drivers/net/caif/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/version.h>
  10 #include <linux/module.h>
  11 #include <linux/device.h>
  12 #include <linux/types.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/netdevice.h>
  15 #include <linux/rtnetlink.h>
  16 #include <linux/tty.h>
  17 #include <linux/file.h>
  18 #include <linux/if_arp.h>
  19 #include <net/caif/caif_device.h>
  20 #include <net/caif/cfcnfg.h>
  21 #include <linux/err.h>
  22 #include <linux/debugfs.h>
  23
  24 MODULE_LICENSE("GPL");
  25 MODULE_AUTHOR("Sjur Brendeland<sjur.brandeland@stericsson.com>");
  26 MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
  27 MODULE_LICENSE("GPL");
  28 MODULE_ALIAS_LDISC(N_CAIF);
  29
  30 #define SEND_QUEUE_LOW 10
  31 #define SEND_QUEUE_HIGH 100
  32 #define CAIF_SENDING            1 /* Bit 1 = 0x02*/
  33 #define CAIF_FLOW_OFF_SENT      4 /* Bit 4 = 0x10 */
  34 #define MAX_WRITE_CHUNK      4096
  35 #define ON 1
  36 #define OFF 0
  37 #define CAIF_MAX_MTU 4096
  38
  39 /*This list is protected by the rtnl lock. */
  40 static LIST_HEAD(ser_list);
  41
  42 static int ser_loop;
  43 module_param(ser_loop, bool, S_IRUGO);
  44 MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
  45
  46 static int ser_use_stx = 1;
  47 module_param(ser_use_stx, bool, S_IRUGO);
  48 MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
  49
  50 static int ser_use_fcs = 1;
  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->hw_stopped << 4 |
  93                 ser->tty->flow_stopped << 3 |
  94                 ser->tty->packet << 2 |
  95                 ser->tty->low_latency << 1 |
  96                 ser->tty->warned;
  97 }
  98 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
  99 {
 100         ser->debugfs_tty_dir =
 101                         debugfs_create_dir(tty->name, debugfsdir);
 102         if (!IS_ERR(ser->debugfs_tty_dir)) {
 103                 debugfs_create_blob("last_tx_msg", S_IRUSR,
 104                                 ser->debugfs_tty_dir,
 105                                 &ser->tx_blob);
 106
 107                 debugfs_create_blob("last_rx_msg", S_IRUSR,
 108                                 ser->debugfs_tty_dir,
 109                                 &ser->rx_blob);
 110
 111                 debugfs_create_x32("ser_state", S_IRUSR,
 112                                 ser->debugfs_tty_dir,
 113                                 (u32 *)&ser->state);
 114
 115                 debugfs_create_x8("tty_status", S_IRUSR,
 116                                 ser->debugfs_tty_dir,
 117                                 &ser->tty_status);
 118
 119         }
 120         ser->tx_blob.data = ser->tx_data;
 121         ser->tx_blob.size = 0;
 122         ser->rx_blob.data = ser->rx_data;
 123         ser->rx_blob.size = 0;
 124 }
 125
 126 static inline void debugfs_deinit(struct ser_device *ser)
 127 {
 128         debugfs_remove_recursive(ser->debugfs_tty_dir);
 129 }
 130
 131 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 132 {
 133         if (size > sizeof(ser->rx_data))
 134                 size = sizeof(ser->rx_data);
 135         memcpy(ser->rx_data, data, size);
 136         ser->rx_blob.data = ser->rx_data;
 137         ser->rx_blob.size = size;
 138 }
 139
 140 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 141 {
 142         if (size > sizeof(ser->tx_data))
 143                 size = sizeof(ser->tx_data);
 144         memcpy(ser->tx_data, data, size);
 145         ser->tx_blob.data = ser->tx_data;
 146         ser->tx_blob.size = size;
 147 }
 148 #else
 149 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
 150 {
 151 }
 152
 153 static inline void debugfs_deinit(struct ser_device *ser)
 154 {
 155 }
 156
 157 static inline void update_tty_status(struct ser_device *ser)
 158 {
 159 }
 160
 161 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 162 {
 163 }
 164
 165 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 166 {
 167 }
 168
 169 #endif
 170
 171 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
 172                         char *flags, int count)
 173 {
 174         struct sk_buff *skb = NULL;
 175         struct ser_device *ser;
 176         int ret;
 177         u8 *p;
 178
 179         ser = tty->disc_data;
 180
 181         /*
 182          * NOTE: flags may contain information about break or overrun.
 183          * This is not yet handled.
 184          */
 185
 186
 187         /*
 188          * Workaround for garbage at start of transmission,
 189          * only enable if STX handling is not enabled.
 190          */
 191         if (!ser->common.use_stx && !ser->tx_started) {
 192                 dev_info(&ser->dev->dev,
 193                         "Bytes received before initial transmission -"
 194                         "bytes discarded.\n");
 195                 return;
 196         }
 197
 198         BUG_ON(ser->dev == NULL);
 199
 200         /* Get a suitable caif packet and copy in data. */
 201         skb = netdev_alloc_skb(ser->dev, count+1);
 202         if (skb == NULL)
 203                 return;
 204         p = skb_put(skb, count);
 205         memcpy(p, data, count);
 206
 207         skb->protocol = htons(ETH_P_CAIF);
 208         skb_reset_mac_header(skb);
 209         skb->dev = ser->dev;
 210         debugfs_rx(ser, data, count);
 211         /* Push received packet up the stack. */
 212         ret = netif_rx_ni(skb);
 213         if (!ret) {
 214                 ser->dev->stats.rx_packets++;
 215                 ser->dev->stats.rx_bytes += count;
 216         } else
 217                 ++ser->dev->stats.rx_dropped;
 218         update_tty_status(ser);
 219 }
 220
 221 static int handle_tx(struct ser_device *ser)
 222 {
 223         struct tty_struct *tty;
 224         struct sk_buff *skb;
 225         int tty_wr, len, room;
 226
 227         tty = ser->tty;
 228         ser->tx_started = true;
 229
 230         /* Enter critical section */
 231         if (test_and_set_bit(CAIF_SENDING, &ser->state))
 232                 return 0;
 233
 234         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
 235         while ((skb = skb_peek(&ser->head)) != NULL) {
 236
 237                 /* Make sure you don't write too much */
 238                 len = skb->len;
 239                 room = tty_write_room(tty);
 240                 if (!room)
 241                         break;
 242                 if (room > ser_write_chunk)
 243                         room = ser_write_chunk;
 244                 if (len > room)
 245                         len = room;
 246
 247                 /* Write to tty or loopback */
 248                 if (!ser_loop) {
 249                         tty_wr = tty->ops->write(tty, skb->data, len);
 250                         update_tty_status(ser);
 251                 } else {
 252                         tty_wr = len;
 253                         ldisc_receive(tty, skb->data, NULL, len);
 254                 }
 255                 ser->dev->stats.tx_packets++;
 256                 ser->dev->stats.tx_bytes += tty_wr;
 257
 258                 /* Error on TTY ?! */
 259                 if (tty_wr < 0)
 260                         goto error;
 261                 /* Reduce buffer written, and discard if empty */
 262                 skb_pull(skb, tty_wr);
 263                 if (skb->len == 0) {
 264                         struct sk_buff *tmp = skb_dequeue(&ser->head);
 265                         BUG_ON(tmp != skb);
 266                         if (in_interrupt())
 267                                 dev_kfree_skb_irq(skb);
 268                         else
 269                                 kfree_skb(skb);
 270                 }
 271         }
 272         /* Send flow off if queue is empty */
 273         if (ser->head.qlen <= SEND_QUEUE_LOW &&
 274                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 275                 ser->common.flowctrl != NULL)
 276                                 ser->common.flowctrl(ser->dev, ON);
 277         clear_bit(CAIF_SENDING, &ser->state);
 278         return 0;
 279 error:
 280         clear_bit(CAIF_SENDING, &ser->state);
 281         return tty_wr;
 282 }
 283
 284 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
 285 {
 286         struct ser_device *ser;
 287
 288         BUG_ON(dev == NULL);
 289         ser = netdev_priv(dev);
 290
 291         /* Send flow off once, on high water mark */
 292         if (ser->head.qlen > SEND_QUEUE_HIGH &&
 293                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 294                 ser->common.flowctrl != NULL)
 295
 296                 ser->common.flowctrl(ser->dev, OFF);
 297
 298         skb_queue_tail(&ser->head, skb);
 299         return handle_tx(ser);
 300 }
 301
 302
 303 static void ldisc_tx_wakeup(struct tty_struct *tty)
 304 {
 305         struct ser_device *ser;
 306
 307         ser = tty->disc_data;
 308         BUG_ON(ser == NULL);
 309         BUG_ON(ser->tty != tty);
 310         handle_tx(ser);
 311 }
 312
 313
 314 static int ldisc_open(struct tty_struct *tty)
 315 {
 316         struct ser_device *ser;
 317         struct net_device *dev;
 318         char name[64];
 319         int result;
 320
 321         /* No write no play */
 322         if (tty->ops->write == NULL)
 323                 return -EOPNOTSUPP;
 324         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
 325                 return -EPERM;
 326
 327         sprintf(name, "cf%s", tty->name);
 328         dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
 329         ser = netdev_priv(dev);
 330         ser->tty = tty_kref_get(tty);
 331         ser->dev = dev;
 332         debugfs_init(ser, tty);
 333         tty->receive_room = N_TTY_BUF_SIZE;
 334         tty->disc_data = ser;
 335         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 336         rtnl_lock();
 337         result = register_netdevice(dev);
 338         if (result) {
 339                 rtnl_unlock();
 340                 free_netdev(dev);
 341                 return -ENODEV;
 342         }
 343
 344         list_add(&ser->node, &ser_list);
 345         rtnl_unlock();
 346         netif_stop_queue(dev);
 347         update_tty_status(ser);
 348         return 0;
 349 }
 350
 351 static void ldisc_close(struct tty_struct *tty)
 352 {
 353         struct ser_device *ser = tty->disc_data;
 354         /* Remove may be called inside or outside of rtnl_lock */
 355         int islocked = rtnl_is_locked();
 356
 357         if (!islocked)
 358                 rtnl_lock();
 359         /* device is freed automagically by net-sysfs */
 360         dev_close(ser->dev);
 361         unregister_netdevice(ser->dev);
 362         list_del(&ser->node);
 363         debugfs_deinit(ser);
 364         tty_kref_put(ser->tty);
 365         if (!islocked)
 366                 rtnl_unlock();
 367 }
 368
 369 /* The line discipline structure. */
 370 static struct tty_ldisc_ops caif_ldisc = {
 371         .owner =        THIS_MODULE,
 372         .magic =        TTY_LDISC_MAGIC,
 373         .name =         "n_caif",
 374         .open =         ldisc_open,
 375         .close =        ldisc_close,
 376         .receive_buf =  ldisc_receive,
 377         .write_wakeup = ldisc_tx_wakeup
 378 };
 379
 380 static int register_ldisc(void)
 381 {
 382         int result;
 383
 384         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
 385         if (result < 0) {
 386                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
 387                         result);
 388                 return result;
 389         }
 390         return result;
 391 }
 392 static const struct net_device_ops netdev_ops = {
 393         .ndo_open = caif_net_open,
 394         .ndo_stop = caif_net_close,
 395         .ndo_start_xmit = caif_xmit
 396 };
 397
 398 static void caifdev_setup(struct net_device *dev)
 399 {
 400         struct ser_device *serdev = netdev_priv(dev);
 401
 402         dev->features = 0;
 403         dev->netdev_ops = &netdev_ops;
 404         dev->type = ARPHRD_CAIF;
 405         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
 406         dev->mtu = CAIF_MAX_MTU;
 407         dev->tx_queue_len = 0;
 408         dev->destructor = free_netdev;
 409         skb_queue_head_init(&serdev->head);
 410         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
 411         serdev->common.use_frag = true;
 412         serdev->common.use_stx = ser_use_stx;
 413         serdev->common.use_fcs = ser_use_fcs;
 414         serdev->dev = dev;
 415 }
 416
 417
 418 static int caif_net_open(struct net_device *dev)
 419 {
 420         netif_wake_queue(dev);
 421         return 0;
 422 }
 423
 424 static int caif_net_close(struct net_device *dev)
 425 {
 426         netif_stop_queue(dev);
 427         return 0;
 428 }
 429
 430 static int __init caif_ser_init(void)
 431 {
 432         int ret;
 433
 434         ret = register_ldisc();
 435         debugfsdir = debugfs_create_dir("caif_serial", NULL);
 436         return ret;
 437 }
 438
 439 static void __exit caif_ser_exit(void)
 440 {
 441         struct ser_device *ser = NULL;
 442         struct list_head *node;
 443         struct list_head *_tmp;
 444
 445         list_for_each_safe(node, _tmp, &ser_list) {
 446                 ser = list_entry(node, struct ser_device, node);
 447                 dev_close(ser->dev);
 448                 unregister_netdevice(ser->dev);
 449                 list_del(node);
 450         }
 451         tty_unregister_ldisc(N_CAIF);
 452         debugfs_remove_recursive(debugfsdir);
 453 }
 454
 455 module_init(caif_ser_init);
 456 module_exit(caif_ser_exit);