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_data(skb, data, count);
 202
 203         skb->protocol = htons(ETH_P_CAIF);
 204         skb_reset_mac_header(skb);
 205         debugfs_rx(ser, data, count);
 206         /* Push received packet up the stack. */
 207         ret = netif_rx_ni(skb);
 208         if (!ret) {
 209                 ser->dev->stats.rx_packets++;
 210                 ser->dev->stats.rx_bytes += count;
 211         } else
 212                 ++ser->dev->stats.rx_dropped;
 213         update_tty_status(ser);
 214 }
 215
 216 static int handle_tx(struct ser_device *ser)
 217 {
 218         struct tty_struct *tty;
 219         struct sk_buff *skb;
 220         int tty_wr, len, room;
 221
 222         tty = ser->tty;
 223         ser->tx_started = true;
 224
 225         /* Enter critical section */
 226         if (test_and_set_bit(CAIF_SENDING, &ser->state))
 227                 return 0;
 228
 229         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
 230         while ((skb = skb_peek(&ser->head)) != NULL) {
 231
 232                 /* Make sure you don't write too much */
 233                 len = skb->len;
 234                 room = tty_write_room(tty);
 235                 if (!room)
 236                         break;
 237                 if (room > ser_write_chunk)
 238                         room = ser_write_chunk;
 239                 if (len > room)
 240                         len = room;
 241
 242                 /* Write to tty or loopback */
 243                 if (!ser_loop) {
 244                         tty_wr = tty->ops->write(tty, skb->data, len);
 245                         update_tty_status(ser);
 246                 } else {
 247                         tty_wr = len;
 248                         ldisc_receive(tty, skb->data, NULL, len);
 249                 }
 250                 ser->dev->stats.tx_packets++;
 251                 ser->dev->stats.tx_bytes += tty_wr;
 252
 253                 /* Error on TTY ?! */
 254                 if (tty_wr < 0)
 255                         goto error;
 256                 /* Reduce buffer written, and discard if empty */
 257                 skb_pull(skb, tty_wr);
 258                 if (skb->len == 0) {
 259                         struct sk_buff *tmp = skb_dequeue(&ser->head);
 260                         WARN_ON(tmp != skb);
 261                         if (in_interrupt())
 262                                 dev_kfree_skb_irq(skb);
 263                         else
 264                                 kfree_skb(skb);
 265                 }
 266         }
 267         /* Send flow off if queue is empty */
 268         if (ser->head.qlen <= SEND_QUEUE_LOW &&
 269                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 270                 ser->common.flowctrl != NULL)
 271                                 ser->common.flowctrl(ser->dev, ON);
 272         clear_bit(CAIF_SENDING, &ser->state);
 273         return 0;
 274 error:
 275         clear_bit(CAIF_SENDING, &ser->state);
 276         return tty_wr;
 277 }
 278
 279 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
 280 {
 281         struct ser_device *ser;
 282
 283         BUG_ON(dev == NULL);
 284         ser = netdev_priv(dev);
 285
 286         /* Send flow off once, on high water mark */
 287         if (ser->head.qlen > SEND_QUEUE_HIGH &&
 288                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 289                 ser->common.flowctrl != NULL)
 290
 291                 ser->common.flowctrl(ser->dev, OFF);
 292
 293         skb_queue_tail(&ser->head, skb);
 294         return handle_tx(ser);
 295 }
 296
 297
 298 static void ldisc_tx_wakeup(struct tty_struct *tty)
 299 {
 300         struct ser_device *ser;
 301
 302         ser = tty->disc_data;
 303         BUG_ON(ser == NULL);
 304         WARN_ON(ser->tty != tty);
 305         handle_tx(ser);
 306 }
 307
 308
 309 static void ser_release(struct work_struct *work)
 310 {
 311         struct list_head list;
 312         struct ser_device *ser, *tmp;
 313
 314         spin_lock(&ser_lock);
 315         list_replace_init(&ser_release_list, &list);
 316         spin_unlock(&ser_lock);
 317
 318         if (!list_empty(&list)) {
 319                 rtnl_lock();
 320                 list_for_each_entry_safe(ser, tmp, &list, node) {
 321                         dev_close(ser->dev);
 322                         unregister_netdevice(ser->dev);
 323                         debugfs_deinit(ser);
 324                 }
 325                 rtnl_unlock();
 326         }
 327 }
 328
 329 static DECLARE_WORK(ser_release_work, ser_release);
 330
 331 static int ldisc_open(struct tty_struct *tty)
 332 {
 333         struct ser_device *ser;
 334         struct net_device *dev;
 335         char name[64];
 336         int result;
 337
 338         /* No write no play */
 339         if (tty->ops->write == NULL)
 340                 return -EOPNOTSUPP;
 341         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
 342                 return -EPERM;
 343
 344         /* release devices to avoid name collision */
 345         ser_release(NULL);
 346
 347         result = snprintf(name, sizeof(name), "cf%s", tty->name);
 348         if (result >= IFNAMSIZ)
 349                 return -EINVAL;
 350         dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
 351                            caifdev_setup);
 352         if (!dev)
 353                 return -ENOMEM;
 354
 355         ser = netdev_priv(dev);
 356         ser->tty = tty_kref_get(tty);
 357         ser->dev = dev;
 358         debugfs_init(ser, tty);
 359         tty->receive_room = N_TTY_BUF_SIZE;
 360         tty->disc_data = ser;
 361         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 362         rtnl_lock();
 363         result = register_netdevice(dev);
 364         if (result) {
 365                 rtnl_unlock();
 366                 free_netdev(dev);
 367                 return -ENODEV;
 368         }
 369
 370         spin_lock(&ser_lock);
 371         list_add(&ser->node, &ser_list);
 372         spin_unlock(&ser_lock);
 373         rtnl_unlock();
 374         netif_stop_queue(dev);
 375         update_tty_status(ser);
 376         return 0;
 377 }
 378
 379 static void ldisc_close(struct tty_struct *tty)
 380 {
 381         struct ser_device *ser = tty->disc_data;
 382
 383         tty_kref_put(ser->tty);
 384
 385         spin_lock(&ser_lock);
 386         list_move(&ser->node, &ser_release_list);
 387         spin_unlock(&ser_lock);
 388         schedule_work(&ser_release_work);
 389 }
 390
 391 /* The line discipline structure. */
 392 static struct tty_ldisc_ops caif_ldisc = {
 393         .owner =        THIS_MODULE,
 394         .magic =        TTY_LDISC_MAGIC,
 395         .name =         "n_caif",
 396         .open =         ldisc_open,
 397         .close =        ldisc_close,
 398         .receive_buf =  ldisc_receive,
 399         .write_wakeup = ldisc_tx_wakeup
 400 };
 401
 402 static int register_ldisc(void)
 403 {
 404         int result;
 405
 406         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
 407         if (result < 0) {
 408                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
 409                         result);
 410                 return result;
 411         }
 412         return result;
 413 }
 414 static const struct net_device_ops netdev_ops = {
 415         .ndo_open = caif_net_open,
 416         .ndo_stop = caif_net_close,
 417         .ndo_start_xmit = caif_xmit
 418 };
 419
 420 static void caifdev_setup(struct net_device *dev)
 421 {
 422         struct ser_device *serdev = netdev_priv(dev);
 423
 424         dev->features = 0;
 425         dev->netdev_ops = &netdev_ops;
 426         dev->type = ARPHRD_CAIF;
 427         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
 428         dev->mtu = CAIF_MAX_MTU;
 429         dev->priv_flags |= IFF_NO_QUEUE;
 430         dev->needs_free_netdev = true;
 431         skb_queue_head_init(&serdev->head);
 432         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
 433         serdev->common.use_frag = true;
 434         serdev->common.use_stx = ser_use_stx;
 435         serdev->common.use_fcs = ser_use_fcs;
 436         serdev->dev = dev;
 437 }
 438
 439
 440 static int caif_net_open(struct net_device *dev)
 441 {
 442         netif_wake_queue(dev);
 443         return 0;
 444 }
 445
 446 static int caif_net_close(struct net_device *dev)
 447 {
 448         netif_stop_queue(dev);
 449         return 0;
 450 }
 451
 452 static int __init caif_ser_init(void)
 453 {
 454         int ret;
 455
 456         ret = register_ldisc();
 457         debugfsdir = debugfs_create_dir("caif_serial", NULL);
 458         return ret;
 459 }
 460
 461 static void __exit caif_ser_exit(void)
 462 {
 463         spin_lock(&ser_lock);
 464         list_splice(&ser_list, &ser_release_list);
 465         spin_unlock(&ser_lock);
 466         ser_release(NULL);
 467         cancel_work_sync(&ser_release_work);
 468         tty_unregister_ldisc(N_CAIF);
 469         debugfs_remove_recursive(debugfsdir);
 470 }
 471
 472 module_init(caif_ser_init);
 473 module_exit(caif_ser_exit);