drivers/net/can/slcan.c

   1 /*
   2  * slcan.c - serial line CAN interface driver (using tty line discipline)
   3  *
   4  * This file is derived from linux/drivers/net/slip/slip.c
   5  *
   6  * slip.c Authors  : Laurence Culhane <loz@holmes.demon.co.uk>
   7  *                   Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
   8  * slcan.c Author  : Oliver Hartkopp <socketcan@hartkopp.net>
   9  *
  10  * This program is free software; you can redistribute it and/or modify it
  11  * under the terms of the GNU General Public License as published by the
  12  * Free Software Foundation; either version 2 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License along
  21  * with this program; if not, see http://www.gnu.org/licenses/gpl.html
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  24  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  25  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  26  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  27  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  28  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  29  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  30  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  31  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  32  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  33  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  34  * DAMAGE.
  35  *
  36  */
  37
  38 #include <linux/module.h>
  39 #include <linux/moduleparam.h>
  40
  41 #include <linux/uaccess.h>
  42 #include <linux/bitops.h>
  43 #include <linux/string.h>
  44 #include <linux/tty.h>
  45 #include <linux/errno.h>
  46 #include <linux/netdevice.h>
  47 #include <linux/skbuff.h>
  48 #include <linux/rtnetlink.h>
  49 #include <linux/if_arp.h>
  50 #include <linux/if_ether.h>
  51 #include <linux/sched.h>
  52 #include <linux/delay.h>
  53 #include <linux/init.h>
  54 #include <linux/kernel.h>
  55 #include <linux/workqueue.h>
  56 #include <linux/can.h>
  57 #include <linux/can/skb.h>
  58 #include <linux/can/can-ml.h>
  59
  60 MODULE_ALIAS_LDISC(N_SLCAN);
  61 MODULE_DESCRIPTION("serial line CAN interface");
  62 MODULE_LICENSE("GPL");
  63 MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
  64
  65 #define SLCAN_MAGIC 0x53CA
  66
  67 static int maxdev = 10;         /* MAX number of SLCAN channels;
  68                                    This can be overridden with
  69                                    insmod slcan.ko maxdev=nnn   */
  70 module_param(maxdev, int, 0);
  71 MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
  72
  73 /* maximum rx buffer len: extended CAN frame with timestamp */
  74 #define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
  75
  76 #define SLC_CMD_LEN 1
  77 #define SLC_SFF_ID_LEN 3
  78 #define SLC_EFF_ID_LEN 8
  79
  80 struct slcan {
  81         int                     magic;
  82
  83         /* Various fields. */
  84         struct tty_struct       *tty;           /* ptr to TTY structure      */
  85         struct net_device       *dev;           /* easy for intr handling    */
  86         spinlock_t              lock;
  87         struct work_struct      tx_work;        /* Flushes transmit buffer   */
  88
  89         /* These are pointers to the malloc()ed frame buffers. */
  90         unsigned char           rbuff[SLC_MTU]; /* receiver buffer           */
  91         int                     rcount;         /* received chars counter    */
  92         unsigned char           xbuff[SLC_MTU]; /* transmitter buffer        */
  93         unsigned char           *xhead;         /* pointer to next XMIT byte */
  94         int                     xleft;          /* bytes left in XMIT queue  */
  95
  96         unsigned long           flags;          /* Flag values/ mode etc     */
  97 #define SLF_INUSE               0               /* Channel in use            */
  98 #define SLF_ERROR               1               /* Parity, etc. error        */
  99 };
 100
 101 static struct net_device **slcan_devs;
 102
 103  /************************************************************************
 104   *                     SLCAN ENCAPSULATION FORMAT                       *
 105   ************************************************************************/
 106
 107 /*
 108  * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
 109  * frame format) a data length code (can_dlc) which can be from 0 to 8
 110  * and up to <can_dlc> data bytes as payload.
 111  * Additionally a CAN frame may become a remote transmission frame if the
 112  * RTR-bit is set. This causes another ECU to send a CAN frame with the
 113  * given can_id.
 114  *
 115  * The SLCAN ASCII representation of these different frame types is:
 116  * <type> <id> <dlc> <data>*
 117  *
 118  * Extended frames (29 bit) are defined by capital characters in the type.
 119  * RTR frames are defined as 'r' types - normal frames have 't' type:
 120  * t => 11 bit data frame
 121  * r => 11 bit RTR frame
 122  * T => 29 bit data frame
 123  * R => 29 bit RTR frame
 124  *
 125  * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
 126  * The <dlc> is a one byte ASCII number ('0' - '8')
 127  * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
 128  *
 129  * Examples:
 130  *
 131  * t1230 : can_id 0x123, can_dlc 0, no data
 132  * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
 133  * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
 134  * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
 135  *
 136  */
 137
 138  /************************************************************************
 139   *                     STANDARD SLCAN DECAPSULATION                     *
 140   ************************************************************************/
 141
 142 /* Send one completely decapsulated can_frame to the network layer */
 143 static void slc_bump(struct slcan *sl)
 144 {
 145         struct sk_buff *skb;
 146         struct can_frame cf;
 147         int i, tmp;
 148         u32 tmpid;
 149         char *cmd = sl->rbuff;
 150
 151         cf.can_id = 0;
 152
 153         switch (*cmd) {
 154         case 'r':
 155                 cf.can_id = CAN_RTR_FLAG;
 156                 /* fallthrough */
 157         case 't':
 158                 /* store dlc ASCII value and terminate SFF CAN ID string */
 159                 cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
 160                 sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN] = 0;
 161                 /* point to payload data behind the dlc */
 162                 cmd += SLC_CMD_LEN + SLC_SFF_ID_LEN + 1;
 163                 break;
 164         case 'R':
 165                 cf.can_id = CAN_RTR_FLAG;
 166                 /* fallthrough */
 167         case 'T':
 168                 cf.can_id |= CAN_EFF_FLAG;
 169                 /* store dlc ASCII value and terminate EFF CAN ID string */
 170                 cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
 171                 sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN] = 0;
 172                 /* point to payload data behind the dlc */
 173                 cmd += SLC_CMD_LEN + SLC_EFF_ID_LEN + 1;
 174                 break;
 175         default:
 176                 return;
 177         }
 178
 179         if (kstrtou32(sl->rbuff + SLC_CMD_LEN, 16, &tmpid))
 180                 return;
 181
 182         cf.can_id |= tmpid;
 183
 184         /* get can_dlc from sanitized ASCII value */
 185         if (cf.can_dlc >= '0' && cf.can_dlc < '9')
 186                 cf.can_dlc -= '0';
 187         else
 188                 return;
 189
 190         *(u64 *) (&cf.data) = 0; /* clear payload */
 191
 192         /* RTR frames may have a dlc > 0 but they never have any data bytes */
 193         if (!(cf.can_id & CAN_RTR_FLAG)) {
 194                 for (i = 0; i < cf.can_dlc; i++) {
 195                         tmp = hex_to_bin(*cmd++);
 196                         if (tmp < 0)
 197                                 return;
 198                         cf.data[i] = (tmp << 4);
 199                         tmp = hex_to_bin(*cmd++);
 200                         if (tmp < 0)
 201                                 return;
 202                         cf.data[i] |= tmp;
 203                 }
 204         }
 205
 206         skb = dev_alloc_skb(sizeof(struct can_frame) +
 207                             sizeof(struct can_skb_priv));
 208         if (!skb)
 209                 return;
 210
 211         skb->dev = sl->dev;
 212         skb->protocol = htons(ETH_P_CAN);
 213         skb->pkt_type = PACKET_BROADCAST;
 214         skb->ip_summed = CHECKSUM_UNNECESSARY;
 215
 216         can_skb_reserve(skb);
 217         can_skb_prv(skb)->ifindex = sl->dev->ifindex;
 218         can_skb_prv(skb)->skbcnt = 0;
 219
 220         skb_put_data(skb, &cf, sizeof(struct can_frame));
 221
 222         sl->dev->stats.rx_packets++;
 223         sl->dev->stats.rx_bytes += cf.can_dlc;
 224         netif_rx_ni(skb);
 225 }
 226
 227 /* parse tty input stream */
 228 static void slcan_unesc(struct slcan *sl, unsigned char s)
 229 {
 230         if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
 231                 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
 232                     (sl->rcount > 4))  {
 233                         slc_bump(sl);
 234                 }
 235                 sl->rcount = 0;
 236         } else {
 237                 if (!test_bit(SLF_ERROR, &sl->flags))  {
 238                         if (sl->rcount < SLC_MTU)  {
 239                                 sl->rbuff[sl->rcount++] = s;
 240                                 return;
 241                         } else {
 242                                 sl->dev->stats.rx_over_errors++;
 243                                 set_bit(SLF_ERROR, &sl->flags);
 244                         }
 245                 }
 246         }
 247 }
 248
 249  /************************************************************************
 250   *                     STANDARD SLCAN ENCAPSULATION                     *
 251   ************************************************************************/
 252
 253 /* Encapsulate one can_frame and stuff into a TTY queue. */
 254 static void slc_encaps(struct slcan *sl, struct can_frame *cf)
 255 {
 256         int actual, i;
 257         unsigned char *pos;
 258         unsigned char *endpos;
 259         canid_t id = cf->can_id;
 260
 261         pos = sl->xbuff;
 262
 263         if (cf->can_id & CAN_RTR_FLAG)
 264                 *pos = 'R'; /* becomes 'r' in standard frame format (SFF) */
 265         else
 266                 *pos = 'T'; /* becomes 't' in standard frame format (SSF) */
 267
 268         /* determine number of chars for the CAN-identifier */
 269         if (cf->can_id & CAN_EFF_FLAG) {
 270                 id &= CAN_EFF_MASK;
 271                 endpos = pos + SLC_EFF_ID_LEN;
 272         } else {
 273                 *pos |= 0x20; /* convert R/T to lower case for SFF */
 274                 id &= CAN_SFF_MASK;
 275                 endpos = pos + SLC_SFF_ID_LEN;
 276         }
 277
 278         /* build 3 (SFF) or 8 (EFF) digit CAN identifier */
 279         pos++;
 280         while (endpos >= pos) {
 281                 *endpos-- = hex_asc_upper[id & 0xf];
 282                 id >>= 4;
 283         }
 284
 285         pos += (cf->can_id & CAN_EFF_FLAG) ? SLC_EFF_ID_LEN : SLC_SFF_ID_LEN;
 286
 287         *pos++ = cf->can_dlc + '0';
 288
 289         /* RTR frames may have a dlc > 0 but they never have any data bytes */
 290         if (!(cf->can_id & CAN_RTR_FLAG)) {
 291                 for (i = 0; i < cf->can_dlc; i++)
 292                         pos = hex_byte_pack_upper(pos, cf->data[i]);
 293         }
 294
 295         *pos++ = '\r';
 296
 297         /* Order of next two lines is *very* important.
 298          * When we are sending a little amount of data,
 299          * the transfer may be completed inside the ops->write()
 300          * routine, because it's running with interrupts enabled.
 301          * In this case we *never* got WRITE_WAKEUP event,
 302          * if we did not request it before write operation.
 303          *       14 Oct 1994  Dmitry Gorodchanin.
 304          */
 305         set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 306         actual = sl->tty->ops->write(sl->tty, sl->xbuff, pos - sl->xbuff);
 307         sl->xleft = (pos - sl->xbuff) - actual;
 308         sl->xhead = sl->xbuff + actual;
 309         sl->dev->stats.tx_bytes += cf->can_dlc;
 310 }
 311
 312 /* Write out any remaining transmit buffer. Scheduled when tty is writable */
 313 static void slcan_transmit(struct work_struct *work)
 314 {
 315         struct slcan *sl = container_of(work, struct slcan, tx_work);
 316         int actual;
 317
 318         spin_lock_bh(&sl->lock);
 319         /* First make sure we're connected. */
 320         if (!sl->tty || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev)) {
 321                 spin_unlock_bh(&sl->lock);
 322                 return;
 323         }
 324
 325         if (sl->xleft <= 0)  {
 326                 /* Now serial buffer is almost free & we can start
 327                  * transmission of another packet */
 328                 sl->dev->stats.tx_packets++;
 329                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 330                 spin_unlock_bh(&sl->lock);
 331                 netif_wake_queue(sl->dev);
 332                 return;
 333         }
 334
 335         actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft);
 336         sl->xleft -= actual;
 337         sl->xhead += actual;
 338         spin_unlock_bh(&sl->lock);
 339 }
 340
 341 /*
 342  * Called by the driver when there's room for more data.
 343  * Schedule the transmit.
 344  */
 345 static void slcan_write_wakeup(struct tty_struct *tty)
 346 {
 347         struct slcan *sl;
 348
 349         rcu_read_lock();
 350         sl = rcu_dereference(tty->disc_data);
 351         if (!sl)
 352                 goto out;
 353
 354         schedule_work(&sl->tx_work);
 355 out:
 356         rcu_read_unlock();
 357 }
 358
 359 /* Send a can_frame to a TTY queue. */
 360 static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 361 {
 362         struct slcan *sl = netdev_priv(dev);
 363
 364         if (skb->len != CAN_MTU)
 365                 goto out;
 366
 367         spin_lock(&sl->lock);
 368         if (!netif_running(dev))  {
 369                 spin_unlock(&sl->lock);
 370                 printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
 371                 goto out;
 372         }
 373         if (sl->tty == NULL) {
 374                 spin_unlock(&sl->lock);
 375                 goto out;
 376         }
 377
 378         netif_stop_queue(sl->dev);
 379         slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
 380         spin_unlock(&sl->lock);
 381
 382 out:
 383         kfree_skb(skb);
 384         return NETDEV_TX_OK;
 385 }
 386
 387
 388 /******************************************
 389  *   Routines looking at netdevice side.
 390  ******************************************/
 391
 392 /* Netdevice UP -> DOWN routine */
 393 static int slc_close(struct net_device *dev)
 394 {
 395         struct slcan *sl = netdev_priv(dev);
 396
 397         spin_lock_bh(&sl->lock);
 398         if (sl->tty) {
 399                 /* TTY discipline is running. */
 400                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 401         }
 402         netif_stop_queue(dev);
 403         sl->rcount   = 0;
 404         sl->xleft    = 0;
 405         spin_unlock_bh(&sl->lock);
 406
 407         return 0;
 408 }
 409
 410 /* Netdevice DOWN -> UP routine */
 411 static int slc_open(struct net_device *dev)
 412 {
 413         struct slcan *sl = netdev_priv(dev);
 414
 415         if (sl->tty == NULL)
 416                 return -ENODEV;
 417
 418         sl->flags &= (1 << SLF_INUSE);
 419         netif_start_queue(dev);
 420         return 0;
 421 }
 422
 423 /* Hook the destructor so we can free slcan devs at the right point in time */
 424 static void slc_free_netdev(struct net_device *dev)
 425 {
 426         int i = dev->base_addr;
 427
 428         slcan_devs[i] = NULL;
 429 }
 430
 431 static int slcan_change_mtu(struct net_device *dev, int new_mtu)
 432 {
 433         return -EINVAL;
 434 }
 435
 436 static const struct net_device_ops slc_netdev_ops = {
 437         .ndo_open               = slc_open,
 438         .ndo_stop               = slc_close,
 439         .ndo_start_xmit         = slc_xmit,
 440         .ndo_change_mtu         = slcan_change_mtu,
 441 };
 442
 443 static void slc_setup(struct net_device *dev)
 444 {
 445         dev->netdev_ops         = &slc_netdev_ops;
 446         dev->needs_free_netdev  = true;
 447         dev->priv_destructor    = slc_free_netdev;
 448
 449         dev->hard_header_len    = 0;
 450         dev->addr_len           = 0;
 451         dev->tx_queue_len       = 10;
 452
 453         dev->mtu                = CAN_MTU;
 454         dev->type               = ARPHRD_CAN;
 455
 456         /* New-style flags. */
 457         dev->flags              = IFF_NOARP;
 458         dev->features           = NETIF_F_HW_CSUM;
 459 }
 460
 461 /******************************************
 462   Routines looking at TTY side.
 463  ******************************************/
 464
 465 /*
 466  * Handle the 'receiver data ready' interrupt.
 467  * This function is called by the 'tty_io' module in the kernel when
 468  * a block of SLCAN data has been received, which can now be decapsulated
 469  * and sent on to some IP layer for further processing. This will not
 470  * be re-entered while running but other ldisc functions may be called
 471  * in parallel
 472  */
 473
 474 static void slcan_receive_buf(struct tty_struct *tty,
 475                               const unsigned char *cp, char *fp, int count)
 476 {
 477         struct slcan *sl = (struct slcan *) tty->disc_data;
 478
 479         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 480                 return;
 481
 482         /* Read the characters out of the buffer */
 483         while (count--) {
 484                 if (fp && *fp++) {
 485                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
 486                                 sl->dev->stats.rx_errors++;
 487                         cp++;
 488                         continue;
 489                 }
 490                 slcan_unesc(sl, *cp++);
 491         }
 492 }
 493
 494 /************************************
 495  *  slcan_open helper routines.
 496  ************************************/
 497
 498 /* Collect hanged up channels */
 499 static void slc_sync(void)
 500 {
 501         int i;
 502         struct net_device *dev;
 503         struct slcan      *sl;
 504
 505         for (i = 0; i < maxdev; i++) {
 506                 dev = slcan_devs[i];
 507                 if (dev == NULL)
 508                         break;
 509
 510                 sl = netdev_priv(dev);
 511                 if (sl->tty)
 512                         continue;
 513                 if (dev->flags & IFF_UP)
 514                         dev_close(dev);
 515         }
 516 }
 517
 518 /* Find a free SLCAN channel, and link in this `tty' line. */
 519 static struct slcan *slc_alloc(void)
 520 {
 521         int i;
 522         char name[IFNAMSIZ];
 523         struct net_device *dev = NULL;
 524         struct slcan       *sl;
 525         int size;
 526
 527         for (i = 0; i < maxdev; i++) {
 528                 dev = slcan_devs[i];
 529                 if (dev == NULL)
 530                         break;
 531
 532         }
 533
 534         /* Sorry, too many, all slots in use */
 535         if (i >= maxdev)
 536                 return NULL;
 537
 538         sprintf(name, "slcan%d", i);
 539         size = ALIGN(sizeof(*sl), NETDEV_ALIGN) + sizeof(struct can_ml_priv);
 540         dev = alloc_netdev(size, name, NET_NAME_UNKNOWN, slc_setup);
 541         if (!dev)
 542                 return NULL;
 543
 544         dev->base_addr  = i;
 545         sl = netdev_priv(dev);
 546         dev->ml_priv = (void *)sl + ALIGN(sizeof(*sl), NETDEV_ALIGN);
 547
 548         /* Initialize channel control data */
 549         sl->magic = SLCAN_MAGIC;
 550         sl->dev = dev;
 551         spin_lock_init(&sl->lock);
 552         INIT_WORK(&sl->tx_work, slcan_transmit);
 553         slcan_devs[i] = dev;
 554
 555         return sl;
 556 }
 557
 558 /*
 559  * Open the high-level part of the SLCAN channel.
 560  * This function is called by the TTY module when the
 561  * SLCAN line discipline is called for.  Because we are
 562  * sure the tty line exists, we only have to link it to
 563  * a free SLCAN channel...
 564  *
 565  * Called in process context serialized from other ldisc calls.
 566  */
 567
 568 static int slcan_open(struct tty_struct *tty)
 569 {
 570         struct slcan *sl;
 571         int err;
 572
 573         if (!capable(CAP_NET_ADMIN))
 574                 return -EPERM;
 575
 576         if (tty->ops->write == NULL)
 577                 return -EOPNOTSUPP;
 578
 579         /* RTnetlink lock is misused here to serialize concurrent
 580            opens of slcan channels. There are better ways, but it is
 581            the simplest one.
 582          */
 583         rtnl_lock();
 584
 585         /* Collect hanged up channels. */
 586         slc_sync();
 587
 588         sl = tty->disc_data;
 589
 590         err = -EEXIST;
 591         /* First make sure we're not already connected. */
 592         if (sl && sl->magic == SLCAN_MAGIC)
 593                 goto err_exit;
 594
 595         /* OK.  Find a free SLCAN channel to use. */
 596         err = -ENFILE;
 597         sl = slc_alloc();
 598         if (sl == NULL)
 599                 goto err_exit;
 600
 601         sl->tty = tty;
 602         tty->disc_data = sl;
 603
 604         if (!test_bit(SLF_INUSE, &sl->flags)) {
 605                 /* Perform the low-level SLCAN initialization. */
 606                 sl->rcount   = 0;
 607                 sl->xleft    = 0;
 608
 609                 set_bit(SLF_INUSE, &sl->flags);
 610
 611                 err = register_netdevice(sl->dev);
 612                 if (err)
 613                         goto err_free_chan;
 614         }
 615
 616         /* Done.  We have linked the TTY line to a channel. */
 617         rtnl_unlock();
 618         tty->receive_room = 65536;      /* We don't flow control */
 619
 620         /* TTY layer expects 0 on success */
 621         return 0;
 622
 623 err_free_chan:
 624         sl->tty = NULL;
 625         tty->disc_data = NULL;
 626         clear_bit(SLF_INUSE, &sl->flags);
 627         slc_free_netdev(sl->dev);
 628         free_netdev(sl->dev);
 629
 630 err_exit:
 631         rtnl_unlock();
 632
 633         /* Count references from TTY module */
 634         return err;
 635 }
 636
 637 /*
 638  * Close down a SLCAN channel.
 639  * This means flushing out any pending queues, and then returning. This
 640  * call is serialized against other ldisc functions.
 641  *
 642  * We also use this method for a hangup event.
 643  */
 644
 645 static void slcan_close(struct tty_struct *tty)
 646 {
 647         struct slcan *sl = (struct slcan *) tty->disc_data;
 648
 649         /* First make sure we're connected. */
 650         if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
 651                 return;
 652
 653         spin_lock_bh(&sl->lock);
 654         rcu_assign_pointer(tty->disc_data, NULL);
 655         sl->tty = NULL;
 656         spin_unlock_bh(&sl->lock);
 657
 658         synchronize_rcu();
 659         flush_work(&sl->tx_work);
 660
 661         /* Flush network side */
 662         unregister_netdev(sl->dev);
 663         /* This will complete via sl_free_netdev */
 664 }
 665
 666 static int slcan_hangup(struct tty_struct *tty)
 667 {
 668         slcan_close(tty);
 669         return 0;
 670 }
 671
 672 /* Perform I/O control on an active SLCAN channel. */
 673 static int slcan_ioctl(struct tty_struct *tty, struct file *file,
 674                        unsigned int cmd, unsigned long arg)
 675 {
 676         struct slcan *sl = (struct slcan *) tty->disc_data;
 677         unsigned int tmp;
 678
 679         /* First make sure we're connected. */
 680         if (!sl || sl->magic != SLCAN_MAGIC)
 681                 return -EINVAL;
 682
 683         switch (cmd) {
 684         case SIOCGIFNAME:
 685                 tmp = strlen(sl->dev->name) + 1;
 686                 if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
 687                         return -EFAULT;
 688                 return 0;
 689
 690         case SIOCSIFHWADDR:
 691                 return -EINVAL;
 692
 693         default:
 694                 return tty_mode_ioctl(tty, file, cmd, arg);
 695         }
 696 }
 697
 698 static struct tty_ldisc_ops slc_ldisc = {
 699         .owner          = THIS_MODULE,
 700         .magic          = TTY_LDISC_MAGIC,
 701         .name           = "slcan",
 702         .open           = slcan_open,
 703         .close          = slcan_close,
 704         .hangup         = slcan_hangup,
 705         .ioctl          = slcan_ioctl,
 706         .receive_buf    = slcan_receive_buf,
 707         .write_wakeup   = slcan_write_wakeup,
 708 };
 709
 710 static int __init slcan_init(void)
 711 {
 712         int status;
 713
 714         if (maxdev < 4)
 715                 maxdev = 4; /* Sanity */
 716
 717         pr_info("slcan: serial line CAN interface driver\n");
 718         pr_info("slcan: %d dynamic interface channels.\n", maxdev);
 719
 720         slcan_devs = kcalloc(maxdev, sizeof(struct net_device *), GFP_KERNEL);
 721         if (!slcan_devs)
 722                 return -ENOMEM;
 723
 724         /* Fill in our line protocol discipline, and register it */
 725         status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
 726         if (status)  {
 727                 printk(KERN_ERR "slcan: can't register line discipline\n");
 728                 kfree(slcan_devs);
 729         }
 730         return status;
 731 }
 732
 733 static void __exit slcan_exit(void)
 734 {
 735         int i;
 736         struct net_device *dev;
 737         struct slcan *sl;
 738         unsigned long timeout = jiffies + HZ;
 739         int busy = 0;
 740
 741         if (slcan_devs == NULL)
 742                 return;
 743
 744         /* First of all: check for active disciplines and hangup them.
 745          */
 746         do {
 747                 if (busy)
 748                         msleep_interruptible(100);
 749
 750                 busy = 0;
 751                 for (i = 0; i < maxdev; i++) {
 752                         dev = slcan_devs[i];
 753                         if (!dev)
 754                                 continue;
 755                         sl = netdev_priv(dev);
 756                         spin_lock_bh(&sl->lock);
 757                         if (sl->tty) {
 758                                 busy++;
 759                                 tty_hangup(sl->tty);
 760                         }
 761                         spin_unlock_bh(&sl->lock);
 762                 }
 763         } while (busy && time_before(jiffies, timeout));
 764
 765         /* FIXME: hangup is async so we should wait when doing this second
 766            phase */
 767
 768         for (i = 0; i < maxdev; i++) {
 769                 dev = slcan_devs[i];
 770                 if (!dev)
 771                         continue;
 772                 slcan_devs[i] = NULL;
 773
 774                 sl = netdev_priv(dev);
 775                 if (sl->tty) {
 776                         printk(KERN_ERR "%s: tty discipline still running\n",
 777                                dev->name);
 778                 }
 779
 780                 unregister_netdev(dev);
 781         }
 782
 783         kfree(slcan_devs);
 784         slcan_devs = NULL;
 785
 786         i = tty_unregister_ldisc(N_SLCAN);
 787         if (i)
 788                 printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
 789 }
 790
 791 module_init(slcan_init);
 792 module_exit(slcan_exit);