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, 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  */
  39
  40 #include <linux/module.h>
  41 #include <linux/moduleparam.h>
  42
  43 #include <linux/uaccess.h>
  44 #include <linux/bitops.h>
  45 #include <linux/string.h>
  46 #include <linux/tty.h>
  47 #include <linux/errno.h>
  48 #include <linux/netdevice.h>
  49 #include <linux/skbuff.h>
  50 #include <linux/rtnetlink.h>
  51 #include <linux/if_arp.h>
  52 #include <linux/if_ether.h>
  53 #include <linux/sched.h>
  54 #include <linux/delay.h>
  55 #include <linux/init.h>
  56 #include <linux/kernel.h>
  57 #include <linux/can.h>
  58 #include <linux/can/skb.h>
  59
  60 static __initconst const char banner[] =
  61         KERN_INFO "slcan: serial line CAN interface driver\n";
  62
  63 MODULE_ALIAS_LDISC(N_SLCAN);
  64 MODULE_DESCRIPTION("serial line CAN interface");
  65 MODULE_LICENSE("GPL");
  66 MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
  67
  68 #define SLCAN_MAGIC 0x53CA
  69
  70 static int maxdev = 10;         /* MAX number of SLCAN channels;
  71                                    This can be overridden with
  72                                    insmod slcan.ko maxdev=nnn   */
  73 module_param(maxdev, int, 0);
  74 MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
  75
  76 /* maximum rx buffer len: extended CAN frame with timestamp */
  77 #define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
  78
  79 struct slcan {
  80         int                     magic;
  81
  82         /* Various fields. */
  83         struct tty_struct       *tty;           /* ptr to TTY structure      */
  84         struct net_device       *dev;           /* easy for intr handling    */
  85         spinlock_t              lock;
  86
  87         /* These are pointers to the malloc()ed frame buffers. */
  88         unsigned char           rbuff[SLC_MTU]; /* receiver buffer           */
  89         int                     rcount;         /* received chars counter    */
  90         unsigned char           xbuff[SLC_MTU]; /* transmitter buffer        */
  91         unsigned char           *xhead;         /* pointer to next XMIT byte */
  92         int                     xleft;          /* bytes left in XMIT queue  */
  93
  94         unsigned long           flags;          /* Flag values/ mode etc     */
  95 #define SLF_INUSE               0               /* Channel in use            */
  96 #define SLF_ERROR               1               /* Parity, etc. error        */
  97 };
  98
  99 static struct net_device **slcan_devs;
 100
 101  /************************************************************************
 102   *                     SLCAN ENCAPSULATION FORMAT                       *
 103   ************************************************************************/
 104
 105 /*
 106  * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
 107  * frame format) a data length code (can_dlc) which can be from 0 to 8
 108  * and up to <can_dlc> data bytes as payload.
 109  * Additionally a CAN frame may become a remote transmission frame if the
 110  * RTR-bit is set. This causes another ECU to send a CAN frame with the
 111  * given can_id.
 112  *
 113  * The SLCAN ASCII representation of these different frame types is:
 114  * <type> <id> <dlc> <data>*
 115  *
 116  * Extended frames (29 bit) are defined by capital characters in the type.
 117  * RTR frames are defined as 'r' types - normal frames have 't' type:
 118  * t => 11 bit data frame
 119  * r => 11 bit RTR frame
 120  * T => 29 bit data frame
 121  * R => 29 bit RTR frame
 122  *
 123  * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
 124  * The <dlc> is a one byte ASCII number ('0' - '8')
 125  * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
 126  *
 127  * Examples:
 128  *
 129  * t1230 : can_id 0x123, can_dlc 0, no data
 130  * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
 131  * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
 132  * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
 133  *
 134  */
 135
 136  /************************************************************************
 137   *                     STANDARD SLCAN DECAPSULATION                     *
 138   ************************************************************************/
 139
 140 /* Send one completely decapsulated can_frame to the network layer */
 141 static void slc_bump(struct slcan *sl)
 142 {
 143         struct sk_buff *skb;
 144         struct can_frame cf;
 145         int i, dlc_pos, tmp;
 146         unsigned long ultmp;
 147         char cmd = sl->rbuff[0];
 148
 149         if ((cmd != 't') && (cmd != 'T') && (cmd != 'r') && (cmd != 'R'))
 150                 return;
 151
 152         if (cmd & 0x20) /* tiny chars 'r' 't' => standard frame format */
 153                 dlc_pos = 4; /* dlc position tiiid */
 154         else
 155                 dlc_pos = 9; /* dlc position Tiiiiiiiid */
 156
 157         if (!((sl->rbuff[dlc_pos] >= '0') && (sl->rbuff[dlc_pos] < '9')))
 158                 return;
 159
 160         cf.can_dlc = sl->rbuff[dlc_pos] - '0'; /* get can_dlc from ASCII val */
 161
 162         sl->rbuff[dlc_pos] = 0; /* terminate can_id string */
 163
 164         if (kstrtoul(sl->rbuff+1, 16, &ultmp))
 165                 return;
 166
 167         cf.can_id = ultmp;
 168
 169         if (!(cmd & 0x20)) /* NO tiny chars => extended frame format */
 170                 cf.can_id |= CAN_EFF_FLAG;
 171
 172         if ((cmd | 0x20) == 'r') /* RTR frame */
 173                 cf.can_id |= CAN_RTR_FLAG;
 174
 175         *(u64 *) (&cf.data) = 0; /* clear payload */
 176
 177         for (i = 0, dlc_pos++; i < cf.can_dlc; i++) {
 178                 tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
 179                 if (tmp < 0)
 180                         return;
 181                 cf.data[i] = (tmp << 4);
 182                 tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
 183                 if (tmp < 0)
 184                         return;
 185                 cf.data[i] |= tmp;
 186         }
 187
 188         skb = dev_alloc_skb(sizeof(struct can_frame) +
 189                             sizeof(struct can_skb_priv));
 190         if (!skb)
 191                 return;
 192
 193         skb->dev = sl->dev;
 194         skb->protocol = htons(ETH_P_CAN);
 195         skb->pkt_type = PACKET_BROADCAST;
 196         skb->ip_summed = CHECKSUM_UNNECESSARY;
 197
 198         can_skb_reserve(skb);
 199         can_skb_prv(skb)->ifindex = sl->dev->ifindex;
 200
 201         memcpy(skb_put(skb, sizeof(struct can_frame)),
 202                &cf, sizeof(struct can_frame));
 203         netif_rx_ni(skb);
 204
 205         sl->dev->stats.rx_packets++;
 206         sl->dev->stats.rx_bytes += cf.can_dlc;
 207 }
 208
 209 /* parse tty input stream */
 210 static void slcan_unesc(struct slcan *sl, unsigned char s)
 211 {
 212
 213         if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
 214                 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
 215                     (sl->rcount > 4))  {
 216                         slc_bump(sl);
 217                 }
 218                 sl->rcount = 0;
 219         } else {
 220                 if (!test_bit(SLF_ERROR, &sl->flags))  {
 221                         if (sl->rcount < SLC_MTU)  {
 222                                 sl->rbuff[sl->rcount++] = s;
 223                                 return;
 224                         } else {
 225                                 sl->dev->stats.rx_over_errors++;
 226                                 set_bit(SLF_ERROR, &sl->flags);
 227                         }
 228                 }
 229         }
 230 }
 231
 232  /************************************************************************
 233   *                     STANDARD SLCAN ENCAPSULATION                     *
 234   ************************************************************************/
 235
 236 /* Encapsulate one can_frame and stuff into a TTY queue. */
 237 static void slc_encaps(struct slcan *sl, struct can_frame *cf)
 238 {
 239         int actual, idx, i;
 240         char cmd;
 241
 242         if (cf->can_id & CAN_RTR_FLAG)
 243                 cmd = 'R'; /* becomes 'r' in standard frame format */
 244         else
 245                 cmd = 'T'; /* becomes 't' in standard frame format */
 246
 247         if (cf->can_id & CAN_EFF_FLAG)
 248                 sprintf(sl->xbuff, "%c%08X%d", cmd,
 249                         cf->can_id & CAN_EFF_MASK, cf->can_dlc);
 250         else
 251                 sprintf(sl->xbuff, "%c%03X%d", cmd | 0x20,
 252                         cf->can_id & CAN_SFF_MASK, cf->can_dlc);
 253
 254         idx = strlen(sl->xbuff);
 255
 256         for (i = 0; i < cf->can_dlc; i++)
 257                 sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);
 258
 259         strcat(sl->xbuff, "\r"); /* add terminating character */
 260
 261         /* Order of next two lines is *very* important.
 262          * When we are sending a little amount of data,
 263          * the transfer may be completed inside the ops->write()
 264          * routine, because it's running with interrupts enabled.
 265          * In this case we *never* got WRITE_WAKEUP event,
 266          * if we did not request it before write operation.
 267          *       14 Oct 1994  Dmitry Gorodchanin.
 268          */
 269         set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 270         actual = sl->tty->ops->write(sl->tty, sl->xbuff, strlen(sl->xbuff));
 271         sl->xleft = strlen(sl->xbuff) - actual;
 272         sl->xhead = sl->xbuff + actual;
 273         sl->dev->stats.tx_bytes += cf->can_dlc;
 274 }
 275
 276 /*
 277  * Called by the driver when there's room for more data.  If we have
 278  * more packets to send, we send them here.
 279  */
 280 static void slcan_write_wakeup(struct tty_struct *tty)
 281 {
 282         int actual;
 283         struct slcan *sl = (struct slcan *) tty->disc_data;
 284
 285         /* First make sure we're connected. */
 286         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 287                 return;
 288
 289         if (sl->xleft <= 0)  {
 290                 /* Now serial buffer is almost free & we can start
 291                  * transmission of another packet */
 292                 sl->dev->stats.tx_packets++;
 293                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 294                 netif_wake_queue(sl->dev);
 295                 return;
 296         }
 297
 298         actual = tty->ops->write(tty, sl->xhead, sl->xleft);
 299         sl->xleft -= actual;
 300         sl->xhead += actual;
 301 }
 302
 303 /* Send a can_frame to a TTY queue. */
 304 static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 305 {
 306         struct slcan *sl = netdev_priv(dev);
 307
 308         if (skb->len != sizeof(struct can_frame))
 309                 goto out;
 310
 311         spin_lock(&sl->lock);
 312         if (!netif_running(dev))  {
 313                 spin_unlock(&sl->lock);
 314                 printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
 315                 goto out;
 316         }
 317         if (sl->tty == NULL) {
 318                 spin_unlock(&sl->lock);
 319                 goto out;
 320         }
 321
 322         netif_stop_queue(sl->dev);
 323         slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
 324         spin_unlock(&sl->lock);
 325
 326 out:
 327         kfree_skb(skb);
 328         return NETDEV_TX_OK;
 329 }
 330
 331
 332 /******************************************
 333  *   Routines looking at netdevice side.
 334  ******************************************/
 335
 336 /* Netdevice UP -> DOWN routine */
 337 static int slc_close(struct net_device *dev)
 338 {
 339         struct slcan *sl = netdev_priv(dev);
 340
 341         spin_lock_bh(&sl->lock);
 342         if (sl->tty) {
 343                 /* TTY discipline is running. */
 344                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 345         }
 346         netif_stop_queue(dev);
 347         sl->rcount   = 0;
 348         sl->xleft    = 0;
 349         spin_unlock_bh(&sl->lock);
 350
 351         return 0;
 352 }
 353
 354 /* Netdevice DOWN -> UP routine */
 355 static int slc_open(struct net_device *dev)
 356 {
 357         struct slcan *sl = netdev_priv(dev);
 358
 359         if (sl->tty == NULL)
 360                 return -ENODEV;
 361
 362         sl->flags &= (1 << SLF_INUSE);
 363         netif_start_queue(dev);
 364         return 0;
 365 }
 366
 367 /* Hook the destructor so we can free slcan devs at the right point in time */
 368 static void slc_free_netdev(struct net_device *dev)
 369 {
 370         int i = dev->base_addr;
 371         free_netdev(dev);
 372         slcan_devs[i] = NULL;
 373 }
 374
 375 static const struct net_device_ops slc_netdev_ops = {
 376         .ndo_open               = slc_open,
 377         .ndo_stop               = slc_close,
 378         .ndo_start_xmit         = slc_xmit,
 379 };
 380
 381 static void slc_setup(struct net_device *dev)
 382 {
 383         dev->netdev_ops         = &slc_netdev_ops;
 384         dev->destructor         = slc_free_netdev;
 385
 386         dev->hard_header_len    = 0;
 387         dev->addr_len           = 0;
 388         dev->tx_queue_len       = 10;
 389
 390         dev->mtu                = sizeof(struct can_frame);
 391         dev->type               = ARPHRD_CAN;
 392
 393         /* New-style flags. */
 394         dev->flags              = IFF_NOARP;
 395         dev->features           = NETIF_F_HW_CSUM;
 396 }
 397
 398 /******************************************
 399   Routines looking at TTY side.
 400  ******************************************/
 401
 402 /*
 403  * Handle the 'receiver data ready' interrupt.
 404  * This function is called by the 'tty_io' module in the kernel when
 405  * a block of SLCAN data has been received, which can now be decapsulated
 406  * and sent on to some IP layer for further processing. This will not
 407  * be re-entered while running but other ldisc functions may be called
 408  * in parallel
 409  */
 410
 411 static void slcan_receive_buf(struct tty_struct *tty,
 412                               const unsigned char *cp, char *fp, int count)
 413 {
 414         struct slcan *sl = (struct slcan *) tty->disc_data;
 415
 416         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 417                 return;
 418
 419         /* Read the characters out of the buffer */
 420         while (count--) {
 421                 if (fp && *fp++) {
 422                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
 423                                 sl->dev->stats.rx_errors++;
 424                         cp++;
 425                         continue;
 426                 }
 427                 slcan_unesc(sl, *cp++);
 428         }
 429 }
 430
 431 /************************************
 432  *  slcan_open helper routines.
 433  ************************************/
 434
 435 /* Collect hanged up channels */
 436 static void slc_sync(void)
 437 {
 438         int i;
 439         struct net_device *dev;
 440         struct slcan      *sl;
 441
 442         for (i = 0; i < maxdev; i++) {
 443                 dev = slcan_devs[i];
 444                 if (dev == NULL)
 445                         break;
 446
 447                 sl = netdev_priv(dev);
 448                 if (sl->tty)
 449                         continue;
 450                 if (dev->flags & IFF_UP)
 451                         dev_close(dev);
 452         }
 453 }
 454
 455 /* Find a free SLCAN channel, and link in this `tty' line. */
 456 static struct slcan *slc_alloc(dev_t line)
 457 {
 458         int i;
 459         char name[IFNAMSIZ];
 460         struct net_device *dev = NULL;
 461         struct slcan       *sl;
 462
 463         for (i = 0; i < maxdev; i++) {
 464                 dev = slcan_devs[i];
 465                 if (dev == NULL)
 466                         break;
 467
 468         }
 469
 470         /* Sorry, too many, all slots in use */
 471         if (i >= maxdev)
 472                 return NULL;
 473
 474         sprintf(name, "slcan%d", i);
 475         dev = alloc_netdev(sizeof(*sl), name, slc_setup);
 476         if (!dev)
 477                 return NULL;
 478
 479         dev->base_addr  = i;
 480         sl = netdev_priv(dev);
 481
 482         /* Initialize channel control data */
 483         sl->magic = SLCAN_MAGIC;
 484         sl->dev = dev;
 485         spin_lock_init(&sl->lock);
 486         slcan_devs[i] = dev;
 487
 488         return sl;
 489 }
 490
 491 /*
 492  * Open the high-level part of the SLCAN channel.
 493  * This function is called by the TTY module when the
 494  * SLCAN line discipline is called for.  Because we are
 495  * sure the tty line exists, we only have to link it to
 496  * a free SLCAN channel...
 497  *
 498  * Called in process context serialized from other ldisc calls.
 499  */
 500
 501 static int slcan_open(struct tty_struct *tty)
 502 {
 503         struct slcan *sl;
 504         int err;
 505
 506         if (!capable(CAP_NET_ADMIN))
 507                 return -EPERM;
 508
 509         if (tty->ops->write == NULL)
 510                 return -EOPNOTSUPP;
 511
 512         /* RTnetlink lock is misused here to serialize concurrent
 513            opens of slcan channels. There are better ways, but it is
 514            the simplest one.
 515          */
 516         rtnl_lock();
 517
 518         /* Collect hanged up channels. */
 519         slc_sync();
 520
 521         sl = tty->disc_data;
 522
 523         err = -EEXIST;
 524         /* First make sure we're not already connected. */
 525         if (sl && sl->magic == SLCAN_MAGIC)
 526                 goto err_exit;
 527
 528         /* OK.  Find a free SLCAN channel to use. */
 529         err = -ENFILE;
 530         sl = slc_alloc(tty_devnum(tty));
 531         if (sl == NULL)
 532                 goto err_exit;
 533
 534         sl->tty = tty;
 535         tty->disc_data = sl;
 536
 537         if (!test_bit(SLF_INUSE, &sl->flags)) {
 538                 /* Perform the low-level SLCAN initialization. */
 539                 sl->rcount   = 0;
 540                 sl->xleft    = 0;
 541
 542                 set_bit(SLF_INUSE, &sl->flags);
 543
 544                 err = register_netdevice(sl->dev);
 545                 if (err)
 546                         goto err_free_chan;
 547         }
 548
 549         /* Done.  We have linked the TTY line to a channel. */
 550         rtnl_unlock();
 551         tty->receive_room = 65536;      /* We don't flow control */
 552
 553         /* TTY layer expects 0 on success */
 554         return 0;
 555
 556 err_free_chan:
 557         sl->tty = NULL;
 558         tty->disc_data = NULL;
 559         clear_bit(SLF_INUSE, &sl->flags);
 560
 561 err_exit:
 562         rtnl_unlock();
 563
 564         /* Count references from TTY module */
 565         return err;
 566 }
 567
 568 /*
 569  * Close down a SLCAN channel.
 570  * This means flushing out any pending queues, and then returning. This
 571  * call is serialized against other ldisc functions.
 572  *
 573  * We also use this method for a hangup event.
 574  */
 575
 576 static void slcan_close(struct tty_struct *tty)
 577 {
 578         struct slcan *sl = (struct slcan *) tty->disc_data;
 579
 580         /* First make sure we're connected. */
 581         if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
 582                 return;
 583
 584         tty->disc_data = NULL;
 585         sl->tty = NULL;
 586
 587         /* Flush network side */
 588         unregister_netdev(sl->dev);
 589         /* This will complete via sl_free_netdev */
 590 }
 591
 592 static int slcan_hangup(struct tty_struct *tty)
 593 {
 594         slcan_close(tty);
 595         return 0;
 596 }
 597
 598 /* Perform I/O control on an active SLCAN channel. */
 599 static int slcan_ioctl(struct tty_struct *tty, struct file *file,
 600                        unsigned int cmd, unsigned long arg)
 601 {
 602         struct slcan *sl = (struct slcan *) tty->disc_data;
 603         unsigned int tmp;
 604
 605         /* First make sure we're connected. */
 606         if (!sl || sl->magic != SLCAN_MAGIC)
 607                 return -EINVAL;
 608
 609         switch (cmd) {
 610         case SIOCGIFNAME:
 611                 tmp = strlen(sl->dev->name) + 1;
 612                 if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
 613                         return -EFAULT;
 614                 return 0;
 615
 616         case SIOCSIFHWADDR:
 617                 return -EINVAL;
 618
 619         default:
 620                 return tty_mode_ioctl(tty, file, cmd, arg);
 621         }
 622 }
 623
 624 static struct tty_ldisc_ops slc_ldisc = {
 625         .owner          = THIS_MODULE,
 626         .magic          = TTY_LDISC_MAGIC,
 627         .name           = "slcan",
 628         .open           = slcan_open,
 629         .close          = slcan_close,
 630         .hangup         = slcan_hangup,
 631         .ioctl          = slcan_ioctl,
 632         .receive_buf    = slcan_receive_buf,
 633         .write_wakeup   = slcan_write_wakeup,
 634 };
 635
 636 static int __init slcan_init(void)
 637 {
 638         int status;
 639
 640         if (maxdev < 4)
 641                 maxdev = 4; /* Sanity */
 642
 643         printk(banner);
 644         printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
 645
 646         slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
 647         if (!slcan_devs)
 648                 return -ENOMEM;
 649
 650         /* Fill in our line protocol discipline, and register it */
 651         status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
 652         if (status)  {
 653                 printk(KERN_ERR "slcan: can't register line discipline\n");
 654                 kfree(slcan_devs);
 655         }
 656         return status;
 657 }
 658
 659 static void __exit slcan_exit(void)
 660 {
 661         int i;
 662         struct net_device *dev;
 663         struct slcan *sl;
 664         unsigned long timeout = jiffies + HZ;
 665         int busy = 0;
 666
 667         if (slcan_devs == NULL)
 668                 return;
 669
 670         /* First of all: check for active disciplines and hangup them.
 671          */
 672         do {
 673                 if (busy)
 674                         msleep_interruptible(100);
 675
 676                 busy = 0;
 677                 for (i = 0; i < maxdev; i++) {
 678                         dev = slcan_devs[i];
 679                         if (!dev)
 680                                 continue;
 681                         sl = netdev_priv(dev);
 682                         spin_lock_bh(&sl->lock);
 683                         if (sl->tty) {
 684                                 busy++;
 685                                 tty_hangup(sl->tty);
 686                         }
 687                         spin_unlock_bh(&sl->lock);
 688                 }
 689         } while (busy && time_before(jiffies, timeout));
 690
 691         /* FIXME: hangup is async so we should wait when doing this second
 692            phase */
 693
 694         for (i = 0; i < maxdev; i++) {
 695                 dev = slcan_devs[i];
 696                 if (!dev)
 697                         continue;
 698                 slcan_devs[i] = NULL;
 699
 700                 sl = netdev_priv(dev);
 701                 if (sl->tty) {
 702                         printk(KERN_ERR "%s: tty discipline still running\n",
 703                                dev->name);
 704                         /* Intentionally leak the control block. */
 705                         dev->destructor = NULL;
 706                 }
 707
 708                 unregister_netdev(dev);
 709         }
 710
 711         kfree(slcan_devs);
 712         slcan_devs = NULL;
 713
 714         i = tty_unregister_ldisc(N_SLCAN);
 715         if (i)
 716                 printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
 717 }
 718
 719 module_init(slcan_init);
 720 module_exit(slcan_exit);