caif_serial.c

  1 /*
  2  * Copyright (C) ST-Ericsson AB 2010
  3  * Author:      Sjur Brendeland / sjur.brandeland@stericsson.com
  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<sjur.brandeland@stericsson.com>");
 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 /*This list is protected by the rtnl lock. */
 39 static LIST_HEAD(ser_list);
 40 
 41 static bool ser_loop;
 42 module_param(ser_loop, bool, S_IRUGO);
 43 MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
 44 
 45 static bool ser_use_stx = true;
 46 module_param(ser_use_stx, bool, S_IRUGO);
 47 MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
 48 
 49 static bool ser_use_fcs = true;
 50 
 51 module_param(ser_use_fcs, bool, S_IRUGO);
 52 MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
 53 
 54 static int ser_write_chunk = MAX_WRITE_CHUNK;
 55 module_param(ser_write_chunk, int, S_IRUGO);
 56 
 57 MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
 58 
 59 static struct dentry *debugfsdir;
 60 
 61 static int caif_net_open(struct net_device *dev);
 62 static int caif_net_close(struct net_device *dev);
 63 
 64 struct ser_device {
 65         struct caif_dev_common common;
 66         struct list_head node;
 67         struct net_device *dev;
 68         struct sk_buff_head head;
 69         struct tty_struct *tty;
 70         bool tx_started;
 71         unsigned long state;
 72         char *tty_name;
 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->hw_stopped << 4 |
 92                 ser->tty->flow_stopped << 3 |
 93                 ser->tty->packet << 2 |
 94                 ser->tty->port->low_latency << 1 |
 95                 ser->tty->warned;
 96 }
 97 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
 98 {
 99         ser->debugfs_tty_dir =
100                         debugfs_create_dir(tty->name, debugfsdir);
101         if (!IS_ERR(ser->debugfs_tty_dir)) {
102                 debugfs_create_blob("last_tx_msg", S_IRUSR,
103                                 ser->debugfs_tty_dir,
104                                 &ser->tx_blob);
105 
106                 debugfs_create_blob("last_rx_msg", S_IRUSR,
107                                 ser->debugfs_tty_dir,
108                                 &ser->rx_blob);
109 
110                 debugfs_create_x32("ser_state", S_IRUSR,
111                                 ser->debugfs_tty_dir,
112                                 (u32 *)&ser->state);
113 
114                 debugfs_create_x8("tty_status", S_IRUSR,
115                                 ser->debugfs_tty_dir,
116                                 &ser->tty_status);
117 
118         }
119         ser->tx_blob.data = ser->tx_data;
120         ser->tx_blob.size = 0;
121         ser->rx_blob.data = ser->rx_data;
122         ser->rx_blob.size = 0;
123 }
124 
125 static inline void debugfs_deinit(struct ser_device *ser)
126 {
127         debugfs_remove_recursive(ser->debugfs_tty_dir);
128 }
129 
130 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
131 {
132         if (size > sizeof(ser->rx_data))
133                 size = sizeof(ser->rx_data);
134         memcpy(ser->rx_data, data, size);
135         ser->rx_blob.data = ser->rx_data;
136         ser->rx_blob.size = size;
137 }
138 
139 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
140 {
141         if (size > sizeof(ser->tx_data))
142                 size = sizeof(ser->tx_data);
143         memcpy(ser->tx_data, data, size);
144         ser->tx_blob.data = ser->tx_data;
145         ser->tx_blob.size = size;
146 }
147 #else
148 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
149 {
150 }
151 
152 static inline void debugfs_deinit(struct ser_device *ser)
153 {
154 }
155 
156 static inline void update_tty_status(struct ser_device *ser)
157 {
158 }
159 
160 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
161 {
162 }
163 
164 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
165 {
166 }
167 
168 #endif
169 
170 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
171                         char *flags, int count)
172 {
173         struct sk_buff *skb = NULL;
174         struct ser_device *ser;
175         int ret;
176         u8 *p;
177 
178         ser = tty->disc_data;
179 
180         /*
181          * NOTE: flags may contain information about break or overrun.
182          * This is not yet handled.
183          */
184 
185 
186         /*
187          * Workaround for garbage at start of transmission,
188          * only enable if STX handling is not enabled.
189          */
190         if (!ser->common.use_stx && !ser->tx_started) {
191                 dev_info(&ser->dev->dev,
192                         "Bytes received before initial transmission -"
193                         "bytes discarded.\n");
194                 return;
195         }
196 
197         BUG_ON(ser->dev == NULL);
198 
199         /* Get a suitable caif packet and copy in data. */
200         skb = netdev_alloc_skb(ser->dev, count+1);
201         if (skb == NULL)
202                 return;
203         p = skb_put(skb, count);
204         memcpy(p, data, count);
205 
206         skb->protocol = htons(ETH_P_CAIF);
207         skb_reset_mac_header(skb);
208         skb->dev = ser->dev;
209         debugfs_rx(ser, data, count);
210         /* Push received packet up the stack. */
211         ret = netif_rx_ni(skb);
212         if (!ret) {
213                 ser->dev->stats.rx_packets++;
214                 ser->dev->stats.rx_bytes += count;
215         } else
216                 ++ser->dev->stats.rx_dropped;
217         update_tty_status(ser);
218 }
219 
220 static int handle_tx(struct ser_device *ser)
221 {
222         struct tty_struct *tty;
223         struct sk_buff *skb;
224         int tty_wr, len, room;
225 
226         tty = ser->tty;
227         ser->tx_started = true;
228 
229         /* Enter critical section */
230         if (test_and_set_bit(CAIF_SENDING, &ser->state))
231                 return 0;
232 
233         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
234         while ((skb = skb_peek(&ser->head)) != NULL) {
235 
236                 /* Make sure you don't write too much */
237                 len = skb->len;
238                 room = tty_write_room(tty);
239                 if (!room)
240                         break;
241                 if (room > ser_write_chunk)
242                         room = ser_write_chunk;
243                 if (len > room)
244                         len = room;
245 
246                 /* Write to tty or loopback */
247                 if (!ser_loop) {
248                         tty_wr = tty->ops->write(tty, skb->data, len);
249                         update_tty_status(ser);
250                 } else {
251                         tty_wr = len;
252                         ldisc_receive(tty, skb->data, NULL, len);
253                 }
254                 ser->dev->stats.tx_packets++;
255                 ser->dev->stats.tx_bytes += tty_wr;
256 
257                 /* Error on TTY ?! */
258                 if (tty_wr < 0)
259                         goto error;
260                 /* Reduce buffer written, and discard if empty */
261                 skb_pull(skb, tty_wr);
262                 if (skb->len == 0) {
263                         struct sk_buff *tmp = skb_dequeue(&ser->head);
264                         WARN_ON(tmp != skb);
265                         if (in_interrupt())
266                                 dev_kfree_skb_irq(skb);
267                         else
268                                 kfree_skb(skb);
269                 }
270         }
271         /* Send flow off if queue is empty */
272         if (ser->head.qlen <= SEND_QUEUE_LOW &&
273                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
274                 ser->common.flowctrl != NULL)
275                                 ser->common.flowctrl(ser->dev, ON);
276         clear_bit(CAIF_SENDING, &ser->state);
277         return 0;
278 error:
279         clear_bit(CAIF_SENDING, &ser->state);
280         return tty_wr;
281 }
282 
283 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
284 {
285         struct ser_device *ser;
286 
287         BUG_ON(dev == NULL);
288         ser = netdev_priv(dev);
289 
290         /* Send flow off once, on high water mark */
291         if (ser->head.qlen > SEND_QUEUE_HIGH &&
292                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
293                 ser->common.flowctrl != NULL)
294 
295                 ser->common.flowctrl(ser->dev, OFF);
296 
297         skb_queue_tail(&ser->head, skb);
298         return handle_tx(ser);
299 }
300 
301 
302 static void ldisc_tx_wakeup(struct tty_struct *tty)
303 {
304         struct ser_device *ser;
305 
306         ser = tty->disc_data;
307         BUG_ON(ser == NULL);
308         WARN_ON(ser->tty != tty);
309         handle_tx(ser);
310 }
311 
312 
313 static int ldisc_open(struct tty_struct *tty)
314 {
315         struct ser_device *ser;
316         struct net_device *dev;
317         char name[64];
318         int result;
319 
320         /* No write no play */
321         if (tty->ops->write == NULL)
322                 return -EOPNOTSUPP;
323         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
324                 return -EPERM;
325 
326         sprintf(name, "cf%s", tty->name);
327         dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
328         if (!dev)
329                 return -ENOMEM;
330 
331         ser = netdev_priv(dev);
332         ser->tty = tty_kref_get(tty);
333         ser->dev = dev;
334         debugfs_init(ser, tty);
335         tty->receive_room = N_TTY_BUF_SIZE;
336         tty->disc_data = ser;
337         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
338         rtnl_lock();
339         result = register_netdevice(dev);
340         if (result) {
341                 rtnl_unlock();
342                 free_netdev(dev);
343                 return -ENODEV;
344         }
345 
346         list_add(&ser->node, &ser_list);
347         rtnl_unlock();
348         netif_stop_queue(dev);
349         update_tty_status(ser);
350         return 0;
351 }
352 
353 static void ldisc_close(struct tty_struct *tty)
354 {
355         struct ser_device *ser = tty->disc_data;
356         /* Remove may be called inside or outside of rtnl_lock */
357         int islocked = rtnl_is_locked();
358 
359         if (!islocked)
360                 rtnl_lock();
361         /* device is freed automagically by net-sysfs */
362         dev_close(ser->dev);
363         unregister_netdevice(ser->dev);
364         list_del(&ser->node);
365         debugfs_deinit(ser);
366         tty_kref_put(ser->tty);
367         if (!islocked)
368                 rtnl_unlock();
369 }
370 
371 /* The line discipline structure. */
372 static struct tty_ldisc_ops caif_ldisc = {
373         .owner =        THIS_MODULE,
374         .magic =        TTY_LDISC_MAGIC,
375         .name =         "n_caif",
376         .open =         ldisc_open,
377         .close =        ldisc_close,
378         .receive_buf =  ldisc_receive,
379         .write_wakeup = ldisc_tx_wakeup
380 };
381 
382 static int register_ldisc(void)
383 {
384         int result;
385 
386         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
387         if (result < 0) {
388                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
389                         result);
390                 return result;
391         }
392         return result;
393 }
394 static const struct net_device_ops netdev_ops = {
395         .ndo_open = caif_net_open,
396         .ndo_stop = caif_net_close,
397         .ndo_start_xmit = caif_xmit
398 };
399 
400 static void caifdev_setup(struct net_device *dev)
401 {
402         struct ser_device *serdev = netdev_priv(dev);
403 
404         dev->features = 0;
405         dev->netdev_ops = &netdev_ops;
406         dev->type = ARPHRD_CAIF;
407         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
408         dev->mtu = CAIF_MAX_MTU;
409         dev->tx_queue_len = 0;
410         dev->destructor = free_netdev;
411         skb_queue_head_init(&serdev->head);
412         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
413         serdev->common.use_frag = true;
414         serdev->common.use_stx = ser_use_stx;
415         serdev->common.use_fcs = ser_use_fcs;
416         serdev->dev = dev;
417 }
418 
419 
420 static int caif_net_open(struct net_device *dev)
421 {
422         netif_wake_queue(dev);
423         return 0;
424 }
425 
426 static int caif_net_close(struct net_device *dev)
427 {
428         netif_stop_queue(dev);
429         return 0;
430 }
431 
432 static int __init caif_ser_init(void)
433 {
434         int ret;
435 
436         ret = register_ldisc();
437         debugfsdir = debugfs_create_dir("caif_serial", NULL);
438         return ret;
439 }
440 
441 static void __exit caif_ser_exit(void)
442 {
443         struct ser_device *ser = NULL;
444         struct list_head *node;
445         struct list_head *_tmp;
446 
447         list_for_each_safe(node, _tmp, &ser_list) {
448                 ser = list_entry(node, struct ser_device, node);
449                 dev_close(ser->dev);
450                 unregister_netdevice(ser->dev);
451                 list_del(node);
452         }
453         tty_unregister_ldisc(N_CAIF);
454         debugfs_remove_recursive(debugfsdir);
455 }
456 
457 module_init(caif_ser_init);
458 module_exit(caif_ser_exit);
459
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Linux/drivers/net/caif/caif_serial.c
