junked once
4416 	   it has first hit the stack. Until then we can just blow it
4417 	   away */
4418 	spin_lock_irqsave(&dlci->lock, flags);
4419 	kfifo_reset(&dlci->fifo);
4420 	spin_unlock_irqrestore(&dlci->lock, flags);
4421 	/* Need to unhook this DLCI from the transmit queue logic */
4422 }
4423 
4424 static void gsmtty_wait_until_sent(struct tty_struct *tty, int timeout)
4425 {
4426 	/* The FIFO handles the queue so the kernel will do the right
4427 	   thing waiting on chars_in_buffer before calling us. No work
4428 	   to do here */
4429 }
4430 
4431 static int gsmtty_tiocmget(struct tty_struct *tty)
4432 {
4433 	struct gsm_dlci *dlci = tty->driver_data;
4434 	if (dlci->state == DLCI_CLOSED)
4435 		return -EINVAL;
4436 	return dlci->modem_rx;
4437 }
4438 
4439 static int gsmtty_tiocmset(struct tty_struct *tty,
4440 	unsigned int set, unsigned int clear)
4441 {
4442 	struct gsm_dlci *dlci = tty->driver_data;
4443 	unsigned int modem_tx = dlci->modem_tx;
4444 
4445 	if (dlci->state == DLCI_CLOSED)
4446 		return -EINVAL;
4447 	modem_tx &= ~clear;
4448 	modem_tx |= set;
4449 
4450 	if (modem_tx != dlci->modem_tx) {
4451 		dlci->modem_tx = modem_tx;
4452 		return gsm_modem_update(dlci, 0);
4453 	}
4454 	return 0;
4455 }
4456 
4457 
4458 static int gsmtty_ioctl(struct tty_struct *tty,
4459 			unsigned int cmd, unsigned long arg)
4460 {
4461 	struct gsm_dlci *dlci = tty->driver_data;
4462 	struct gsm_netconfig nc;
4463 	struct gsm_dlci_config dc;
4464 	int index;
4465 
4466 	if (dlci->state == DLCI_CLOSED)
4467 		return -EINVAL;
4468 	switch (cmd) {
4469 	case GSMIOC_ENABLE_NET:
4470 		if (copy_from_user(&nc, (void __user *)arg, sizeof(nc)))
4471 			return -EFAULT;
4472 		nc.if_name[IFNAMSIZ-1] = '\0';
4473 		/* return net interface index or error code */
4474 		mutex_lock(&dlci->mutex);
4475 		index = gsm_create_network(dlci, &nc);
4476 		mutex_unlock(&dlci->mutex);
4477 		if (copy_to_user((void __user *)arg, &nc, sizeof(nc)))
4478 			return -EFAULT;
4479 		return index;
4480 	case GSMIOC_DISABLE_NET:
4481 		if (!capable(CAP_NET_ADMIN))
4482 			return -EPERM;
4483 		mutex_lock(&dlci->mutex);
4484 		gsm_destroy_network(dlci);
4485 		mutex_unlock(&dlci->mutex);
4486 		return 0;
4487 	case GSMIOC_GETCONF_DLCI:
4488 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
4489 			return -EFAULT;
4490 		if (dc.channel != dlci->addr)
4491 			return -EPERM;
4492 		gsm_dlci_copy_config_values(dlci, &dc);
4493 		if (copy_to_user((void __user *)arg, &dc, sizeof(dc)))
4494 			return -EFAULT;
4495 		return 0;
4496 	case GSMIOC_SETCONF_DLCI:
4497 		if (copy_from_user(&dc, (void __user *)arg, sizeof(dc)))
4498 			return -EFAULT;
4499 		if (dc.channel >= NUM_DLCI)
4500 			return -EINVAL;
4501 		if (dc.channel != 0 && dc.channel != dlci->addr)
4502 			return -EPERM;
4503 		return gsm_dlci_config(dlci, &dc, 1);
4504 	case TIOCMIWAIT:
4505 		return gsm_wait_modem_change(dlci, (u32)arg);
4506 	default:
4507 		return -ENOIOCTLCMD;
4508 	}
4509 }
4510 
4511 static void gsmtty_set_termios(struct tty_struct *tty,
4512 			       const struct ktermios *old)
4513 {
4514 	struct gsm_dlci *dlci = tty->driver_data;
4515 	if (dlci->state == DLCI_CLOSED)
4516 		return;
4517 	/* For the moment its fixed. In actual fact the speed information
4518 	   for the virtual channel can be propogated in both directions by
4519 	   the RPN control message. This however rapidly gets nasty as we
4520 	   then have to remap modem signals each way according to whether
4521 	   our virtual cable is null modem etc .. */
4522 	tty_termios_copy_hw(&tty->termios, old);
4523 }
4524 
4525 static void gsmtty_throttle(struct tty_struct *tty)
4526 {
4527 	struct gsm_dlci *dlci = tty->driver_data;
4528 	if (dlci->state == DLCI_CLOSED)
4529 		return;
4530 	if (C_CRTSCTS(tty))
4531 		dlci->modem_tx &= ~TIOCM_RTS;
4532 	dlci->throttled = true;
4533 	/* Send an MSC with RTS cleared */
4534 	gsm_modem_update(dlci, 0);
4535 }
4536 
4537 static void gsmtty_unthrottle(struct tty_struct *tty)
4538 {
4539 	struct gsm_dlci *dlci = tty->driver_data;
4540 	if (dlci->state == DLCI_CLOSED)
4541 		return;
4542 	if (C_CRTSCTS(tty))
4543 		dlci->modem_tx |= TIOCM_RTS;
4544 	dlci->throttled = false;
4545 	/* Send an MSC with RTS set */
4546 	gsm_modem_update(dlci, 0);
4547 }
4548 
4549 static int gsmtty_break_ctl(struct tty_struct *tty, int state)
4550 {
4551 	struct gsm_dlci *dlci = tty->driver_data;
4552 	int encode = 0;	/* Off */
4553 	if (dlci->state == DLCI_CLOSED)
4554 		return -EINVAL;
4555 
4556 	if (state == -1)	/* "On indefinitely" - we can't encode this
4557 				    properly */
4558 		encode = 0x0F;
4559 	else if (state > 0) {
4560 		encode = state / 200;	/* mS to encoding */
4561 		if (encode > 0x0F)
4562 			encode = 0x0F;	/* Best effort */
4563 	}
4564 	return gsm_modem_update(dlci, encode);
4565 }
4566 
4567 static void gsmtty_cleanup(struct tty_struct *tty)
4568 {
4569 	struct gsm_dlci *dlci = tty->driver_data;
4570 	struct gsm_mux *gsm = dlci->gsm;
4571 
4572 	dlci_put(dlci);
4573 	dlci_put(gsm->dlci[0]);
4574 	mux_put(gsm);
4575 }
4576 
4577 /* Virtual ttys for the demux */
4578 static const struct tty_operations gsmtty_ops = {
4579 	.install		= gsmtty_install,
4580 	.open			= gsmtty_open,
4581 	.close			= gsmtty_close,
4582 	.write			= gsmtty_write,
4583 	.write_room		= gsmtty_write_room,
4584 	.chars_in_buffer	= gsmtty_chars_in_buffer,
4585 	.flush_buffer		= gsmtty_flush_buffer,
4586 	.ioctl			= gsmtty_ioctl,
4587 	.throttle		= gsmtty_throttle,
4588 	.unthrottle		= gsmtty_unthrottle,
4589 	.set_termios		= gsmtty_set_termios,
4590 	.hangup			= gsmtty_hangup,
4591 	.wait_until_sent	= gsmtty_wait_until_sent,
4592 	.tiocmget		= gsmtty_tiocmget,
4593 	.tiocmset		= gsmtty_tiocmset,
4594 	.break_ctl		= gsmtty_break_ctl,
4595 	.cleanup		= gsmtty_cleanup,
4596 };
4597 
4598 
4599 
4600 static int __init gsm_init(void)
4601 {
4602 	/* Fill in our line protocol discipline, and register it */
4603 	int status = tty_register_ldisc(&tty_ldisc_packet);
4604 	if (status != 0) {
4605 		pr_err("n_gsm: can't register line discipline (err = %d)\n",
4606 								status);
4607 		return status;
4608 	}
4609 
4610 	gsm_tty_driver = tty_alloc_driver(GSM_TTY_MINORS, TTY_DRIVER_REAL_RAW |
4611 			TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_HARDWARE_BREAK);
4612 	if (IS_ERR(gsm_tty_driver)) {
4613 		pr_err("gsm_init: tty allocation failed.\n");
4614 		status = PTR_ERR(gsm_tty_driver);
4615 		goto err_unreg_ldisc;
4616 	}
4617 	gsm_tty_driver->driver_name	= "gsmtty";
4618 	gsm_tty_driver->name		= "gsmtty";
4619 	gsm_tty_driver->major		= 0;	/* Dynamic */
4620 	gsm_tty_driver->minor_start	= 0;
4621 	gsm_tty_driver->type		= TTY_DRIVER_TYPE_SERIAL;
4622 	gsm_tty_driver->subtype	= SERIAL_TYPE_NORMAL;
4623 	gsm_tty_driver->init_termios	= tty_std_termios;
4624 	/* Fixme */
4625 	gsm_tty_driver->init_termios.c_lflag &= ~ECHO;
4626 	tty_set_operations(gsm_tty_driver, &gsmtty_ops);
4627 
4628 	if (tty_register_driver(gsm_tty_driver)) {
4629 		pr_err("gsm_init: tty registration failed.\n");
4630 		status = -EBUSY;
4631 		goto err_put_driver;
4632 	}
4633 	pr_debug("gsm_init: loaded as %d,%d.\n",
4634 			gsm_tty_driver->major, gsm_tty_driver->minor_start);
4635 	return 0;
4636 err_put_driver:
4637 	tty_driver_kref_put(gsm_tty_driver);
4638 err_unreg_ldisc:
4639 	tty_unregister_ldisc(&tty_ldisc_packet);
4640 	return status;
4641 }
4642 
4643 static void __exit gsm_exit(void)
4644 {
4645 	tty_unregister_ldisc(&tty_ldisc_packet);
4646 	tty_unregister_driver(gsm_tty_driver);
4647 	tty_driver_kref_put(gsm_tty_driver);
4648 }
4649 
4650 module_init(gsm_init);
4651 module_exit(gsm_exit);
4652 
4653 
4654 MODULE_DESCRIPTION("GSM 0710 tty multiplexor");
4655 MODULE_LICENSE("GPL");
4656 MODULE_ALIAS_LDISC(N_GSM0710);
4657