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

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