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/can.h>
  56 #include <linux/can/skb.h>
  57
  58 static __initconst const char banner[] =
  59         KERN_INFO "slcan: serial line CAN interface driver\n";
  60
  61 MODULE_ALIAS_LDISC(N_SLCAN);
  62 MODULE_DESCRIPTION("serial line CAN interface");
  63 MODULE_LICENSE("GPL");
  64 MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
  65
  66 #define SLCAN_MAGIC 0x53CA
  67
  68 static int maxdev = 10;         /* MAX number of SLCAN channels;
  69                                    This can be overridden with
  70                                    insmod slcan.ko maxdev=nnn   */
  71 module_param(maxdev, int, 0);
  72 MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
  73
  74 /* maximum rx buffer len: extended CAN frame with timestamp */
  75 #define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
  76
  77 #define SLC_CMD_LEN 1
  78 #define SLC_SFF_ID_LEN 3
  79 #define SLC_EFF_ID_LEN 8
  80
  81 struct slcan {
  82         int                     magic;
  83
  84         /* Various fields. */
  85         struct tty_struct       *tty;           /* ptr to TTY structure      */
  86         struct net_device       *dev;           /* easy for intr handling    */
  87         spinlock_t              lock;
  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
 219         memcpy(skb_put(skb, sizeof(struct can_frame)),
 220                &cf, sizeof(struct can_frame));
 221         netif_rx_ni(skb);
 222
 223         sl->dev->stats.rx_packets++;
 224         sl->dev->stats.rx_bytes += cf.can_dlc;
 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 /*
 313  * Called by the driver when there's room for more data.  If we have
 314  * more packets to send, we send them here.
 315  */
 316 static void slcan_write_wakeup(struct tty_struct *tty)
 317 {
 318         int actual;
 319         struct slcan *sl = (struct slcan *) tty->disc_data;
 320
 321         /* First make sure we're connected. */
 322         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 323                 return;
 324
 325         spin_lock(&sl->lock);
 326         if (sl->xleft <= 0)  {
 327                 /* Now serial buffer is almost free & we can start
 328                  * transmission of another packet */
 329                 sl->dev->stats.tx_packets++;
 330                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 331                 spin_unlock(&sl->lock);
 332                 netif_wake_queue(sl->dev);
 333                 return;
 334         }
 335
 336         actual = tty->ops->write(tty, sl->xhead, sl->xleft);
 337         sl->xleft -= actual;
 338         sl->xhead += actual;
 339         spin_unlock(&sl->lock);
 340 }
 341
 342 /* Send a can_frame to a TTY queue. */
 343 static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 344 {
 345         struct slcan *sl = netdev_priv(dev);
 346
 347         if (skb->len != sizeof(struct can_frame))
 348                 goto out;
 349
 350         spin_lock(&sl->lock);
 351         if (!netif_running(dev))  {
 352                 spin_unlock(&sl->lock);
 353                 printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
 354                 goto out;
 355         }
 356         if (sl->tty == NULL) {
 357                 spin_unlock(&sl->lock);
 358                 goto out;
 359         }
 360
 361         netif_stop_queue(sl->dev);
 362         slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
 363         spin_unlock(&sl->lock);
 364
 365 out:
 366         kfree_skb(skb);
 367         return NETDEV_TX_OK;
 368 }
 369
 370
 371 /******************************************
 372  *   Routines looking at netdevice side.
 373  ******************************************/
 374
 375 /* Netdevice UP -> DOWN routine */
 376 static int slc_close(struct net_device *dev)
 377 {
 378         struct slcan *sl = netdev_priv(dev);
 379
 380         spin_lock_bh(&sl->lock);
 381         if (sl->tty) {
 382                 /* TTY discipline is running. */
 383                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 384         }
 385         netif_stop_queue(dev);
 386         sl->rcount   = 0;
 387         sl->xleft    = 0;
 388         spin_unlock_bh(&sl->lock);
 389
 390         return 0;
 391 }
 392
 393 /* Netdevice DOWN -> UP routine */
 394 static int slc_open(struct net_device *dev)
 395 {
 396         struct slcan *sl = netdev_priv(dev);
 397
 398         if (sl->tty == NULL)
 399                 return -ENODEV;
 400
 401         sl->flags &= (1 << SLF_INUSE);
 402         netif_start_queue(dev);
 403         return 0;
 404 }
 405
 406 /* Hook the destructor so we can free slcan devs at the right point in time */
 407 static void slc_free_netdev(struct net_device *dev)
 408 {
 409         int i = dev->base_addr;
 410         free_netdev(dev);
 411         slcan_devs[i] = NULL;
 412 }
 413
 414 static const struct net_device_ops slc_netdev_ops = {
 415         .ndo_open               = slc_open,
 416         .ndo_stop               = slc_close,
 417         .ndo_start_xmit         = slc_xmit,
 418 };
 419
 420 static void slc_setup(struct net_device *dev)
 421 {
 422         dev->netdev_ops         = &slc_netdev_ops;
 423         dev->destructor         = slc_free_netdev;
 424
 425         dev->hard_header_len    = 0;
 426         dev->addr_len           = 0;
 427         dev->tx_queue_len       = 10;
 428
 429         dev->mtu                = sizeof(struct can_frame);
 430         dev->type               = ARPHRD_CAN;
 431
 432         /* New-style flags. */
 433         dev->flags              = IFF_NOARP;
 434         dev->features           = NETIF_F_HW_CSUM;
 435 }
 436
 437 /******************************************
 438   Routines looking at TTY side.
 439  ******************************************/
 440
 441 /*
 442  * Handle the 'receiver data ready' interrupt.
 443  * This function is called by the 'tty_io' module in the kernel when
 444  * a block of SLCAN data has been received, which can now be decapsulated
 445  * and sent on to some IP layer for further processing. This will not
 446  * be re-entered while running but other ldisc functions may be called
 447  * in parallel
 448  */
 449
 450 static void slcan_receive_buf(struct tty_struct *tty,
 451                               const unsigned char *cp, char *fp, int count)
 452 {
 453         struct slcan *sl = (struct slcan *) tty->disc_data;
 454
 455         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 456                 return;
 457
 458         /* Read the characters out of the buffer */
 459         while (count--) {
 460                 if (fp && *fp++) {
 461                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
 462                                 sl->dev->stats.rx_errors++;
 463                         cp++;
 464                         continue;
 465                 }
 466                 slcan_unesc(sl, *cp++);
 467         }
 468 }
 469
 470 /************************************
 471  *  slcan_open helper routines.
 472  ************************************/
 473
 474 /* Collect hanged up channels */
 475 static void slc_sync(void)
 476 {
 477         int i;
 478         struct net_device *dev;
 479         struct slcan      *sl;
 480
 481         for (i = 0; i < maxdev; i++) {
 482                 dev = slcan_devs[i];
 483                 if (dev == NULL)
 484                         break;
 485
 486                 sl = netdev_priv(dev);
 487                 if (sl->tty)
 488                         continue;
 489                 if (dev->flags & IFF_UP)
 490                         dev_close(dev);
 491         }
 492 }
 493
 494 /* Find a free SLCAN channel, and link in this `tty' line. */
 495 static struct slcan *slc_alloc(dev_t line)
 496 {
 497         int i;
 498         char name[IFNAMSIZ];
 499         struct net_device *dev = NULL;
 500         struct slcan       *sl;
 501
 502         for (i = 0; i < maxdev; i++) {
 503                 dev = slcan_devs[i];
 504                 if (dev == NULL)
 505                         break;
 506
 507         }
 508
 509         /* Sorry, too many, all slots in use */
 510         if (i >= maxdev)
 511                 return NULL;
 512
 513         sprintf(name, "slcan%d", i);
 514         dev = alloc_netdev(sizeof(*sl), name, slc_setup);
 515         if (!dev)
 516                 return NULL;
 517
 518         dev->base_addr  = i;
 519         sl = netdev_priv(dev);
 520
 521         /* Initialize channel control data */
 522         sl->magic = SLCAN_MAGIC;
 523         sl->dev = dev;
 524         spin_lock_init(&sl->lock);
 525         slcan_devs[i] = dev;
 526
 527         return sl;
 528 }
 529
 530 /*
 531  * Open the high-level part of the SLCAN channel.
 532  * This function is called by the TTY module when the
 533  * SLCAN line discipline is called for.  Because we are
 534  * sure the tty line exists, we only have to link it to
 535  * a free SLCAN channel...
 536  *
 537  * Called in process context serialized from other ldisc calls.
 538  */
 539
 540 static int slcan_open(struct tty_struct *tty)
 541 {
 542         struct slcan *sl;
 543         int err;
 544
 545         if (!capable(CAP_NET_ADMIN))
 546                 return -EPERM;
 547
 548         if (tty->ops->write == NULL)
 549                 return -EOPNOTSUPP;
 550
 551         /* RTnetlink lock is misused here to serialize concurrent
 552            opens of slcan channels. There are better ways, but it is
 553            the simplest one.
 554          */
 555         rtnl_lock();
 556
 557         /* Collect hanged up channels. */
 558         slc_sync();
 559
 560         sl = tty->disc_data;
 561
 562         err = -EEXIST;
 563         /* First make sure we're not already connected. */
 564         if (sl && sl->magic == SLCAN_MAGIC)
 565                 goto err_exit;
 566
 567         /* OK.  Find a free SLCAN channel to use. */
 568         err = -ENFILE;
 569         sl = slc_alloc(tty_devnum(tty));
 570         if (sl == NULL)
 571                 goto err_exit;
 572
 573         sl->tty = tty;
 574         tty->disc_data = sl;
 575
 576         if (!test_bit(SLF_INUSE, &sl->flags)) {
 577                 /* Perform the low-level SLCAN initialization. */
 578                 sl->rcount   = 0;
 579                 sl->xleft    = 0;
 580
 581                 set_bit(SLF_INUSE, &sl->flags);
 582
 583                 err = register_netdevice(sl->dev);
 584                 if (err)
 585                         goto err_free_chan;
 586         }
 587
 588         /* Done.  We have linked the TTY line to a channel. */
 589         rtnl_unlock();
 590         tty->receive_room = 65536;      /* We don't flow control */
 591
 592         /* TTY layer expects 0 on success */
 593         return 0;
 594
 595 err_free_chan:
 596         sl->tty = NULL;
 597         tty->disc_data = NULL;
 598         clear_bit(SLF_INUSE, &sl->flags);
 599
 600 err_exit:
 601         rtnl_unlock();
 602
 603         /* Count references from TTY module */
 604         return err;
 605 }
 606
 607 /*
 608  * Close down a SLCAN channel.
 609  * This means flushing out any pending queues, and then returning. This
 610  * call is serialized against other ldisc functions.
 611  *
 612  * We also use this method for a hangup event.
 613  */
 614
 615 static void slcan_close(struct tty_struct *tty)
 616 {
 617         struct slcan *sl = (struct slcan *) tty->disc_data;
 618
 619         /* First make sure we're connected. */
 620         if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
 621                 return;
 622
 623         tty->disc_data = NULL;
 624         sl->tty = NULL;
 625
 626         /* Flush network side */
 627         unregister_netdev(sl->dev);
 628         /* This will complete via sl_free_netdev */
 629 }
 630
 631 static int slcan_hangup(struct tty_struct *tty)
 632 {
 633         slcan_close(tty);
 634         return 0;
 635 }
 636
 637 /* Perform I/O control on an active SLCAN channel. */
 638 static int slcan_ioctl(struct tty_struct *tty, struct file *file,
 639                        unsigned int cmd, unsigned long arg)
 640 {
 641         struct slcan *sl = (struct slcan *) tty->disc_data;
 642         unsigned int tmp;
 643
 644         /* First make sure we're connected. */
 645         if (!sl || sl->magic != SLCAN_MAGIC)
 646                 return -EINVAL;
 647
 648         switch (cmd) {
 649         case SIOCGIFNAME:
 650                 tmp = strlen(sl->dev->name) + 1;
 651                 if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
 652                         return -EFAULT;
 653                 return 0;
 654
 655         case SIOCSIFHWADDR:
 656                 return -EINVAL;
 657
 658         default:
 659                 return tty_mode_ioctl(tty, file, cmd, arg);
 660         }
 661 }
 662
 663 static struct tty_ldisc_ops slc_ldisc = {
 664         .owner          = THIS_MODULE,
 665         .magic          = TTY_LDISC_MAGIC,
 666         .name           = "slcan",
 667         .open           = slcan_open,
 668         .close          = slcan_close,
 669         .hangup         = slcan_hangup,
 670         .ioctl          = slcan_ioctl,
 671         .receive_buf    = slcan_receive_buf,
 672         .write_wakeup   = slcan_write_wakeup,
 673 };
 674
 675 static int __init slcan_init(void)
 676 {
 677         int status;
 678
 679         if (maxdev < 4)
 680                 maxdev = 4; /* Sanity */
 681
 682         printk(banner);
 683         printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
 684
 685         slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
 686         if (!slcan_devs)
 687                 return -ENOMEM;
 688
 689         /* Fill in our line protocol discipline, and register it */
 690         status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
 691         if (status)  {
 692                 printk(KERN_ERR "slcan: can't register line discipline\n");
 693                 kfree(slcan_devs);
 694         }
 695         return status;
 696 }
 697
 698 static void __exit slcan_exit(void)
 699 {
 700         int i;
 701         struct net_device *dev;
 702         struct slcan *sl;
 703         unsigned long timeout = jiffies + HZ;
 704         int busy = 0;
 705
 706         if (slcan_devs == NULL)
 707                 return;
 708
 709         /* First of all: check for active disciplines and hangup them.
 710          */
 711         do {
 712                 if (busy)
 713                         msleep_interruptible(100);
 714
 715                 busy = 0;
 716                 for (i = 0; i < maxdev; i++) {
 717                         dev = slcan_devs[i];
 718                         if (!dev)
 719                                 continue;
 720                         sl = netdev_priv(dev);
 721                         spin_lock_bh(&sl->lock);
 722                         if (sl->tty) {
 723                                 busy++;
 724                                 tty_hangup(sl->tty);
 725                         }
 726                         spin_unlock_bh(&sl->lock);
 727                 }
 728         } while (busy && time_before(jiffies, timeout));
 729
 730         /* FIXME: hangup is async so we should wait when doing this second
 731            phase */
 732
 733         for (i = 0; i < maxdev; i++) {
 734                 dev = slcan_devs[i];
 735                 if (!dev)
 736                         continue;
 737                 slcan_devs[i] = NULL;
 738
 739                 sl = netdev_priv(dev);
 740                 if (sl->tty) {
 741                         printk(KERN_ERR "%s: tty discipline still running\n",
 742                                dev->name);
 743                         /* Intentionally leak the control block. */
 744                         dev->destructor = NULL;
 745                 }
 746
 747                 unregister_netdev(dev);
 748         }
 749
 750         kfree(slcan_devs);
 751         slcan_devs = NULL;
 752
 753         i = tty_unregister_ldisc(N_SLCAN);
 754         if (i)
 755                 printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
 756 }
 757
 758 module_init(slcan_init);
 759 module_exit(slcan_exit);