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