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Linux/drivers/net/caif/caif_serial.c

  1 /*
  2  * Copyright (C) ST-Ericsson AB 2010
  3  * Author:      Sjur Brendeland
  4  * License terms: GNU General Public License (GPL) version 2
  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, S_IRUGO);
 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, S_IRUGO);
 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, S_IRUGO);
 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, S_IRUGO);
 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         char *tty_name;
 74 #ifdef CONFIG_DEBUG_FS
 75         struct dentry *debugfs_tty_dir;
 76         struct debugfs_blob_wrapper tx_blob;
 77         struct debugfs_blob_wrapper rx_blob;
 78         u8 rx_data[128];
 79         u8 tx_data[128];
 80         u8 tty_status;
 81 
 82 #endif
 83 };
 84 
 85 static void caifdev_setup(struct net_device *dev);
 86 static void ldisc_tx_wakeup(struct tty_struct *tty);
 87 #ifdef CONFIG_DEBUG_FS
 88 static inline void update_tty_status(struct ser_device *ser)
 89 {
 90         ser->tty_status =
 91                 ser->tty->stopped << 5 |
 92                 ser->tty->flow_stopped << 3 |
 93                 ser->tty->packet << 2 |
 94                 ser->tty->port->low_latency << 1;
 95 }
 96 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
 97 {
 98         ser->debugfs_tty_dir =
 99                         debugfs_create_dir(tty->name, debugfsdir);
100         if (!IS_ERR(ser->debugfs_tty_dir)) {
101                 debugfs_create_blob("last_tx_msg", S_IRUSR,
102                                 ser->debugfs_tty_dir,
103                                 &ser->tx_blob);
104 
105                 debugfs_create_blob("last_rx_msg", S_IRUSR,
106                                 ser->debugfs_tty_dir,
107                                 &ser->rx_blob);
108 
109                 debugfs_create_x32("ser_state", S_IRUSR,
110                                 ser->debugfs_tty_dir,
111                                 (u32 *)&ser->state);
112 
113                 debugfs_create_x8("tty_status", S_IRUSR,
114                                 ser->debugfs_tty_dir,
115                                 &ser->tty_status);
116 
117         }
118         ser->tx_blob.data = ser->tx_data;
119         ser->tx_blob.size = 0;
120         ser->rx_blob.data = ser->rx_data;
121         ser->rx_blob.size = 0;
122 }
123 
124 static inline void debugfs_deinit(struct ser_device *ser)
125 {
126         debugfs_remove_recursive(ser->debugfs_tty_dir);
127 }
128 
129 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
130 {
131         if (size > sizeof(ser->rx_data))
132                 size = sizeof(ser->rx_data);
133         memcpy(ser->rx_data, data, size);
134         ser->rx_blob.data = ser->rx_data;
135         ser->rx_blob.size = size;
136 }
137 
138 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
139 {
140         if (size > sizeof(ser->tx_data))
141                 size = sizeof(ser->tx_data);
142         memcpy(ser->tx_data, data, size);
143         ser->tx_blob.data = ser->tx_data;
144         ser->tx_blob.size = size;
145 }
146 #else
147 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
148 {
149 }
150 
151 static inline void debugfs_deinit(struct ser_device *ser)
152 {
153 }
154 
155 static inline void update_tty_status(struct ser_device *ser)
156 {
157 }
158 
159 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
160 {
161 }
162 
163 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
164 {
165 }
166 
167 #endif
168 
169 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
170                         char *flags, int count)
171 {
172         struct sk_buff *skb = NULL;
173         struct ser_device *ser;
174         int ret;
175         u8 *p;
176 
177         ser = tty->disc_data;
178 
179         /*
180          * NOTE: flags may contain information about break or overrun.
181          * This is not yet handled.
182          */
183 
184 
185         /*
186          * Workaround for garbage at start of transmission,
187          * only enable if STX handling is not enabled.
188          */
189         if (!ser->common.use_stx && !ser->tx_started) {
190                 dev_info(&ser->dev->dev,
191                         "Bytes received before initial transmission -"
192                         "bytes discarded.\n");
193                 return;
194         }
195 
196         BUG_ON(ser->dev == NULL);
197 
198         /* Get a suitable caif packet and copy in data. */
199         skb = netdev_alloc_skb(ser->dev, count+1);
200         if (skb == NULL)
201                 return;
202         p = skb_put(skb, count);
203         memcpy(p, data, count);
204 
205         skb->protocol = htons(ETH_P_CAIF);
206         skb_reset_mac_header(skb);
207         skb->dev = ser->dev;
208         debugfs_rx(ser, data, count);
209         /* Push received packet up the stack. */
210         ret = netif_rx_ni(skb);
211         if (!ret) {
212                 ser->dev->stats.rx_packets++;
213                 ser->dev->stats.rx_bytes += count;
214         } else
215                 ++ser->dev->stats.rx_dropped;
216         update_tty_status(ser);
217 }
218 
219 static int handle_tx(struct ser_device *ser)
220 {
221         struct tty_struct *tty;
222         struct sk_buff *skb;
223         int tty_wr, len, room;
224 
225         tty = ser->tty;
226         ser->tx_started = true;
227 
228         /* Enter critical section */
229         if (test_and_set_bit(CAIF_SENDING, &ser->state))
230                 return 0;
231 
232         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
233         while ((skb = skb_peek(&ser->head)) != NULL) {
234 
235                 /* Make sure you don't write too much */
236                 len = skb->len;
237                 room = tty_write_room(tty);
238                 if (!room)
239                         break;
240                 if (room > ser_write_chunk)
241                         room = ser_write_chunk;
242                 if (len > room)
243                         len = room;
244 
245                 /* Write to tty or loopback */
246                 if (!ser_loop) {
247                         tty_wr = tty->ops->write(tty, skb->data, len);
248                         update_tty_status(ser);
249                 } else {
250                         tty_wr = len;
251                         ldisc_receive(tty, skb->data, NULL, len);
252                 }
253                 ser->dev->stats.tx_packets++;
254                 ser->dev->stats.tx_bytes += tty_wr;
255 
256                 /* Error on TTY ?! */
257                 if (tty_wr < 0)
258                         goto error;
259                 /* Reduce buffer written, and discard if empty */
260                 skb_pull(skb, tty_wr);
261                 if (skb->len == 0) {
262                         struct sk_buff *tmp = skb_dequeue(&ser->head);
263                         WARN_ON(tmp != skb);
264                         if (in_interrupt())
265                                 dev_kfree_skb_irq(skb);
266                         else
267                                 kfree_skb(skb);
268                 }
269         }
270         /* Send flow off if queue is empty */
271         if (ser->head.qlen <= SEND_QUEUE_LOW &&
272                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
273                 ser->common.flowctrl != NULL)
274                                 ser->common.flowctrl(ser->dev, ON);
275         clear_bit(CAIF_SENDING, &ser->state);
276         return 0;
277 error:
278         clear_bit(CAIF_SENDING, &ser->state);
279         return tty_wr;
280 }
281 
282 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
283 {
284         struct ser_device *ser;
285 
286         BUG_ON(dev == NULL);
287         ser = netdev_priv(dev);
288 
289         /* Send flow off once, on high water mark */
290         if (ser->head.qlen > SEND_QUEUE_HIGH &&
291                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
292                 ser->common.flowctrl != NULL)
293 
294                 ser->common.flowctrl(ser->dev, OFF);
295 
296         skb_queue_tail(&ser->head, skb);
297         return handle_tx(ser);
298 }
299 
300 
301 static void ldisc_tx_wakeup(struct tty_struct *tty)
302 {
303         struct ser_device *ser;
304 
305         ser = tty->disc_data;
306         BUG_ON(ser == NULL);
307         WARN_ON(ser->tty != tty);
308         handle_tx(ser);
309 }
310 
311 
312 static void ser_release(struct work_struct *work)
313 {
314         struct list_head list;
315         struct ser_device *ser, *tmp;
316 
317         spin_lock(&ser_lock);
318         list_replace_init(&ser_release_list, &list);
319         spin_unlock(&ser_lock);
320 
321         if (!list_empty(&list)) {
322                 rtnl_lock();
323                 list_for_each_entry_safe(ser, tmp, &list, node) {
324                         dev_close(ser->dev);
325                         unregister_netdevice(ser->dev);
326                         debugfs_deinit(ser);
327                 }
328                 rtnl_unlock();
329         }
330 }
331 
332 static DECLARE_WORK(ser_release_work, ser_release);
333 
334 static int ldisc_open(struct tty_struct *tty)
335 {
336         struct ser_device *ser;
337         struct net_device *dev;
338         char name[64];
339         int result;
340 
341         /* No write no play */
342         if (tty->ops->write == NULL)
343                 return -EOPNOTSUPP;
344         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
345                 return -EPERM;
346 
347         /* release devices to avoid name collision */
348         ser_release(NULL);
349 
350         result = snprintf(name, sizeof(name), "cf%s", tty->name);
351         if (result >= IFNAMSIZ)
352                 return -EINVAL;
353         dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
354         if (!dev)
355                 return -ENOMEM;
356 
357         ser = netdev_priv(dev);
358         ser->tty = tty_kref_get(tty);
359         ser->dev = dev;
360         debugfs_init(ser, tty);
361         tty->receive_room = N_TTY_BUF_SIZE;
362         tty->disc_data = ser;
363         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
364         rtnl_lock();
365         result = register_netdevice(dev);
366         if (result) {
367                 rtnl_unlock();
368                 free_netdev(dev);
369                 return -ENODEV;
370         }
371 
372         spin_lock(&ser_lock);
373         list_add(&ser->node, &ser_list);
374         spin_unlock(&ser_lock);
375         rtnl_unlock();
376         netif_stop_queue(dev);
377         update_tty_status(ser);
378         return 0;
379 }
380 
381 static void ldisc_close(struct tty_struct *tty)
382 {
383         struct ser_device *ser = tty->disc_data;
384 
385         tty_kref_put(ser->tty);
386 
387         spin_lock(&ser_lock);
388         list_move(&ser->node, &ser_release_list);
389         spin_unlock(&ser_lock);
390         schedule_work(&ser_release_work);
391 }
392 
393 /* The line discipline structure. */
394 static struct tty_ldisc_ops caif_ldisc = {
395         .owner =        THIS_MODULE,
396         .magic =        TTY_LDISC_MAGIC,
397         .name =         "n_caif",
398         .open =         ldisc_open,
399         .close =        ldisc_close,
400         .receive_buf =  ldisc_receive,
401         .write_wakeup = ldisc_tx_wakeup
402 };
403 
404 static int register_ldisc(void)
405 {
406         int result;
407 
408         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
409         if (result < 0) {
410                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
411                         result);
412                 return result;
413         }
414         return result;
415 }
416 static const struct net_device_ops netdev_ops = {
417         .ndo_open = caif_net_open,
418         .ndo_stop = caif_net_close,
419         .ndo_start_xmit = caif_xmit
420 };
421 
422 static void caifdev_setup(struct net_device *dev)
423 {
424         struct ser_device *serdev = netdev_priv(dev);
425 
426         dev->features = 0;
427         dev->netdev_ops = &netdev_ops;
428         dev->type = ARPHRD_CAIF;
429         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
430         dev->mtu = CAIF_MAX_MTU;
431         dev->tx_queue_len = 0;
432         dev->destructor = free_netdev;
433         skb_queue_head_init(&serdev->head);
434         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
435         serdev->common.use_frag = true;
436         serdev->common.use_stx = ser_use_stx;
437         serdev->common.use_fcs = ser_use_fcs;
438         serdev->dev = dev;
439 }
440 
441 
442 static int caif_net_open(struct net_device *dev)
443 {
444         netif_wake_queue(dev);
445         return 0;
446 }
447 
448 static int caif_net_close(struct net_device *dev)
449 {
450         netif_stop_queue(dev);
451         return 0;
452 }
453 
454 static int __init caif_ser_init(void)
455 {
456         int ret;
457 
458         ret = register_ldisc();
459         debugfsdir = debugfs_create_dir("caif_serial", NULL);
460         return ret;
461 }
462 
463 static void __exit caif_ser_exit(void)
464 {
465         spin_lock(&ser_lock);
466         list_splice(&ser_list, &ser_release_list);
467         spin_unlock(&ser_lock);
468         ser_release(NULL);
469         cancel_work_sync(&ser_release_work);
470         tty_unregister_ldisc(N_CAIF);
471         debugfs_remove_recursive(debugfsdir);
472 }
473 
474 module_init(caif_ser_init);
475 module_exit(caif_ser_exit);
476 

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