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.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, write to the Free Software Foundation, Inc.,
  22  * 59 Temple Place, Suite 330, Boston, MA 02111-1307. You can also get it
  23  * at http://www.gnu.org/licenses/gpl.html
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  26  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  27  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  28  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  29  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  30  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  31  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  35  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  36  * DAMAGE.
  37  *
  38  * Send feedback to <socketcan-users@lists.berlios.de>
  39  *
  40  */
  41
  42 #include <linux/module.h>
  43 #include <linux/moduleparam.h>
  44
  45 #include <asm/system.h>
  46 #include <linux/uaccess.h>
  47 #include <linux/bitops.h>
  48 #include <linux/string.h>
  49 #include <linux/tty.h>
  50 #include <linux/errno.h>
  51 #include <linux/netdevice.h>
  52 #include <linux/skbuff.h>
  53 #include <linux/rtnetlink.h>
  54 #include <linux/if_arp.h>
  55 #include <linux/if_ether.h>
  56 #include <linux/sched.h>
  57 #include <linux/delay.h>
  58 #include <linux/init.h>
  59 #include <linux/kernel.h>
  60 #include <linux/can.h>
  61
  62 static __initdata const char banner[] =
  63         KERN_INFO "slcan: serial line CAN interface driver\n";
  64
  65 MODULE_ALIAS_LDISC(N_SLCAN);
  66 MODULE_DESCRIPTION("serial line CAN interface");
  67 MODULE_LICENSE("GPL");
  68 MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
  69
  70 #define SLCAN_MAGIC 0x53CA
  71
  72 static int maxdev = 10;         /* MAX number of SLCAN channels;
  73                                    This can be overridden with
  74                                    insmod slcan.ko maxdev=nnn   */
  75 module_param(maxdev, int, 0);
  76 MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
  77
  78 /* maximum rx buffer len: extended CAN frame with timestamp */
  79 #define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
  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, dlc_pos, tmp;
 148         unsigned long ultmp;
 149         char cmd = sl->rbuff[0];
 150
 151         if ((cmd != 't') && (cmd != 'T') && (cmd != 'r') && (cmd != 'R'))
 152                 return;
 153
 154         if (cmd & 0x20) /* tiny chars 'r' 't' => standard frame format */
 155                 dlc_pos = 4; /* dlc position tiiid */
 156         else
 157                 dlc_pos = 9; /* dlc position Tiiiiiiiid */
 158
 159         if (!((sl->rbuff[dlc_pos] >= '0') && (sl->rbuff[dlc_pos] < '9')))
 160                 return;
 161
 162         cf.can_dlc = sl->rbuff[dlc_pos] - '0'; /* get can_dlc from ASCII val */
 163
 164         sl->rbuff[dlc_pos] = 0; /* terminate can_id string */
 165
 166         if (strict_strtoul(sl->rbuff+1, 16, &ultmp))
 167                 return;
 168
 169         cf.can_id = ultmp;
 170
 171         if (!(cmd & 0x20)) /* NO tiny chars => extended frame format */
 172                 cf.can_id |= CAN_EFF_FLAG;
 173
 174         if ((cmd | 0x20) == 'r') /* RTR frame */
 175                 cf.can_id |= CAN_RTR_FLAG;
 176
 177         *(u64 *) (&cf.data) = 0; /* clear payload */
 178
 179         for (i = 0, dlc_pos++; i < cf.can_dlc; i++) {
 180                 tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
 181                 if (tmp < 0)
 182                         return;
 183                 cf.data[i] = (tmp << 4);
 184                 tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
 185                 if (tmp < 0)
 186                         return;
 187                 cf.data[i] |= tmp;
 188         }
 189
 190         skb = dev_alloc_skb(sizeof(struct can_frame));
 191         if (!skb)
 192                 return;
 193
 194         skb->dev = sl->dev;
 195         skb->protocol = htons(ETH_P_CAN);
 196         skb->pkt_type = PACKET_BROADCAST;
 197         skb->ip_summed = CHECKSUM_UNNECESSARY;
 198         memcpy(skb_put(skb, sizeof(struct can_frame)),
 199                &cf, sizeof(struct can_frame));
 200         netif_rx_ni(skb);
 201
 202         sl->dev->stats.rx_packets++;
 203         sl->dev->stats.rx_bytes += cf.can_dlc;
 204 }
 205
 206 /* parse tty input stream */
 207 static void slcan_unesc(struct slcan *sl, unsigned char s)
 208 {
 209
 210         if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
 211                 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
 212                     (sl->rcount > 4))  {
 213                         slc_bump(sl);
 214                 }
 215                 sl->rcount = 0;
 216         } else {
 217                 if (!test_bit(SLF_ERROR, &sl->flags))  {
 218                         if (sl->rcount < SLC_MTU)  {
 219                                 sl->rbuff[sl->rcount++] = s;
 220                                 return;
 221                         } else {
 222                                 sl->dev->stats.rx_over_errors++;
 223                                 set_bit(SLF_ERROR, &sl->flags);
 224                         }
 225                 }
 226         }
 227 }
 228
 229  /************************************************************************
 230   *                     STANDARD SLCAN ENCAPSULATION                     *
 231   ************************************************************************/
 232
 233 /* Encapsulate one can_frame and stuff into a TTY queue. */
 234 static void slc_encaps(struct slcan *sl, struct can_frame *cf)
 235 {
 236         int actual, idx, i;
 237         char cmd;
 238
 239         if (cf->can_id & CAN_RTR_FLAG)
 240                 cmd = 'R'; /* becomes 'r' in standard frame format */
 241         else
 242                 cmd = 'T'; /* becomes 't' in standard frame format */
 243
 244         if (cf->can_id & CAN_EFF_FLAG)
 245                 sprintf(sl->xbuff, "%c%08X%d", cmd,
 246                         cf->can_id & CAN_EFF_MASK, cf->can_dlc);
 247         else
 248                 sprintf(sl->xbuff, "%c%03X%d", cmd | 0x20,
 249                         cf->can_id & CAN_SFF_MASK, cf->can_dlc);
 250
 251         idx = strlen(sl->xbuff);
 252
 253         for (i = 0; i < cf->can_dlc; i++)
 254                 sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);
 255
 256         strcat(sl->xbuff, "\r"); /* add terminating character */
 257
 258         /* Order of next two lines is *very* important.
 259          * When we are sending a little amount of data,
 260          * the transfer may be completed inside the ops->write()
 261          * routine, because it's running with interrupts enabled.
 262          * In this case we *never* got WRITE_WAKEUP event,
 263          * if we did not request it before write operation.
 264          *       14 Oct 1994  Dmitry Gorodchanin.
 265          */
 266         set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 267         actual = sl->tty->ops->write(sl->tty, sl->xbuff, strlen(sl->xbuff));
 268         sl->xleft = strlen(sl->xbuff) - actual;
 269         sl->xhead = sl->xbuff + actual;
 270         sl->dev->stats.tx_bytes += cf->can_dlc;
 271 }
 272
 273 /*
 274  * Called by the driver when there's room for more data.  If we have
 275  * more packets to send, we send them here.
 276  */
 277 static void slcan_write_wakeup(struct tty_struct *tty)
 278 {
 279         int actual;
 280         struct slcan *sl = (struct slcan *) tty->disc_data;
 281
 282         /* First make sure we're connected. */
 283         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 284                 return;
 285
 286         if (sl->xleft <= 0)  {
 287                 /* Now serial buffer is almost free & we can start
 288                  * transmission of another packet */
 289                 sl->dev->stats.tx_packets++;
 290                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 291                 netif_wake_queue(sl->dev);
 292                 return;
 293         }
 294
 295         actual = tty->ops->write(tty, sl->xhead, sl->xleft);
 296         sl->xleft -= actual;
 297         sl->xhead += actual;
 298 }
 299
 300 /* Send a can_frame to a TTY queue. */
 301 static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 302 {
 303         struct slcan *sl = netdev_priv(dev);
 304
 305         if (skb->len != sizeof(struct can_frame))
 306                 goto out;
 307
 308         spin_lock(&sl->lock);
 309         if (!netif_running(dev))  {
 310                 spin_unlock(&sl->lock);
 311                 printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
 312                 goto out;
 313         }
 314         if (sl->tty == NULL) {
 315                 spin_unlock(&sl->lock);
 316                 goto out;
 317         }
 318
 319         netif_stop_queue(sl->dev);
 320         slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
 321         spin_unlock(&sl->lock);
 322
 323 out:
 324         kfree_skb(skb);
 325         return NETDEV_TX_OK;
 326 }
 327
 328
 329 /******************************************
 330  *   Routines looking at netdevice side.
 331  ******************************************/
 332
 333 /* Netdevice UP -> DOWN routine */
 334 static int slc_close(struct net_device *dev)
 335 {
 336         struct slcan *sl = netdev_priv(dev);
 337
 338         spin_lock_bh(&sl->lock);
 339         if (sl->tty) {
 340                 /* TTY discipline is running. */
 341                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 342         }
 343         netif_stop_queue(dev);
 344         sl->rcount   = 0;
 345         sl->xleft    = 0;
 346         spin_unlock_bh(&sl->lock);
 347
 348         return 0;
 349 }
 350
 351 /* Netdevice DOWN -> UP routine */
 352 static int slc_open(struct net_device *dev)
 353 {
 354         struct slcan *sl = netdev_priv(dev);
 355
 356         if (sl->tty == NULL)
 357                 return -ENODEV;
 358
 359         sl->flags &= (1 << SLF_INUSE);
 360         netif_start_queue(dev);
 361         return 0;
 362 }
 363
 364 /* Hook the destructor so we can free slcan devs at the right point in time */
 365 static void slc_free_netdev(struct net_device *dev)
 366 {
 367         int i = dev->base_addr;
 368         free_netdev(dev);
 369         slcan_devs[i] = NULL;
 370 }
 371
 372 static const struct net_device_ops slc_netdev_ops = {
 373         .ndo_open               = slc_open,
 374         .ndo_stop               = slc_close,
 375         .ndo_start_xmit         = slc_xmit,
 376 };
 377
 378 static void slc_setup(struct net_device *dev)
 379 {
 380         dev->netdev_ops         = &slc_netdev_ops;
 381         dev->destructor         = slc_free_netdev;
 382
 383         dev->hard_header_len    = 0;
 384         dev->addr_len           = 0;
 385         dev->tx_queue_len       = 10;
 386
 387         dev->mtu                = sizeof(struct can_frame);
 388         dev->type               = ARPHRD_CAN;
 389
 390         /* New-style flags. */
 391         dev->flags              = IFF_NOARP;
 392         dev->features           = NETIF_F_NO_CSUM;
 393 }
 394
 395 /******************************************
 396   Routines looking at TTY side.
 397  ******************************************/
 398
 399 /*
 400  * Handle the 'receiver data ready' interrupt.
 401  * This function is called by the 'tty_io' module in the kernel when
 402  * a block of SLCAN data has been received, which can now be decapsulated
 403  * and sent on to some IP layer for further processing. This will not
 404  * be re-entered while running but other ldisc functions may be called
 405  * in parallel
 406  */
 407
 408 static void slcan_receive_buf(struct tty_struct *tty,
 409                               const unsigned char *cp, char *fp, int count)
 410 {
 411         struct slcan *sl = (struct slcan *) tty->disc_data;
 412
 413         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 414                 return;
 415
 416         /* Read the characters out of the buffer */
 417         while (count--) {
 418                 if (fp && *fp++) {
 419                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
 420                                 sl->dev->stats.rx_errors++;
 421                         cp++;
 422                         continue;
 423                 }
 424                 slcan_unesc(sl, *cp++);
 425         }
 426 }
 427
 428 /************************************
 429  *  slcan_open helper routines.
 430  ************************************/
 431
 432 /* Collect hanged up channels */
 433 static void slc_sync(void)
 434 {
 435         int i;
 436         struct net_device *dev;
 437         struct slcan      *sl;
 438
 439         for (i = 0; i < maxdev; i++) {
 440                 dev = slcan_devs[i];
 441                 if (dev == NULL)
 442                         break;
 443
 444                 sl = netdev_priv(dev);
 445                 if (sl->tty)
 446                         continue;
 447                 if (dev->flags & IFF_UP)
 448                         dev_close(dev);
 449         }
 450 }
 451
 452 /* Find a free SLCAN channel, and link in this `tty' line. */
 453 static struct slcan *slc_alloc(dev_t line)
 454 {
 455         int i;
 456         char name[IFNAMSIZ];
 457         struct net_device *dev = NULL;
 458         struct slcan       *sl;
 459
 460         for (i = 0; i < maxdev; i++) {
 461                 dev = slcan_devs[i];
 462                 if (dev == NULL)
 463                         break;
 464
 465         }
 466
 467         /* Sorry, too many, all slots in use */
 468         if (i >= maxdev)
 469                 return NULL;
 470
 471         sprintf(name, "slcan%d", i);
 472         dev = alloc_netdev(sizeof(*sl), name, slc_setup);
 473         if (!dev)
 474                 return NULL;
 475
 476         dev->base_addr  = i;
 477         sl = netdev_priv(dev);
 478
 479         /* Initialize channel control data */
 480         sl->magic = SLCAN_MAGIC;
 481         sl->dev = dev;
 482         spin_lock_init(&sl->lock);
 483         slcan_devs[i] = dev;
 484
 485         return sl;
 486 }
 487
 488 /*
 489  * Open the high-level part of the SLCAN channel.
 490  * This function is called by the TTY module when the
 491  * SLCAN line discipline is called for.  Because we are
 492  * sure the tty line exists, we only have to link it to
 493  * a free SLCAN channel...
 494  *
 495  * Called in process context serialized from other ldisc calls.
 496  */
 497
 498 static int slcan_open(struct tty_struct *tty)
 499 {
 500         struct slcan *sl;
 501         int err;
 502
 503         if (!capable(CAP_NET_ADMIN))
 504                 return -EPERM;
 505
 506         if (tty->ops->write == NULL)
 507                 return -EOPNOTSUPP;
 508
 509         /* RTnetlink lock is misused here to serialize concurrent
 510            opens of slcan channels. There are better ways, but it is
 511            the simplest one.
 512          */
 513         rtnl_lock();
 514
 515         /* Collect hanged up channels. */
 516         slc_sync();
 517
 518         sl = tty->disc_data;
 519
 520         err = -EEXIST;
 521         /* First make sure we're not already connected. */
 522         if (sl && sl->magic == SLCAN_MAGIC)
 523                 goto err_exit;
 524
 525         /* OK.  Find a free SLCAN channel to use. */
 526         err = -ENFILE;
 527         sl = slc_alloc(tty_devnum(tty));
 528         if (sl == NULL)
 529                 goto err_exit;
 530
 531         sl->tty = tty;
 532         tty->disc_data = sl;
 533
 534         if (!test_bit(SLF_INUSE, &sl->flags)) {
 535                 /* Perform the low-level SLCAN initialization. */
 536                 sl->rcount   = 0;
 537                 sl->xleft    = 0;
 538
 539                 set_bit(SLF_INUSE, &sl->flags);
 540
 541                 err = register_netdevice(sl->dev);
 542                 if (err)
 543                         goto err_free_chan;
 544         }
 545
 546         /* Done.  We have linked the TTY line to a channel. */
 547         rtnl_unlock();
 548         tty->receive_room = 65536;      /* We don't flow control */
 549
 550         /* TTY layer expects 0 on success */
 551         return 0;
 552
 553 err_free_chan:
 554         sl->tty = NULL;
 555         tty->disc_data = NULL;
 556         clear_bit(SLF_INUSE, &sl->flags);
 557
 558 err_exit:
 559         rtnl_unlock();
 560
 561         /* Count references from TTY module */
 562         return err;
 563 }
 564
 565 /*
 566  * Close down a SLCAN channel.
 567  * This means flushing out any pending queues, and then returning. This
 568  * call is serialized against other ldisc functions.
 569  *
 570  * We also use this method for a hangup event.
 571  */
 572
 573 static void slcan_close(struct tty_struct *tty)
 574 {
 575         struct slcan *sl = (struct slcan *) tty->disc_data;
 576
 577         /* First make sure we're connected. */
 578         if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
 579                 return;
 580
 581         tty->disc_data = NULL;
 582         sl->tty = NULL;
 583
 584         /* Flush network side */
 585         unregister_netdev(sl->dev);
 586         /* This will complete via sl_free_netdev */
 587 }
 588
 589 static int slcan_hangup(struct tty_struct *tty)
 590 {
 591         slcan_close(tty);
 592         return 0;
 593 }
 594
 595 /* Perform I/O control on an active SLCAN channel. */
 596 static int slcan_ioctl(struct tty_struct *tty, struct file *file,
 597                        unsigned int cmd, unsigned long arg)
 598 {
 599         struct slcan *sl = (struct slcan *) tty->disc_data;
 600         unsigned int tmp;
 601
 602         /* First make sure we're connected. */
 603         if (!sl || sl->magic != SLCAN_MAGIC)
 604                 return -EINVAL;
 605
 606         switch (cmd) {
 607         case SIOCGIFNAME:
 608                 tmp = strlen(sl->dev->name) + 1;
 609                 if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
 610                         return -EFAULT;
 611                 return 0;
 612
 613         case SIOCSIFHWADDR:
 614                 return -EINVAL;
 615
 616         default:
 617                 return tty_mode_ioctl(tty, file, cmd, arg);
 618         }
 619 }
 620
 621 static struct tty_ldisc_ops slc_ldisc = {
 622         .owner          = THIS_MODULE,
 623         .magic          = TTY_LDISC_MAGIC,
 624         .name           = "slcan",
 625         .open           = slcan_open,
 626         .close          = slcan_close,
 627         .hangup         = slcan_hangup,
 628         .ioctl          = slcan_ioctl,
 629         .receive_buf    = slcan_receive_buf,
 630         .write_wakeup   = slcan_write_wakeup,
 631 };
 632
 633 static int __init slcan_init(void)
 634 {
 635         int status;
 636
 637         if (maxdev < 4)
 638                 maxdev = 4; /* Sanity */
 639
 640         printk(banner);
 641         printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
 642
 643         slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
 644         if (!slcan_devs) {
 645                 printk(KERN_ERR "slcan: can't allocate slcan device array!\n");
 646                 return -ENOMEM;
 647         }
 648
 649         /* Fill in our line protocol discipline, and register it */
 650         status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
 651         if (status)  {
 652                 printk(KERN_ERR "slcan: can't register line discipline\n");
 653                 kfree(slcan_devs);
 654         }
 655         return status;
 656 }
 657
 658 static void __exit slcan_exit(void)
 659 {
 660         int i;
 661         struct net_device *dev;
 662         struct slcan *sl;
 663         unsigned long timeout = jiffies + HZ;
 664         int busy = 0;
 665
 666         if (slcan_devs == NULL)
 667                 return;
 668
 669         /* First of all: check for active disciplines and hangup them.
 670          */
 671         do {
 672                 if (busy)
 673                         msleep_interruptible(100);
 674
 675                 busy = 0;
 676                 for (i = 0; i < maxdev; i++) {
 677                         dev = slcan_devs[i];
 678                         if (!dev)
 679                                 continue;
 680                         sl = netdev_priv(dev);
 681                         spin_lock_bh(&sl->lock);
 682                         if (sl->tty) {
 683                                 busy++;
 684                                 tty_hangup(sl->tty);
 685                         }
 686                         spin_unlock_bh(&sl->lock);
 687                 }
 688         } while (busy && time_before(jiffies, timeout));
 689
 690         /* FIXME: hangup is async so we should wait when doing this second
 691            phase */
 692
 693         for (i = 0; i < maxdev; i++) {
 694                 dev = slcan_devs[i];
 695                 if (!dev)
 696                         continue;
 697                 slcan_devs[i] = NULL;
 698
 699                 sl = netdev_priv(dev);
 700                 if (sl->tty) {
 701                         printk(KERN_ERR "%s: tty discipline still running\n",
 702                                dev->name);
 703                         /* Intentionally leak the control block. */
 704                         dev->destructor = NULL;
 705                 }
 706
 707                 unregister_netdev(dev);
 708         }
 709
 710         kfree(slcan_devs);
 711         slcan_devs = NULL;
 712
 713         i = tty_unregister_ldisc(N_SLCAN);
 714         if (i)
 715                 printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
 716 }
 717
 718 module_init(slcan_init);
 719 module_exit(slcan_exit);