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
23MODULE_LICENSE("GPL");
24MODULE_AUTHOR("Sjur Brendeland");
25MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
26MODULE_LICENSE("GPL");
27MODULE_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
38static DEFINE_SPINLOCK(ser_lock);
39static LIST_HEAD(ser_list);
40static LIST_HEAD(ser_release_list);
41
42static bool ser_loop;
43module_param(ser_loop, bool, 0444);
44MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
45
46static bool ser_use_stx = true;
47module_param(ser_use_stx, bool, 0444);
48MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
49
50static bool ser_use_fcs = true;
51
52module_param(ser_use_fcs, bool, 0444);
53MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
54
55static int ser_write_chunk = MAX_WRITE_CHUNK;
56module_param(ser_write_chunk, int, 0444);
57
58MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
59
60static struct dentry *debugfsdir;
61
62static int caif_net_open(struct net_device *dev);
63static int caif_net_close(struct net_device *dev);
64
65struct 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
84static void caifdev_setup(struct net_device *dev);
85static void ldisc_tx_wakeup(struct tty_struct *tty);
86#ifdef CONFIG_DEBUG_FS
87static 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}
94static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
95{
96 ser->debugfs_tty_dir = debugfs_create_dir(name: tty->name, parent: debugfsdir);
97
98 debugfs_create_blob(name: "last_tx_msg", mode: 0400, parent: ser->debugfs_tty_dir,
99 blob: &ser->tx_blob);
100
101 debugfs_create_blob(name: "last_rx_msg", mode: 0400, parent: ser->debugfs_tty_dir,
102 blob: &ser->rx_blob);
103
104 debugfs_create_xul(name: "ser_state", mode: 0400, parent: ser->debugfs_tty_dir,
105 value: &ser->state);
106
107 debugfs_create_x8(name: "tty_status", mode: 0400, parent: ser->debugfs_tty_dir,
108 value: &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
116static inline void debugfs_deinit(struct ser_device *ser)
117{
118 debugfs_remove_recursive(dentry: ser->debugfs_tty_dir);
119}
120
121static 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
130static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
131{
132}
133
134static inline void debugfs_deinit(struct ser_device *ser)
135{
136}
137
138static inline void update_tty_status(struct ser_device *ser)
139{
140}
141
142static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
143{
144}
145#endif
146
147static 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(dev: ser->dev, length: count+1);
177 if (skb == NULL)
178 return;
179 skb_put_data(skb, data, len: count);
180
181 skb->protocol = htons(ETH_P_CAIF);
182 skb_reset_mac_header(skb);
183 debugfs_rx(ser, data, size: 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
194static 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, addr: &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(list_: &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, data: skb->data, NULL, count: 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, len: tty_wr);
236 if (skb->len == 0) {
237 struct sk_buff *tmp = skb_dequeue(list: &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, addr: &ser->state) &&
245 ser->common.flowctrl != NULL)
246 ser->common.flowctrl(ser->dev, ON);
247 clear_bit(CAIF_SENDING, addr: &ser->state);
248 return 0;
249error:
250 clear_bit(CAIF_SENDING, addr: &ser->state);
251 return tty_wr;
252}
253
254static 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, addr: &ser->state) &&
263 ser->common.flowctrl != NULL)
264
265 ser->common.flowctrl(ser->dev, OFF);
266
267 skb_queue_tail(list: &ser->head, newsk: skb);
268 return handle_tx(ser);
269}
270
271
272static 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
283static void ser_release(struct work_struct *work)
284{
285 struct list_head list;
286 struct ser_device *ser, *tmp;
287
288 spin_lock(lock: &ser_lock);
289 list_replace_init(old: &ser_release_list, new: &list);
290 spin_unlock(lock: &ser_lock);
291
292 if (!list_empty(head: &list)) {
293 rtnl_lock();
294 list_for_each_entry_safe(ser, tmp, &list, node) {
295 dev_close(dev: ser->dev);
296 unregister_netdevice(dev: ser->dev);
297 debugfs_deinit(ser);
298 }
299 rtnl_unlock();
300 }
301}
302
303static DECLARE_WORK(ser_release_work, ser_release);
304
305static int ldisc_open(struct tty_struct *tty)
306{
307 struct ser_device *ser;
308 struct net_device *dev;
309 char name[64];
310 int result;
311
312 /* No write no play */
313 if (tty->ops->write == NULL)
314 return -EOPNOTSUPP;
315 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
316 return -EPERM;
317
318 /* release devices to avoid name collision */
319 ser_release(NULL);
320
321 result = snprintf(buf: name, size: sizeof(name), fmt: "cf%s", tty->name);
322 if (result >= IFNAMSIZ)
323 return -EINVAL;
324 dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
325 caifdev_setup);
326 if (!dev)
327 return -ENOMEM;
328
329 ser = netdev_priv(dev);
330 ser->tty = tty_kref_get(tty);
331 ser->dev = dev;
332 debugfs_init(ser, tty);
333 tty->receive_room = 4096;
334 tty->disc_data = ser;
335 set_bit(nr: TTY_DO_WRITE_WAKEUP, addr: &tty->flags);
336 rtnl_lock();
337 result = register_netdevice(dev);
338 if (result) {
339 tty_kref_put(tty);
340 rtnl_unlock();
341 free_netdev(dev);
342 return -ENODEV;
343 }
344
345 spin_lock(lock: &ser_lock);
346 list_add(new: &ser->node, head: &ser_list);
347 spin_unlock(lock: &ser_lock);
348 rtnl_unlock();
349 netif_stop_queue(dev);
350 update_tty_status(ser);
351 return 0;
352}
353
354static void ldisc_close(struct tty_struct *tty)
355{
356 struct ser_device *ser = tty->disc_data;
357
358 tty_kref_put(tty: ser->tty);
359
360 spin_lock(lock: &ser_lock);
361 list_move(list: &ser->node, head: &ser_release_list);
362 spin_unlock(lock: &ser_lock);
363 schedule_work(work: &ser_release_work);
364}
365
366/* The line discipline structure. */
367static struct tty_ldisc_ops caif_ldisc = {
368 .owner = THIS_MODULE,
369 .num = N_CAIF,
370 .name = "n_caif",
371 .open = ldisc_open,
372 .close = ldisc_close,
373 .receive_buf = ldisc_receive,
374 .write_wakeup = ldisc_tx_wakeup
375};
376
377static const struct net_device_ops netdev_ops = {
378 .ndo_open = caif_net_open,
379 .ndo_stop = caif_net_close,
380 .ndo_start_xmit = caif_xmit
381};
382
383static void caifdev_setup(struct net_device *dev)
384{
385 struct ser_device *serdev = netdev_priv(dev);
386
387 dev->features = 0;
388 dev->netdev_ops = &netdev_ops;
389 dev->type = ARPHRD_CAIF;
390 dev->flags = IFF_POINTOPOINT | IFF_NOARP;
391 dev->mtu = CAIF_MAX_MTU;
392 dev->priv_flags |= IFF_NO_QUEUE;
393 dev->needs_free_netdev = true;
394 skb_queue_head_init(list: &serdev->head);
395 serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
396 serdev->common.use_frag = true;
397 serdev->common.use_stx = ser_use_stx;
398 serdev->common.use_fcs = ser_use_fcs;
399 serdev->dev = dev;
400}
401
402
403static int caif_net_open(struct net_device *dev)
404{
405 netif_wake_queue(dev);
406 return 0;
407}
408
409static int caif_net_close(struct net_device *dev)
410{
411 netif_stop_queue(dev);
412 return 0;
413}
414
415static int __init caif_ser_init(void)
416{
417 int ret;
418
419 ret = tty_register_ldisc(new_ldisc: &caif_ldisc);
420 if (ret < 0)
421 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF, ret);
422
423 debugfsdir = debugfs_create_dir(name: "caif_serial", NULL);
424 return ret;
425}
426
427static void __exit caif_ser_exit(void)
428{
429 spin_lock(lock: &ser_lock);
430 list_splice(list: &ser_list, head: &ser_release_list);
431 spin_unlock(lock: &ser_lock);
432 ser_release(NULL);
433 cancel_work_sync(work: &ser_release_work);
434 tty_unregister_ldisc(ldisc: &caif_ldisc);
435 debugfs_remove_recursive(dentry: debugfsdir);
436}
437
438module_init(caif_ser_init);
439module_exit(caif_ser_exit);
440

source code of linux/drivers/net/caif/caif_serial.c