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/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<sjur.brandeland@stericsson.com>");
  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 /*This list is protected by the rtnl lock. */
  39 static LIST_HEAD(ser_list);
  40
  41 static int ser_loop;
  42 module_param(ser_loop, bool, S_IRUGO);
  43 MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
  44
  45 static int ser_use_stx = 1;
  46 module_param(ser_use_stx, bool, S_IRUGO);
  47 MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
  48
  49 static int ser_use_fcs = 1;
  50
  51 module_param(ser_use_fcs, bool, S_IRUGO);
  52 MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
  53
  54 static int ser_write_chunk = MAX_WRITE_CHUNK;
  55 module_param(ser_write_chunk, int, S_IRUGO);
  56
  57 MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
  58
  59 static struct dentry *debugfsdir;
  60
  61 static int caif_net_open(struct net_device *dev);
  62 static int caif_net_close(struct net_device *dev);
  63
  64 struct ser_device {
  65         struct caif_dev_common common;
  66         struct list_head node;
  67         struct net_device *dev;
  68         struct sk_buff_head head;
  69         struct tty_struct *tty;
  70         bool tx_started;
  71         unsigned long state;
  72         char *tty_name;
  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->hw_stopped << 4 |
  92                 ser->tty->flow_stopped << 3 |
  93                 ser->tty->packet << 2 |
  94                 ser->tty->low_latency << 1 |
  95                 ser->tty->warned;
  96 }
  97 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
  98 {
  99         ser->debugfs_tty_dir =
 100                         debugfs_create_dir(tty->name, debugfsdir);
 101         if (!IS_ERR(ser->debugfs_tty_dir)) {
 102                 debugfs_create_blob("last_tx_msg", S_IRUSR,
 103                                 ser->debugfs_tty_dir,
 104                                 &ser->tx_blob);
 105
 106                 debugfs_create_blob("last_rx_msg", S_IRUSR,
 107                                 ser->debugfs_tty_dir,
 108                                 &ser->rx_blob);
 109
 110                 debugfs_create_x32("ser_state", S_IRUSR,
 111                                 ser->debugfs_tty_dir,
 112                                 (u32 *)&ser->state);
 113
 114                 debugfs_create_x8("tty_status", S_IRUSR,
 115                                 ser->debugfs_tty_dir,
 116                                 &ser->tty_status);
 117
 118         }
 119         ser->tx_blob.data = ser->tx_data;
 120         ser->tx_blob.size = 0;
 121         ser->rx_blob.data = ser->rx_data;
 122         ser->rx_blob.size = 0;
 123 }
 124
 125 static inline void debugfs_deinit(struct ser_device *ser)
 126 {
 127         debugfs_remove_recursive(ser->debugfs_tty_dir);
 128 }
 129
 130 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 131 {
 132         if (size > sizeof(ser->rx_data))
 133                 size = sizeof(ser->rx_data);
 134         memcpy(ser->rx_data, data, size);
 135         ser->rx_blob.data = ser->rx_data;
 136         ser->rx_blob.size = size;
 137 }
 138
 139 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 140 {
 141         if (size > sizeof(ser->tx_data))
 142                 size = sizeof(ser->tx_data);
 143         memcpy(ser->tx_data, data, size);
 144         ser->tx_blob.data = ser->tx_data;
 145         ser->tx_blob.size = size;
 146 }
 147 #else
 148 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
 149 {
 150 }
 151
 152 static inline void debugfs_deinit(struct ser_device *ser)
 153 {
 154 }
 155
 156 static inline void update_tty_status(struct ser_device *ser)
 157 {
 158 }
 159
 160 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
 161 {
 162 }
 163
 164 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
 165 {
 166 }
 167
 168 #endif
 169
 170 static void ldisc_receive(struct tty_struct *tty, const u8 *data,
 171                         char *flags, int count)
 172 {
 173         struct sk_buff *skb = NULL;
 174         struct ser_device *ser;
 175         int ret;
 176         u8 *p;
 177
 178         ser = tty->disc_data;
 179
 180         /*
 181          * NOTE: flags may contain information about break or overrun.
 182          * This is not yet handled.
 183          */
 184
 185
 186         /*
 187          * Workaround for garbage at start of transmission,
 188          * only enable if STX handling is not enabled.
 189          */
 190         if (!ser->common.use_stx && !ser->tx_started) {
 191                 dev_info(&ser->dev->dev,
 192                         "Bytes received before initial transmission -"
 193                         "bytes discarded.\n");
 194                 return;
 195         }
 196
 197         BUG_ON(ser->dev == NULL);
 198
 199         /* Get a suitable caif packet and copy in data. */
 200         skb = netdev_alloc_skb(ser->dev, count+1);
 201         if (skb == NULL)
 202                 return;
 203         p = skb_put(skb, count);
 204         memcpy(p, data, count);
 205
 206         skb->protocol = htons(ETH_P_CAIF);
 207         skb_reset_mac_header(skb);
 208         skb->dev = ser->dev;
 209         debugfs_rx(ser, data, count);
 210         /* Push received packet up the stack. */
 211         ret = netif_rx_ni(skb);
 212         if (!ret) {
 213                 ser->dev->stats.rx_packets++;
 214                 ser->dev->stats.rx_bytes += count;
 215         } else
 216                 ++ser->dev->stats.rx_dropped;
 217         update_tty_status(ser);
 218 }
 219
 220 static int handle_tx(struct ser_device *ser)
 221 {
 222         struct tty_struct *tty;
 223         struct sk_buff *skb;
 224         int tty_wr, len, room;
 225
 226         tty = ser->tty;
 227         ser->tx_started = true;
 228
 229         /* Enter critical section */
 230         if (test_and_set_bit(CAIF_SENDING, &ser->state))
 231                 return 0;
 232
 233         /* skb_peek is safe because handle_tx is called after skb_queue_tail */
 234         while ((skb = skb_peek(&ser->head)) != NULL) {
 235
 236                 /* Make sure you don't write too much */
 237                 len = skb->len;
 238                 room = tty_write_room(tty);
 239                 if (!room)
 240                         break;
 241                 if (room > ser_write_chunk)
 242                         room = ser_write_chunk;
 243                 if (len > room)
 244                         len = room;
 245
 246                 /* Write to tty or loopback */
 247                 if (!ser_loop) {
 248                         tty_wr = tty->ops->write(tty, skb->data, len);
 249                         update_tty_status(ser);
 250                 } else {
 251                         tty_wr = len;
 252                         ldisc_receive(tty, skb->data, NULL, len);
 253                 }
 254                 ser->dev->stats.tx_packets++;
 255                 ser->dev->stats.tx_bytes += tty_wr;
 256
 257                 /* Error on TTY ?! */
 258                 if (tty_wr < 0)
 259                         goto error;
 260                 /* Reduce buffer written, and discard if empty */
 261                 skb_pull(skb, tty_wr);
 262                 if (skb->len == 0) {
 263                         struct sk_buff *tmp = skb_dequeue(&ser->head);
 264                         BUG_ON(tmp != skb);
 265                         if (in_interrupt())
 266                                 dev_kfree_skb_irq(skb);
 267                         else
 268                                 kfree_skb(skb);
 269                 }
 270         }
 271         /* Send flow off if queue is empty */
 272         if (ser->head.qlen <= SEND_QUEUE_LOW &&
 273                 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 274                 ser->common.flowctrl != NULL)
 275                                 ser->common.flowctrl(ser->dev, ON);
 276         clear_bit(CAIF_SENDING, &ser->state);
 277         return 0;
 278 error:
 279         clear_bit(CAIF_SENDING, &ser->state);
 280         return tty_wr;
 281 }
 282
 283 static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
 284 {
 285         struct ser_device *ser;
 286
 287         BUG_ON(dev == NULL);
 288         ser = netdev_priv(dev);
 289
 290         /* Send flow off once, on high water mark */
 291         if (ser->head.qlen > SEND_QUEUE_HIGH &&
 292                 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
 293                 ser->common.flowctrl != NULL)
 294
 295                 ser->common.flowctrl(ser->dev, OFF);
 296
 297         skb_queue_tail(&ser->head, skb);
 298         return handle_tx(ser);
 299 }
 300
 301
 302 static void ldisc_tx_wakeup(struct tty_struct *tty)
 303 {
 304         struct ser_device *ser;
 305
 306         ser = tty->disc_data;
 307         BUG_ON(ser == NULL);
 308         BUG_ON(ser->tty != tty);
 309         handle_tx(ser);
 310 }
 311
 312
 313 static int ldisc_open(struct tty_struct *tty)
 314 {
 315         struct ser_device *ser;
 316         struct net_device *dev;
 317         char name[64];
 318         int result;
 319
 320         /* No write no play */
 321         if (tty->ops->write == NULL)
 322                 return -EOPNOTSUPP;
 323         if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
 324                 return -EPERM;
 325
 326         sprintf(name, "cf%s", tty->name);
 327         dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
 328         ser = netdev_priv(dev);
 329         ser->tty = tty_kref_get(tty);
 330         ser->dev = dev;
 331         debugfs_init(ser, tty);
 332         tty->receive_room = N_TTY_BUF_SIZE;
 333         tty->disc_data = ser;
 334         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 335         rtnl_lock();
 336         result = register_netdevice(dev);
 337         if (result) {
 338                 rtnl_unlock();
 339                 free_netdev(dev);
 340                 return -ENODEV;
 341         }
 342
 343         list_add(&ser->node, &ser_list);
 344         rtnl_unlock();
 345         netif_stop_queue(dev);
 346         update_tty_status(ser);
 347         return 0;
 348 }
 349
 350 static void ldisc_close(struct tty_struct *tty)
 351 {
 352         struct ser_device *ser = tty->disc_data;
 353         /* Remove may be called inside or outside of rtnl_lock */
 354         int islocked = rtnl_is_locked();
 355
 356         if (!islocked)
 357                 rtnl_lock();
 358         /* device is freed automagically by net-sysfs */
 359         dev_close(ser->dev);
 360         unregister_netdevice(ser->dev);
 361         list_del(&ser->node);
 362         debugfs_deinit(ser);
 363         tty_kref_put(ser->tty);
 364         if (!islocked)
 365                 rtnl_unlock();
 366 }
 367
 368 /* The line discipline structure. */
 369 static struct tty_ldisc_ops caif_ldisc = {
 370         .owner =        THIS_MODULE,
 371         .magic =        TTY_LDISC_MAGIC,
 372         .name =         "n_caif",
 373         .open =         ldisc_open,
 374         .close =        ldisc_close,
 375         .receive_buf =  ldisc_receive,
 376         .write_wakeup = ldisc_tx_wakeup
 377 };
 378
 379 static int register_ldisc(void)
 380 {
 381         int result;
 382
 383         result = tty_register_ldisc(N_CAIF, &caif_ldisc);
 384         if (result < 0) {
 385                 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
 386                         result);
 387                 return result;
 388         }
 389         return result;
 390 }
 391 static const struct net_device_ops netdev_ops = {
 392         .ndo_open = caif_net_open,
 393         .ndo_stop = caif_net_close,
 394         .ndo_start_xmit = caif_xmit
 395 };
 396
 397 static void caifdev_setup(struct net_device *dev)
 398 {
 399         struct ser_device *serdev = netdev_priv(dev);
 400
 401         dev->features = 0;
 402         dev->netdev_ops = &netdev_ops;
 403         dev->type = ARPHRD_CAIF;
 404         dev->flags = IFF_POINTOPOINT | IFF_NOARP;
 405         dev->mtu = CAIF_MAX_MTU;
 406         dev->tx_queue_len = 0;
 407         dev->destructor = free_netdev;
 408         skb_queue_head_init(&serdev->head);
 409         serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
 410         serdev->common.use_frag = true;
 411         serdev->common.use_stx = ser_use_stx;
 412         serdev->common.use_fcs = ser_use_fcs;
 413         serdev->dev = dev;
 414 }
 415
 416
 417 static int caif_net_open(struct net_device *dev)
 418 {
 419         netif_wake_queue(dev);
 420         return 0;
 421 }
 422
 423 static int caif_net_close(struct net_device *dev)
 424 {
 425         netif_stop_queue(dev);
 426         return 0;
 427 }
 428
 429 static int __init caif_ser_init(void)
 430 {
 431         int ret;
 432
 433         ret = register_ldisc();
 434         debugfsdir = debugfs_create_dir("caif_serial", NULL);
 435         return ret;
 436 }
 437
 438 static void __exit caif_ser_exit(void)
 439 {
 440         struct ser_device *ser = NULL;
 441         struct list_head *node;
 442         struct list_head *_tmp;
 443
 444         list_for_each_safe(node, _tmp, &ser_list) {
 445                 ser = list_entry(node, struct ser_device, node);
 446                 dev_close(ser->dev);
 447                 unregister_netdevice(ser->dev);
 448                 list_del(node);
 449         }
 450         tty_unregister_ldisc(N_CAIF);
 451         debugfs_remove_recursive(debugfsdir);
 452 }
 453
 454 module_init(caif_ser_init);
 455 module_exit(caif_ser_exit);