drivers/net/caif/caif_serial.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) ST-Ericsson AB 2010
   4  * Author:      Sjur Brendeland
   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, 0444);
  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, 0444);
  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, 0444);
  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, 0444);
  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 = debugfs_create_dir(tty->name, debugfsdir);
  98
  99         debugfs_create_blob("last_tx_msg", 0400, ser->debugfs_tty_dir,
 100                             &ser->tx_blob);
 101
 102         debugfs_create_blob("last_rx_msg", 0400, ser->debugfs_tty_dir,
 103                             &ser->rx_blob);
 104
 105         debugfs_create_xul("ser_state", 0400, ser->debugfs_tty_dir,
 106                            &ser->state);
 107
 108         debugfs_create_x8("tty_status", 0400, ser->debugfs_tty_dir,
 109                           &ser->tty_status);
 110
 111         ser->tx_blob.data = ser->tx_data;
 112         ser->tx_blob.size = 0;
 113         ser->rx_blob.data = ser->rx_data;
 114         ser->rx_blob.size = 0;
 115 }
 116
 117 static inline void debugfs_deinit(struct ser_device *ser)
 118 {
 119         debugfs_remove_recursive(ser->debugfs_tty_dir);
 120 }
 121
 122 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 123 {
 124         if (size > sizeof(ser->rx_data))
 125                 size = sizeof(ser->rx_data);
 126         memcpy(ser->rx_data, data, size);
 127         ser->rx_blob.data = ser->rx_data;
 128         ser->rx_blob.size = size;
 129 }
 130
 131 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 132 {
 133         if (size > sizeof(ser->tx_data))
 134                 size = sizeof(ser->tx_data);
 135         memcpy(ser->tx_data, data, size);
 136         ser->tx_blob.data = ser->tx_data;
 137         ser->tx_blob.size = size;
 138 }
 139 #else
 140 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
 141 {
 142 }
 143
 144 static inline void debugfs_deinit(struct ser_device *ser)
 145 {
 146 }
 147
 148 static inline void update_tty_status(struct ser_device *ser)
 149 {
 150 }
 151
 152 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 153 {
 154 }
 155
 156 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 157 {
 158 }
 159
 160 #endif
 161
 162 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
 163                         char *flags, int count)
 164 {
 165         struct sk_buff *skb = NULL;
 166         struct ser_device *ser;
 167         int ret;
 168
 169         ser = tty->disc_data;
 170
 171         /*
 172          * NOTE: flags may contain information about break or overrun.
 173          * This is not yet handled.
 174          */
 175
 176
 177         /*
 178          * Workaround for garbage at start of transmission,
 179          * only enable if STX handling is not enabled.
 180          */
 181         if (!ser->common.use_stx && !ser->tx_started) {
 182                 dev_info(&ser->dev->dev,
 183                         "Bytes received before initial transmission -"
 184                         "bytes discarded.\n");
 185                 return;
 186         }
 187
 188         BUG_ON(ser->dev == NULL);
 189
 190         /* Get a suitable caif packet and copy in data. */
 191         skb = netdev_alloc_skb(ser->dev, count+1);
 192         if (skb == NULL)
 193                 return;
 194         skb_put_data(skb, data, count);
 195
 196         skb->protocol = htons(ETH_P_CAIF);
 197         skb_reset_mac_header(skb);
 198         debugfs_rx(ser, data, count);
 199         /* Push received packet up the stack. */
 200         ret = netif_rx_ni(skb);
 201         if (!ret) {
 202                 ser->dev->stats.rx_packets++;
 203                 ser->dev->stats.rx_bytes += count;
 204         } else
 205                 ++ser->dev->stats.rx_dropped;
 206         update_tty_status(ser);
 207 }
 208
 209 static int handle_tx(struct ser_device *ser)
 210 {
 211         struct tty_struct *tty;
 212         struct sk_buff *skb;
 213         int tty_wr, len, room;
 214
 215         tty = ser->tty;
 216         ser->tx_started = true;
 217
 218         /* Enter critical section */
 219         if (test_and_set_bit(CAIF_SENDING, &ser->state))
 220                 return 0;
 221
 222         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
 223         while ((skb = skb_peek(&ser->head)) != NULL) {
 224
 225                 /* Make sure you don't write too much */
 226                 len = skb->len;
 227                 room = tty_write_room(tty);
 228                 if (!room)
 229                         break;
 230                 if (room > ser_write_chunk)
 231                         room = ser_write_chunk;
 232                 if (len > room)
 233                         len = room;
 234
 235                 /* Write to tty or loopback */
 236                 if (!ser_loop) {
 237                         tty_wr = tty->ops->write(tty, skb->data, len);
 238                         update_tty_status(ser);
 239                 } else {
 240                         tty_wr = len;
 241                         ldisc_receive(tty, skb->data, NULL, len);
 242                 }
 243                 ser->dev->stats.tx_packets++;
 244                 ser->dev->stats.tx_bytes += tty_wr;
 245
 246                 /* Error on TTY ?! */
 247                 if (tty_wr < 0)
 248                         goto error;
 249                 /* Reduce buffer written, and discard if empty */
 250                 skb_pull(skb, tty_wr);
 251                 if (skb->len == 0) {
 252                         struct sk_buff *tmp = skb_dequeue(&ser->head);
 253                         WARN_ON(tmp != skb);
 254                         dev_consume_skb_any(skb);
 255                 }
 256         }
 257         /* Send flow off if queue is empty */
 258         if (ser->head.qlen <= SEND_QUEUE_LOW &&
 259                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 260                 ser->common.flowctrl != NULL)
 261                                 ser->common.flowctrl(ser->dev, ON);
 262         clear_bit(CAIF_SENDING, &ser->state);
 263         return 0;
 264 error:
 265         clear_bit(CAIF_SENDING, &ser->state);
 266         return tty_wr;
 267 }
 268
 269 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
 270 {
 271         struct ser_device *ser;
 272
 273         if (WARN_ON(!dev))
 274                 return -EINVAL;
 275
 276         ser = netdev_priv(dev);
 277
 278         /* Send flow off once, on high water mark */
 279         if (ser->head.qlen > SEND_QUEUE_HIGH &&
 280                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 281                 ser->common.flowctrl != NULL)
 282
 283                 ser->common.flowctrl(ser->dev, OFF);
 284
 285         skb_queue_tail(&ser->head, skb);
 286         return handle_tx(ser);
 287 }
 288
 289
 290 static void ldisc_tx_wakeup(struct tty_struct *tty)
 291 {
 292         struct ser_device *ser;
 293
 294         ser = tty->disc_data;
 295         BUG_ON(ser == NULL);
 296         WARN_ON(ser->tty != tty);
 297         handle_tx(ser);
 298 }
 299
 300
 301 static void ser_release(struct work_struct *work)
 302 {
 303         struct list_head list;
 304         struct ser_device *ser, *tmp;
 305
 306         spin_lock(&ser_lock);
 307         list_replace_init(&ser_release_list, &list);
 308         spin_unlock(&ser_lock);
 309
 310         if (!list_empty(&list)) {
 311                 rtnl_lock();
 312                 list_for_each_entry_safe(ser, tmp, &list, node) {
 313                         dev_close(ser->dev);
 314                         unregister_netdevice(ser->dev);
 315                         debugfs_deinit(ser);
 316                 }
 317                 rtnl_unlock();
 318         }
 319 }
 320
 321 static DECLARE_WORK(ser_release_work, ser_release);
 322
 323 static int ldisc_open(struct tty_struct *tty)
 324 {
 325         struct ser_device *ser;
 326         struct net_device *dev;
 327         char name[64];
 328         int result;
 329
 330         /* No write no play */
 331         if (tty->ops->write == NULL)
 332                 return -EOPNOTSUPP;
 333         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
 334                 return -EPERM;
 335
 336         /* release devices to avoid name collision */
 337         ser_release(NULL);
 338
 339         result = snprintf(name, sizeof(name), "cf%s", tty->name);
 340         if (result >= IFNAMSIZ)
 341                 return -EINVAL;
 342         dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
 343                            caifdev_setup);
 344         if (!dev)
 345                 return -ENOMEM;
 346
 347         ser = netdev_priv(dev);
 348         ser->tty = tty_kref_get(tty);
 349         ser->dev = dev;
 350         debugfs_init(ser, tty);
 351         tty->receive_room = N_TTY_BUF_SIZE;
 352         tty->disc_data = ser;
 353         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 354         rtnl_lock();
 355         result = register_netdevice(dev);
 356         if (result) {
 357                 rtnl_unlock();
 358                 free_netdev(dev);
 359                 return -ENODEV;
 360         }
 361
 362         spin_lock(&ser_lock);
 363         list_add(&ser->node, &ser_list);
 364         spin_unlock(&ser_lock);
 365         rtnl_unlock();
 366         netif_stop_queue(dev);
 367         update_tty_status(ser);
 368         return 0;
 369 }
 370
 371 static void ldisc_close(struct tty_struct *tty)
 372 {
 373         struct ser_device *ser = tty->disc_data;
 374
 375         tty_kref_put(ser->tty);
 376
 377         spin_lock(&ser_lock);
 378         list_move(&ser->node, &ser_release_list);
 379         spin_unlock(&ser_lock);
 380         schedule_work(&ser_release_work);
 381 }
 382
 383 /* The line discipline structure. */
 384 static struct tty_ldisc_ops caif_ldisc = {
 385         .owner =        THIS_MODULE,
 386         .magic =        TTY_LDISC_MAGIC,
 387         .name =         "n_caif",
 388         .open =         ldisc_open,
 389         .close =        ldisc_close,
 390         .receive_buf =  ldisc_receive,
 391         .write_wakeup = ldisc_tx_wakeup
 392 };
 393
 394 static int register_ldisc(void)
 395 {
 396         int result;
 397
 398         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
 399         if (result < 0) {
 400                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
 401                         result);
 402                 return result;
 403         }
 404         return result;
 405 }
 406 static const struct net_device_ops netdev_ops = {
 407         .ndo_open = caif_net_open,
 408         .ndo_stop = caif_net_close,
 409         .ndo_start_xmit = caif_xmit
 410 };
 411
 412 static void caifdev_setup(struct net_device *dev)
 413 {
 414         struct ser_device *serdev = netdev_priv(dev);
 415
 416         dev->features = 0;
 417         dev->netdev_ops = &netdev_ops;
 418         dev->type = ARPHRD_CAIF;
 419         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
 420         dev->mtu = CAIF_MAX_MTU;
 421         dev->priv_flags |= IFF_NO_QUEUE;
 422         dev->needs_free_netdev = true;
 423         skb_queue_head_init(&serdev->head);
 424         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
 425         serdev->common.use_frag = true;
 426         serdev->common.use_stx = ser_use_stx;
 427         serdev->common.use_fcs = ser_use_fcs;
 428         serdev->dev = dev;
 429 }
 430
 431
 432 static int caif_net_open(struct net_device *dev)
 433 {
 434         netif_wake_queue(dev);
 435         return 0;
 436 }
 437
 438 static int caif_net_close(struct net_device *dev)
 439 {
 440         netif_stop_queue(dev);
 441         return 0;
 442 }
 443
 444 static int __init caif_ser_init(void)
 445 {
 446         int ret;
 447
 448         ret = register_ldisc();
 449         debugfsdir = debugfs_create_dir("caif_serial", NULL);
 450         return ret;
 451 }
 452
 453 static void __exit caif_ser_exit(void)
 454 {
 455         spin_lock(&ser_lock);
 456         list_splice(&ser_list, &ser_release_list);
 457         spin_unlock(&ser_lock);
 458         ser_release(NULL);
 459         cancel_work_sync(&ser_release_work);
 460         tty_unregister_ldisc(N_CAIF);
 461         debugfs_remove_recursive(debugfsdir);
 462 }
 463
 464 module_init(caif_ser_init);
 465 module_exit(caif_ser_exit);