1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) ST-Ericsson AB 2010
4 * Author: Sjur Brendeland
5 */
6
7 #include <linux/hardirq.h>
8 #include <linux/init.h>
9 #include <linux/module.h>
10 #include <linux/device.h>
11 #include <linux/types.h>
12 #include <linux/skbuff.h>
13 #include <linux/netdevice.h>
14 #include <linux/rtnetlink.h>
15 #include <linux/tty.h>
16 #include <linux/file.h>
17 #include <linux/if_arp.h>
18 #include <net/caif/caif_device.h>
19 #include <net/caif/cfcnfg.h>
20 #include <linux/err.h>
21 #include <linux/debugfs.h>
22
23 MODULE_LICENSE("GPL");
24 MODULE_AUTHOR("Sjur Brendeland");
25 MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
26 MODULE_LICENSE("GPL");
27 MODULE_ALIAS_LDISC(N_CAIF);
28
29 #define SEND_QUEUE_LOW 10
30 #define SEND_QUEUE_HIGH 100
31 #define CAIF_SENDING 1 /* Bit 1 = 0x02*/
32 #define CAIF_FLOW_OFF_SENT 4 /* Bit 4 = 0x10 */
33 #define MAX_WRITE_CHUNK 4096
34 #define ON 1
35 #define OFF 0
36 #define CAIF_MAX_MTU 4096
37
38 static DEFINE_SPINLOCK(ser_lock);
39 static LIST_HEAD(ser_list);
40 static LIST_HEAD(ser_release_list);
41
42 static bool ser_loop;
43 module_param(ser_loop, bool, 0444);
44 MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
45
46 static bool ser_use_stx = true;
47 module_param(ser_use_stx, bool, 0444);
48 MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
49
50 static bool ser_use_fcs = true;
51
52 module_param(ser_use_fcs, bool, 0444);
53 MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
54
55 static int ser_write_chunk = MAX_WRITE_CHUNK;
56 module_param(ser_write_chunk, int, 0444);
57
58 MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
59
60 static struct dentry *debugfsdir;
61
62 static int caif_net_open(struct net_device *dev);
63 static int caif_net_close(struct net_device *dev);
64
65 struct ser_device {
66 struct caif_dev_common common;
67 struct list_head node;
68 struct net_device *dev;
69 struct sk_buff_head head;
70 struct tty_struct *tty;
71 bool tx_started;
72 unsigned long state;
73 #ifdef CONFIG_DEBUG_FS
74 struct dentry *debugfs_tty_dir;
75 struct debugfs_blob_wrapper tx_blob;
76 struct debugfs_blob_wrapper rx_blob;
77 u8 rx_data[128];
78 u8 tx_data[128];
79 u8 tty_status;
80
81 #endif
82 };
83
84 static void caifdev_setup(struct net_device *dev);
85 static void ldisc_tx_wakeup(struct tty_struct *tty);
86 #ifdef CONFIG_DEBUG_FS
update_tty_status(struct ser_device * ser)87 static inline void update_tty_status(struct ser_device *ser)
88 {
89 ser->tty_status =
90 ser->tty->flow.stopped << 5 |
91 ser->tty->flow.tco_stopped << 3 |
92 ser->tty->ctrl.packet << 2;
93 }
debugfs_init(struct ser_device * ser,struct tty_struct * tty)94 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
95 {
96 ser->debugfs_tty_dir = debugfs_create_dir(tty->name, debugfsdir);
97
98 debugfs_create_blob("last_tx_msg", 0400, ser->debugfs_tty_dir,
99 &ser->tx_blob);
100
101 debugfs_create_blob("last_rx_msg", 0400, ser->debugfs_tty_dir,
102 &ser->rx_blob);
103
104 debugfs_create_xul("ser_state", 0400, ser->debugfs_tty_dir,
105 &ser->state);
106
107 debugfs_create_x8("tty_status", 0400, ser->debugfs_tty_dir,
108 &ser->tty_status);
109
110 ser->tx_blob.data = ser->tx_data;
111 ser->tx_blob.size = 0;
112 ser->rx_blob.data = ser->rx_data;
113 ser->rx_blob.size = 0;
114 }
115
debugfs_deinit(struct ser_device * ser)116 static inline void debugfs_deinit(struct ser_device *ser)
117 {
118 debugfs_remove_recursive(ser->debugfs_tty_dir);
119 }
120
debugfs_rx(struct ser_device * ser,const u8 * data,int size)121 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
122 {
123 if (size > sizeof(ser->rx_data))
124 size = sizeof(ser->rx_data);
125 memcpy(ser->rx_data, data, size);
126 ser->rx_blob.data = ser->rx_data;
127 ser->rx_blob.size = size;
128 }
129 #else
debugfs_init(struct ser_device * ser,struct tty_struct * tty)130 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
131 {
132 }
133
debugfs_deinit(struct ser_device * ser)134 static inline void debugfs_deinit(struct ser_device *ser)
135 {
136 }
137
update_tty_status(struct ser_device * ser)138 static inline void update_tty_status(struct ser_device *ser)
139 {
140 }
141
debugfs_rx(struct ser_device * ser,const u8 * data,int size)142 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
143 {
144 }
145 #endif
146
ldisc_receive(struct tty_struct * tty,const u8 * data,const u8 * flags,size_t count)147 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
148 const u8 *flags, size_t count)
149 {
150 struct sk_buff *skb = NULL;
151 struct ser_device *ser;
152 int ret;
153
154 ser = tty->disc_data;
155
156 /*
157 * NOTE: flags may contain information about break or overrun.
158 * This is not yet handled.
159 */
160
161
162 /*
163 * Workaround for garbage at start of transmission,
164 * only enable if STX handling is not enabled.
165 */
166 if (!ser->common.use_stx && !ser->tx_started) {
167 dev_info(&ser->dev->dev,
168 "Bytes received before initial transmission -"
169 "bytes discarded.\n");
170 return;
171 }
172
173 BUG_ON(ser->dev == NULL);
174
175 /* Get a suitable caif packet and copy in data. */
176 skb = netdev_alloc_skb(ser->dev, count+1);
177 if (skb == NULL)
178 return;
179 skb_put_data(skb, data, count);
180
181 skb->protocol = htons(ETH_P_CAIF);
182 skb_reset_mac_header(skb);
183 debugfs_rx(ser, data, count);
184 /* Push received packet up the stack. */
185 ret = netif_rx(skb);
186 if (!ret) {
187 ser->dev->stats.rx_packets++;
188 ser->dev->stats.rx_bytes += count;
189 } else
190 ++ser->dev->stats.rx_dropped;
191 update_tty_status(ser);
192 }
193
handle_tx(struct ser_device * ser)194 static int handle_tx(struct ser_device *ser)
195 {
196 struct tty_struct *tty;
197 struct sk_buff *skb;
198 int tty_wr, len, room;
199
200 tty = ser->tty;
201 ser->tx_started = true;
202
203 /* Enter critical section */
204 if (test_and_set_bit(CAIF_SENDING, &ser->state))
205 return 0;
206
207 /* skb_peek is safe because handle_tx is called after skb_queue_tail */
208 while ((skb = skb_peek(&ser->head)) != NULL) {
209
210 /* Make sure you don't write too much */
211 len = skb->len;
212 room = tty_write_room(tty);
213 if (!room)
214 break;
215 if (room > ser_write_chunk)
216 room = ser_write_chunk;
217 if (len > room)
218 len = room;
219
220 /* Write to tty or loopback */
221 if (!ser_loop) {
222 tty_wr = tty->ops->write(tty, skb->data, len);
223 update_tty_status(ser);
224 } else {
225 tty_wr = len;
226 ldisc_receive(tty, skb->data, NULL, len);
227 }
228 ser->dev->stats.tx_packets++;
229 ser->dev->stats.tx_bytes += tty_wr;
230
231 /* Error on TTY ?! */
232 if (tty_wr < 0)
233 goto error;
234 /* Reduce buffer written, and discard if empty */
235 skb_pull(skb, tty_wr);
236 if (skb->len == 0) {
237 struct sk_buff *tmp = skb_dequeue(&ser->head);
238 WARN_ON(tmp != skb);
239 dev_consume_skb_any(skb);
240 }
241 }
242 /* Send flow off if queue is empty */
243 if (ser->head.qlen <= SEND_QUEUE_LOW &&
244 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
245 ser->common.flowctrl != NULL)
246 ser->common.flowctrl(ser->dev, ON);
247 clear_bit(CAIF_SENDING, &ser->state);
248 return 0;
249 error:
250 clear_bit(CAIF_SENDING, &ser->state);
251 return tty_wr;
252 }
253
caif_xmit(struct sk_buff * skb,struct net_device * dev)254 static netdev_tx_t caif_xmit(struct sk_buff *skb, struct net_device *dev)
255 {
256 struct ser_device *ser;
257
258 ser = netdev_priv(dev);
259
260 /* Send flow off once, on high water mark */
261 if (ser->head.qlen > SEND_QUEUE_HIGH &&
262 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
263 ser->common.flowctrl != NULL)
264
265 ser->common.flowctrl(ser->dev, OFF);
266
267 skb_queue_tail(&ser->head, skb);
268 return handle_tx(ser);
269 }
270
271
ldisc_tx_wakeup(struct tty_struct * tty)272 static void ldisc_tx_wakeup(struct tty_struct *tty)
273 {
274 struct ser_device *ser;
275
276 ser = tty->disc_data;
277 BUG_ON(ser == NULL);
278 WARN_ON(ser->tty != tty);
279 handle_tx(ser);
280 }
281
282
ser_release(struct work_struct * work)283 static void ser_release(struct work_struct *work)
284 {
285 struct list_head list;
286 struct ser_device *ser, *tmp;
287 struct tty_struct *tty;
288
289 spin_lock(&ser_lock);
290 list_replace_init(&ser_release_list, &list);
291 spin_unlock(&ser_lock);
292
293 if (!list_empty(&list)) {
294 rtnl_lock();
295 list_for_each_entry_safe(ser, tmp, &list, node) {
296 tty = ser->tty;
297 dev_close(ser->dev);
298 unregister_netdevice(ser->dev);
299 debugfs_deinit(ser);
300 tty_kref_put(tty->link);
301 tty_kref_put(tty);
302 }
303 rtnl_unlock();
304 }
305 }
306
307 static DECLARE_WORK(ser_release_work, ser_release);
308
ldisc_open(struct tty_struct * tty)309 static int ldisc_open(struct tty_struct *tty)
310 {
311 struct ser_device *ser;
312 struct net_device *dev;
313 char name[64];
314 int result;
315
316 /* No write no play */
317 if (tty->ops->write == NULL)
318 return -EOPNOTSUPP;
319 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
320 return -EPERM;
321
322 /* release devices to avoid name collision */
323 ser_release(NULL);
324
325 result = snprintf(name, sizeof(name), "cf%s", tty->name);
326 if (result >= IFNAMSIZ)
327 return -EINVAL;
328 dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
329 caifdev_setup);
330 if (!dev)
331 return -ENOMEM;
332
333 ser = netdev_priv(dev);
334 ser->tty = tty_kref_get(tty);
335 tty_kref_get(tty->link);
336 ser->dev = dev;
337 debugfs_init(ser, tty);
338 tty->receive_room = 4096;
339 tty->disc_data = ser;
340 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
341 rtnl_lock();
342 result = register_netdevice(dev);
343 if (result) {
344 tty_kref_put(tty->link);
345 tty_kref_put(tty);
346 rtnl_unlock();
347 free_netdev(dev);
348 return -ENODEV;
349 }
350
351 spin_lock(&ser_lock);
352 list_add(&ser->node, &ser_list);
353 spin_unlock(&ser_lock);
354 rtnl_unlock();
355 netif_stop_queue(dev);
356 update_tty_status(ser);
357 return 0;
358 }
359
ldisc_close(struct tty_struct * tty)360 static void ldisc_close(struct tty_struct *tty)
361 {
362 struct ser_device *ser = tty->disc_data;
363
364 spin_lock(&ser_lock);
365 list_move(&ser->node, &ser_release_list);
366 spin_unlock(&ser_lock);
367 schedule_work(&ser_release_work);
368 }
369
370 /* The line discipline structure. */
371 static struct tty_ldisc_ops caif_ldisc = {
372 .owner = THIS_MODULE,
373 .num = N_CAIF,
374 .name = "n_caif",
375 .open = ldisc_open,
376 .close = ldisc_close,
377 .receive_buf = ldisc_receive,
378 .write_wakeup = ldisc_tx_wakeup
379 };
380
381 static const struct net_device_ops netdev_ops = {
382 .ndo_open = caif_net_open,
383 .ndo_stop = caif_net_close,
384 .ndo_start_xmit = caif_xmit
385 };
386
caifdev_setup(struct net_device * dev)387 static void caifdev_setup(struct net_device *dev)
388 {
389 struct ser_device *serdev = netdev_priv(dev);
390
391 dev->features = 0;
392 dev->netdev_ops = &netdev_ops;
393 dev->type = ARPHRD_CAIF;
394 dev->flags = IFF_POINTOPOINT | IFF_NOARP;
395 dev->mtu = CAIF_MAX_MTU;
396 dev->priv_flags |= IFF_NO_QUEUE;
397 dev->needs_free_netdev = true;
398 skb_queue_head_init(&serdev->head);
399 serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
400 serdev->common.use_frag = true;
401 serdev->common.use_stx = ser_use_stx;
402 serdev->common.use_fcs = ser_use_fcs;
403 serdev->dev = dev;
404 }
405
406
caif_net_open(struct net_device * dev)407 static int caif_net_open(struct net_device *dev)
408 {
409 netif_wake_queue(dev);
410 return 0;
411 }
412
caif_net_close(struct net_device * dev)413 static int caif_net_close(struct net_device *dev)
414 {
415 netif_stop_queue(dev);
416 return 0;
417 }
418
caif_ser_init(void)419 static int __init caif_ser_init(void)
420 {
421 int ret;
422
423 ret = tty_register_ldisc(&caif_ldisc);
424 if (ret < 0)
425 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF, ret);
426
427 debugfsdir = debugfs_create_dir("caif_serial", NULL);
428 return ret;
429 }
430
caif_ser_exit(void)431 static void __exit caif_ser_exit(void)
432 {
433 spin_lock(&ser_lock);
434 list_splice(&ser_list, &ser_release_list);
435 spin_unlock(&ser_lock);
436 ser_release(NULL);
437 cancel_work_sync(&ser_release_work);
438 tty_unregister_ldisc(&caif_ldisc);
439 debugfs_remove_recursive(debugfsdir);
440 }
441
442 module_init(caif_ser_init);
443 module_exit(caif_ser_exit);
444