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 =
  98                         debugfs_create_dir(tty->name, debugfsdir);
  99         if (!IS_ERR(ser->debugfs_tty_dir)) {
 100                 debugfs_create_blob("last_tx_msg", 0400,
 101                                     ser->debugfs_tty_dir,
 102                                     &ser->tx_blob);
 103
 104                 debugfs_create_blob("last_rx_msg", 0400,
 105                                     ser->debugfs_tty_dir,
 106                                     &ser->rx_blob);
 107
 108                 debugfs_create_x32("ser_state", 0400,
 109                                    ser->debugfs_tty_dir,
 110                                    (u32 *)&ser->state);
 111
 112                 debugfs_create_x8("tty_status", 0400,
 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
 175         ser = tty->disc_data;
 176
 177         /*
 178          * NOTE: flags may contain information about break or overrun.
 179          * This is not yet handled.
 180          */
 181
 182
 183         /*
 184          * Workaround for garbage at start of transmission,
 185          * only enable if STX handling is not enabled.
 186          */
 187         if (!ser->common.use_stx && !ser->tx_started) {
 188                 dev_info(&ser->dev->dev,
 189                         "Bytes received before initial transmission -"
 190                         "bytes discarded.\n");
 191                 return;
 192         }
 193
 194         BUG_ON(ser->dev == NULL);
 195
 196         /* Get a suitable caif packet and copy in data. */
 197         skb = netdev_alloc_skb(ser->dev, count+1);
 198         if (skb == NULL)
 199                 return;
 200         skb_put_data(skb, data, count);
 201
 202         skb->protocol = htons(ETH_P_CAIF);
 203         skb_reset_mac_header(skb);
 204         debugfs_rx(ser, data, count);
 205         /* Push received packet up the stack. */
 206         ret = netif_rx_ni(skb);
 207         if (!ret) {
 208                 ser->dev->stats.rx_packets++;
 209                 ser->dev->stats.rx_bytes += count;
 210         } else
 211                 ++ser->dev->stats.rx_dropped;
 212         update_tty_status(ser);
 213 }
 214
 215 static int handle_tx(struct ser_device *ser)
 216 {
 217         struct tty_struct *tty;
 218         struct sk_buff *skb;
 219         int tty_wr, len, room;
 220
 221         tty = ser->tty;
 222         ser->tx_started = true;
 223
 224         /* Enter critical section */
 225         if (test_and_set_bit(CAIF_SENDING, &ser->state))
 226                 return 0;
 227
 228         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
 229         while ((skb = skb_peek(&ser->head)) != NULL) {
 230
 231                 /* Make sure you don't write too much */
 232                 len = skb->len;
 233                 room = tty_write_room(tty);
 234                 if (!room)
 235                         break;
 236                 if (room > ser_write_chunk)
 237                         room = ser_write_chunk;
 238                 if (len > room)
 239                         len = room;
 240
 241                 /* Write to tty or loopback */
 242                 if (!ser_loop) {
 243                         tty_wr = tty->ops->write(tty, skb->data, len);
 244                         update_tty_status(ser);
 245                 } else {
 246                         tty_wr = len;
 247                         ldisc_receive(tty, skb->data, NULL, len);
 248                 }
 249                 ser->dev->stats.tx_packets++;
 250                 ser->dev->stats.tx_bytes += tty_wr;
 251
 252                 /* Error on TTY ?! */
 253                 if (tty_wr < 0)
 254                         goto error;
 255                 /* Reduce buffer written, and discard if empty */
 256                 skb_pull(skb, tty_wr);
 257                 if (skb->len == 0) {
 258                         struct sk_buff *tmp = skb_dequeue(&ser->head);
 259                         WARN_ON(tmp != skb);
 260                         dev_consume_skb_any(skb);
 261                 }
 262         }
 263         /* Send flow off if queue is empty */
 264         if (ser->head.qlen <= SEND_QUEUE_LOW &&
 265                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 266                 ser->common.flowctrl != NULL)
 267                                 ser->common.flowctrl(ser->dev, ON);
 268         clear_bit(CAIF_SENDING, &ser->state);
 269         return 0;
 270 error:
 271         clear_bit(CAIF_SENDING, &ser->state);
 272         return tty_wr;
 273 }
 274
 275 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
 276 {
 277         struct ser_device *ser;
 278
 279         BUG_ON(dev == NULL);
 280         ser = netdev_priv(dev);
 281
 282         /* Send flow off once, on high water mark */
 283         if (ser->head.qlen > SEND_QUEUE_HIGH &&
 284                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 285                 ser->common.flowctrl != NULL)
 286
 287                 ser->common.flowctrl(ser->dev, OFF);
 288
 289         skb_queue_tail(&ser->head, skb);
 290         return handle_tx(ser);
 291 }
 292
 293
 294 static void ldisc_tx_wakeup(struct tty_struct *tty)
 295 {
 296         struct ser_device *ser;
 297
 298         ser = tty->disc_data;
 299         BUG_ON(ser == NULL);
 300         WARN_ON(ser->tty != tty);
 301         handle_tx(ser);
 302 }
 303
 304
 305 static void ser_release(struct work_struct *work)
 306 {
 307         struct list_head list;
 308         struct ser_device *ser, *tmp;
 309
 310         spin_lock(&ser_lock);
 311         list_replace_init(&ser_release_list, &list);
 312         spin_unlock(&ser_lock);
 313
 314         if (!list_empty(&list)) {
 315                 rtnl_lock();
 316                 list_for_each_entry_safe(ser, tmp, &list, node) {
 317                         dev_close(ser->dev);
 318                         unregister_netdevice(ser->dev);
 319                         debugfs_deinit(ser);
 320                 }
 321                 rtnl_unlock();
 322         }
 323 }
 324
 325 static DECLARE_WORK(ser_release_work, ser_release);
 326
 327 static int ldisc_open(struct tty_struct *tty)
 328 {
 329         struct ser_device *ser;
 330         struct net_device *dev;
 331         char name[64];
 332         int result;
 333
 334         /* No write no play */
 335         if (tty->ops->write == NULL)
 336                 return -EOPNOTSUPP;
 337         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
 338                 return -EPERM;
 339
 340         /* release devices to avoid name collision */
 341         ser_release(NULL);
 342
 343         result = snprintf(name, sizeof(name), "cf%s", tty->name);
 344         if (result >= IFNAMSIZ)
 345                 return -EINVAL;
 346         dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
 347                            caifdev_setup);
 348         if (!dev)
 349                 return -ENOMEM;
 350
 351         ser = netdev_priv(dev);
 352         ser->tty = tty_kref_get(tty);
 353         ser->dev = dev;
 354         debugfs_init(ser, tty);
 355         tty->receive_room = N_TTY_BUF_SIZE;
 356         tty->disc_data = ser;
 357         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 358         rtnl_lock();
 359         result = register_netdevice(dev);
 360         if (result) {
 361                 rtnl_unlock();
 362                 free_netdev(dev);
 363                 return -ENODEV;
 364         }
 365
 366         spin_lock(&ser_lock);
 367         list_add(&ser->node, &ser_list);
 368         spin_unlock(&ser_lock);
 369         rtnl_unlock();
 370         netif_stop_queue(dev);
 371         update_tty_status(ser);
 372         return 0;
 373 }
 374
 375 static void ldisc_close(struct tty_struct *tty)
 376 {
 377         struct ser_device *ser = tty->disc_data;
 378
 379         tty_kref_put(ser->tty);
 380
 381         spin_lock(&ser_lock);
 382         list_move(&ser->node, &ser_release_list);
 383         spin_unlock(&ser_lock);
 384         schedule_work(&ser_release_work);
 385 }
 386
 387 /* The line discipline structure. */
 388 static struct tty_ldisc_ops caif_ldisc = {
 389         .owner =        THIS_MODULE,
 390         .magic =        TTY_LDISC_MAGIC,
 391         .name =         "n_caif",
 392         .open =         ldisc_open,
 393         .close =        ldisc_close,
 394         .receive_buf =  ldisc_receive,
 395         .write_wakeup = ldisc_tx_wakeup
 396 };
 397
 398 static int register_ldisc(void)
 399 {
 400         int result;
 401
 402         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
 403         if (result < 0) {
 404                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
 405                         result);
 406                 return result;
 407         }
 408         return result;
 409 }
 410 static const struct net_device_ops netdev_ops = {
 411         .ndo_open = caif_net_open,
 412         .ndo_stop = caif_net_close,
 413         .ndo_start_xmit = caif_xmit
 414 };
 415
 416 static void caifdev_setup(struct net_device *dev)
 417 {
 418         struct ser_device *serdev = netdev_priv(dev);
 419
 420         dev->features = 0;
 421         dev->netdev_ops = &netdev_ops;
 422         dev->type = ARPHRD_CAIF;
 423         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
 424         dev->mtu = CAIF_MAX_MTU;
 425         dev->priv_flags |= IFF_NO_QUEUE;
 426         dev->needs_free_netdev = true;
 427         skb_queue_head_init(&serdev->head);
 428         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
 429         serdev->common.use_frag = true;
 430         serdev->common.use_stx = ser_use_stx;
 431         serdev->common.use_fcs = ser_use_fcs;
 432         serdev->dev = dev;
 433 }
 434
 435
 436 static int caif_net_open(struct net_device *dev)
 437 {
 438         netif_wake_queue(dev);
 439         return 0;
 440 }
 441
 442 static int caif_net_close(struct net_device *dev)
 443 {
 444         netif_stop_queue(dev);
 445         return 0;
 446 }
 447
 448 static int __init caif_ser_init(void)
 449 {
 450         int ret;
 451
 452         ret = register_ldisc();
 453         debugfsdir = debugfs_create_dir("caif_serial", NULL);
 454         return ret;
 455 }
 456
 457 static void __exit caif_ser_exit(void)
 458 {
 459         spin_lock(&ser_lock);
 460         list_splice(&ser_list, &ser_release_list);
 461         spin_unlock(&ser_lock);
 462         ser_release(NULL);
 463         cancel_work_sync(&ser_release_work);
 464         tty_unregister_ldisc(N_CAIF);
 465         debugfs_remove_recursive(debugfsdir);
 466 }
 467
 468 module_init(caif_ser_init);
 469 module_exit(caif_ser_exit);