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         debugfs_rx(ser, data, count);
 208         /* Push received packet up the stack. */
 209         ret = netif_rx_ni(skb);
 210         if (!ret) {
 211                 ser->dev->stats.rx_packets++;
 212                 ser->dev->stats.rx_bytes += count;
 213         } else
 214                 ++ser->dev->stats.rx_dropped;
 215         update_tty_status(ser);
 216 }
 217
 218 static int handle_tx(struct ser_device *ser)
 219 {
 220         struct tty_struct *tty;
 221         struct sk_buff *skb;
 222         int tty_wr, len, room;
 223
 224         tty = ser->tty;
 225         ser->tx_started = true;
 226
 227         /* Enter critical section */
 228         if (test_and_set_bit(CAIF_SENDING, &ser->state))
 229                 return 0;
 230
 231         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
 232         while ((skb = skb_peek(&ser->head)) != NULL) {
 233
 234                 /* Make sure you don't write too much */
 235                 len = skb->len;
 236                 room = tty_write_room(tty);
 237                 if (!room)
 238                         break;
 239                 if (room > ser_write_chunk)
 240                         room = ser_write_chunk;
 241                 if (len > room)
 242                         len = room;
 243
 244                 /* Write to tty or loopback */
 245                 if (!ser_loop) {
 246                         tty_wr = tty->ops->write(tty, skb->data, len);
 247                         update_tty_status(ser);
 248                 } else {
 249                         tty_wr = len;
 250                         ldisc_receive(tty, skb->data, NULL, len);
 251                 }
 252                 ser->dev->stats.tx_packets++;
 253                 ser->dev->stats.tx_bytes += tty_wr;
 254
 255                 /* Error on TTY ?! */
 256                 if (tty_wr < 0)
 257                         goto error;
 258                 /* Reduce buffer written, and discard if empty */
 259                 skb_pull(skb, tty_wr);
 260                 if (skb->len == 0) {
 261                         struct sk_buff *tmp = skb_dequeue(&ser->head);
 262                         WARN_ON(tmp != skb);
 263                         if (in_interrupt())
 264                                 dev_kfree_skb_irq(skb);
 265                         else
 266                                 kfree_skb(skb);
 267                 }
 268         }
 269         /* Send flow off if queue is empty */
 270         if (ser->head.qlen <= SEND_QUEUE_LOW &&
 271                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 272                 ser->common.flowctrl != NULL)
 273                                 ser->common.flowctrl(ser->dev, ON);
 274         clear_bit(CAIF_SENDING, &ser->state);
 275         return 0;
 276 error:
 277         clear_bit(CAIF_SENDING, &ser->state);
 278         return tty_wr;
 279 }
 280
 281 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
 282 {
 283         struct ser_device *ser;
 284
 285         BUG_ON(dev == NULL);
 286         ser = netdev_priv(dev);
 287
 288         /* Send flow off once, on high water mark */
 289         if (ser->head.qlen > SEND_QUEUE_HIGH &&
 290                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 291                 ser->common.flowctrl != NULL)
 292
 293                 ser->common.flowctrl(ser->dev, OFF);
 294
 295         skb_queue_tail(&ser->head, skb);
 296         return handle_tx(ser);
 297 }
 298
 299
 300 static void ldisc_tx_wakeup(struct tty_struct *tty)
 301 {
 302         struct ser_device *ser;
 303
 304         ser = tty->disc_data;
 305         BUG_ON(ser == NULL);
 306         WARN_ON(ser->tty != tty);
 307         handle_tx(ser);
 308 }
 309
 310
 311 static void ser_release(struct work_struct *work)
 312 {
 313         struct list_head list;
 314         struct ser_device *ser, *tmp;
 315
 316         spin_lock(&ser_lock);
 317         list_replace_init(&ser_release_list, &list);
 318         spin_unlock(&ser_lock);
 319
 320         if (!list_empty(&list)) {
 321                 rtnl_lock();
 322                 list_for_each_entry_safe(ser, tmp, &list, node) {
 323                         dev_close(ser->dev);
 324                         unregister_netdevice(ser->dev);
 325                         debugfs_deinit(ser);
 326                 }
 327                 rtnl_unlock();
 328         }
 329 }
 330
 331 static DECLARE_WORK(ser_release_work, ser_release);
 332
 333 static int ldisc_open(struct tty_struct *tty)
 334 {
 335         struct ser_device *ser;
 336         struct net_device *dev;
 337         char name[64];
 338         int result;
 339
 340         /* No write no play */
 341         if (tty->ops->write == NULL)
 342                 return -EOPNOTSUPP;
 343         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
 344                 return -EPERM;
 345
 346         /* release devices to avoid name collision */
 347         ser_release(NULL);
 348
 349         result = snprintf(name, sizeof(name), "cf%s", tty->name);
 350         if (result >= IFNAMSIZ)
 351                 return -EINVAL;
 352         dev = alloc_netdev(sizeof(*ser), name, 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);