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 #define SLC_CMD_LEN 1
  80 #define SLC_SFF_ID_LEN 3
  81 #define SLC_EFF_ID_LEN 8
  82
  83 struct slcan {
  84         int                     magic;
  85
  86         /* Various fields. */
  87         struct tty_struct       *tty;           /* ptr to TTY structure      */
  88         struct net_device       *dev;           /* easy for intr handling    */
  89         spinlock_t              lock;
  90
  91         /* These are pointers to the malloc()ed frame buffers. */
  92         unsigned char           rbuff[SLC_MTU]; /* receiver buffer           */
  93         int                     rcount;         /* received chars counter    */
  94         unsigned char           xbuff[SLC_MTU]; /* transmitter buffer        */
  95         unsigned char           *xhead;         /* pointer to next XMIT byte */
  96         int                     xleft;          /* bytes left in XMIT queue  */
  97
  98         unsigned long           flags;          /* Flag values/ mode etc     */
  99 #define SLF_INUSE               0               /* Channel in use            */
 100 #define SLF_ERROR               1               /* Parity, etc. error        */
 101 };
 102
 103 static struct net_device **slcan_devs;
 104
 105  /************************************************************************
 106   *                     SLCAN ENCAPSULATION FORMAT                       *
 107   ************************************************************************/
 108
 109 /*
 110  * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
 111  * frame format) a data length code (can_dlc) which can be from 0 to 8
 112  * and up to <can_dlc> data bytes as payload.
 113  * Additionally a CAN frame may become a remote transmission frame if the
 114  * RTR-bit is set. This causes another ECU to send a CAN frame with the
 115  * given can_id.
 116  *
 117  * The SLCAN ASCII representation of these different frame types is:
 118  * <type> <id> <dlc> <data>*
 119  *
 120  * Extended frames (29 bit) are defined by capital characters in the type.
 121  * RTR frames are defined as 'r' types - normal frames have 't' type:
 122  * t => 11 bit data frame
 123  * r => 11 bit RTR frame
 124  * T => 29 bit data frame
 125  * R => 29 bit RTR frame
 126  *
 127  * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
 128  * The <dlc> is a one byte ASCII number ('0' - '8')
 129  * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
 130  *
 131  * Examples:
 132  *
 133  * t1230 : can_id 0x123, can_dlc 0, no data
 134  * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
 135  * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
 136  * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
 137  *
 138  */
 139
 140  /************************************************************************
 141   *                     STANDARD SLCAN DECAPSULATION                     *
 142   ************************************************************************/
 143
 144 /* Send one completely decapsulated can_frame to the network layer */
 145 static void slc_bump(struct slcan *sl)
 146 {
 147         struct sk_buff *skb;
 148         struct can_frame cf;
 149         int i, tmp;
 150         u32 tmpid;
 151         char *cmd = sl->rbuff;
 152
 153         cf.can_id = 0;
 154
 155         switch (*cmd) {
 156         case 'r':
 157                 cf.can_id = CAN_RTR_FLAG;
 158                 /* fallthrough */
 159         case 't':
 160                 /* store dlc ASCII value and terminate SFF CAN ID string */
 161                 cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
 162                 sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN] = 0;
 163                 /* point to payload data behind the dlc */
 164                 cmd += SLC_CMD_LEN + SLC_SFF_ID_LEN + 1;
 165                 break;
 166         case 'R':
 167                 cf.can_id = CAN_RTR_FLAG;
 168                 /* fallthrough */
 169         case 'T':
 170                 cf.can_id |= CAN_EFF_FLAG;
 171                 /* store dlc ASCII value and terminate EFF CAN ID string */
 172                 cf.can_dlc = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
 173                 sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN] = 0;
 174                 /* point to payload data behind the dlc */
 175                 cmd += SLC_CMD_LEN + SLC_EFF_ID_LEN + 1;
 176                 break;
 177         default:
 178                 return;
 179         }
 180
 181         if (kstrtou32(sl->rbuff + SLC_CMD_LEN, 16, &tmpid))
 182                 return;
 183
 184         cf.can_id |= tmpid;
 185
 186         /* get can_dlc from sanitized ASCII value */
 187         if (cf.can_dlc >= '0' && cf.can_dlc < '9')
 188                 cf.can_dlc -= '0';
 189         else
 190                 return;
 191
 192         *(u64 *) (&cf.data) = 0; /* clear payload */
 193
 194         /* RTR frames may have a dlc > 0 but they never have any data bytes */
 195         if (!(cf.can_id & CAN_RTR_FLAG)) {
 196                 for (i = 0; i < cf.can_dlc; i++) {
 197                         tmp = hex_to_bin(*cmd++);
 198                         if (tmp < 0)
 199                                 return;
 200                         cf.data[i] = (tmp << 4);
 201                         tmp = hex_to_bin(*cmd++);
 202                         if (tmp < 0)
 203                                 return;
 204                         cf.data[i] |= tmp;
 205                 }
 206         }
 207
 208         skb = dev_alloc_skb(sizeof(struct can_frame) +
 209                             sizeof(struct can_skb_priv));
 210         if (!skb)
 211                 return;
 212
 213         skb->dev = sl->dev;
 214         skb->protocol = htons(ETH_P_CAN);
 215         skb->pkt_type = PACKET_BROADCAST;
 216         skb->ip_summed = CHECKSUM_UNNECESSARY;
 217
 218         can_skb_reserve(skb);
 219         can_skb_prv(skb)->ifindex = sl->dev->ifindex;
 220
 221         memcpy(skb_put(skb, sizeof(struct can_frame)),
 222                &cf, sizeof(struct can_frame));
 223         netif_rx_ni(skb);
 224
 225         sl->dev->stats.rx_packets++;
 226         sl->dev->stats.rx_bytes += cf.can_dlc;
 227 }
 228
 229 /* parse tty input stream */
 230 static void slcan_unesc(struct slcan *sl, unsigned char s)
 231 {
 232         if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
 233                 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
 234                     (sl->rcount > 4))  {
 235                         slc_bump(sl);
 236                 }
 237                 sl->rcount = 0;
 238         } else {
 239                 if (!test_bit(SLF_ERROR, &sl->flags))  {
 240                         if (sl->rcount < SLC_MTU)  {
 241                                 sl->rbuff[sl->rcount++] = s;
 242                                 return;
 243                         } else {
 244                                 sl->dev->stats.rx_over_errors++;
 245                                 set_bit(SLF_ERROR, &sl->flags);
 246                         }
 247                 }
 248         }
 249 }
 250
 251  /************************************************************************
 252   *                     STANDARD SLCAN ENCAPSULATION                     *
 253   ************************************************************************/
 254
 255 /* Encapsulate one can_frame and stuff into a TTY queue. */
 256 static void slc_encaps(struct slcan *sl, struct can_frame *cf)
 257 {
 258         int actual, i;
 259         unsigned char *pos;
 260         unsigned char *endpos;
 261         canid_t id = cf->can_id;
 262
 263         pos = sl->xbuff;
 264
 265         if (cf->can_id & CAN_RTR_FLAG)
 266                 *pos = 'R'; /* becomes 'r' in standard frame format (SFF) */
 267         else
 268                 *pos = 'T'; /* becomes 't' in standard frame format (SSF) */
 269
 270         /* determine number of chars for the CAN-identifier */
 271         if (cf->can_id & CAN_EFF_FLAG) {
 272                 id &= CAN_EFF_MASK;
 273                 endpos = pos + SLC_EFF_ID_LEN;
 274         } else {
 275                 *pos |= 0x20; /* convert R/T to lower case for SFF */
 276                 id &= CAN_SFF_MASK;
 277                 endpos = pos + SLC_SFF_ID_LEN;
 278         }
 279
 280         /* build 3 (SFF) or 8 (EFF) digit CAN identifier */
 281         pos++;
 282         while (endpos >= pos) {
 283                 *endpos-- = hex_asc_upper[id & 0xf];
 284                 id >>= 4;
 285         }
 286
 287         pos += (cf->can_id & CAN_EFF_FLAG) ? SLC_EFF_ID_LEN : SLC_SFF_ID_LEN;
 288
 289         *pos++ = cf->can_dlc + '0';
 290
 291         /* RTR frames may have a dlc > 0 but they never have any data bytes */
 292         if (!(cf->can_id & CAN_RTR_FLAG)) {
 293                 for (i = 0; i < cf->can_dlc; i++)
 294                         pos = hex_byte_pack_upper(pos, cf->data[i]);
 295         }
 296
 297         *pos++ = '\r';
 298
 299         /* Order of next two lines is *very* important.
 300          * When we are sending a little amount of data,
 301          * the transfer may be completed inside the ops->write()
 302          * routine, because it's running with interrupts enabled.
 303          * In this case we *never* got WRITE_WAKEUP event,
 304          * if we did not request it before write operation.
 305          *       14 Oct 1994  Dmitry Gorodchanin.
 306          */
 307         set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 308         actual = sl->tty->ops->write(sl->tty, sl->xbuff, pos - sl->xbuff);
 309         sl->xleft = (pos - sl->xbuff) - actual;
 310         sl->xhead = sl->xbuff + actual;
 311         sl->dev->stats.tx_bytes += cf->can_dlc;
 312 }
 313
 314 /*
 315  * Called by the driver when there's room for more data.  If we have
 316  * more packets to send, we send them here.
 317  */
 318 static void slcan_write_wakeup(struct tty_struct *tty)
 319 {
 320         int actual;
 321         struct slcan *sl = (struct slcan *) tty->disc_data;
 322
 323         /* First make sure we're connected. */
 324         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 325                 return;
 326
 327         spin_lock(&sl->lock);
 328         if (sl->xleft <= 0)  {
 329                 /* Now serial buffer is almost free & we can start
 330                  * transmission of another packet */
 331                 sl->dev->stats.tx_packets++;
 332                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 333                 spin_unlock(&sl->lock);
 334                 netif_wake_queue(sl->dev);
 335                 return;
 336         }
 337
 338         actual = tty->ops->write(tty, sl->xhead, sl->xleft);
 339         sl->xleft -= actual;
 340         sl->xhead += actual;
 341         spin_unlock(&sl->lock);
 342 }
 343
 344 /* Send a can_frame to a TTY queue. */
 345 static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 346 {
 347         struct slcan *sl = netdev_priv(dev);
 348
 349         if (skb->len != sizeof(struct can_frame))
 350                 goto out;
 351
 352         spin_lock(&sl->lock);
 353         if (!netif_running(dev))  {
 354                 spin_unlock(&sl->lock);
 355                 printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
 356                 goto out;
 357         }
 358         if (sl->tty == NULL) {
 359                 spin_unlock(&sl->lock);
 360                 goto out;
 361         }
 362
 363         netif_stop_queue(sl->dev);
 364         slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
 365         spin_unlock(&sl->lock);
 366
 367 out:
 368         kfree_skb(skb);
 369         return NETDEV_TX_OK;
 370 }
 371
 372
 373 /******************************************
 374  *   Routines looking at netdevice side.
 375  ******************************************/
 376
 377 /* Netdevice UP -> DOWN routine */
 378 static int slc_close(struct net_device *dev)
 379 {
 380         struct slcan *sl = netdev_priv(dev);
 381
 382         spin_lock_bh(&sl->lock);
 383         if (sl->tty) {
 384                 /* TTY discipline is running. */
 385                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 386         }
 387         netif_stop_queue(dev);
 388         sl->rcount   = 0;
 389         sl->xleft    = 0;
 390         spin_unlock_bh(&sl->lock);
 391
 392         return 0;
 393 }
 394
 395 /* Netdevice DOWN -> UP routine */
 396 static int slc_open(struct net_device *dev)
 397 {
 398         struct slcan *sl = netdev_priv(dev);
 399
 400         if (sl->tty == NULL)
 401                 return -ENODEV;
 402
 403         sl->flags &= (1 << SLF_INUSE);
 404         netif_start_queue(dev);
 405         return 0;
 406 }
 407
 408 /* Hook the destructor so we can free slcan devs at the right point in time */
 409 static void slc_free_netdev(struct net_device *dev)
 410 {
 411         int i = dev->base_addr;
 412         free_netdev(dev);
 413         slcan_devs[i] = NULL;
 414 }
 415
 416 static const struct net_device_ops slc_netdev_ops = {
 417         .ndo_open               = slc_open,
 418         .ndo_stop               = slc_close,
 419         .ndo_start_xmit         = slc_xmit,
 420 };
 421
 422 static void slc_setup(struct net_device *dev)
 423 {
 424         dev->netdev_ops         = &slc_netdev_ops;
 425         dev->destructor         = slc_free_netdev;
 426
 427         dev->hard_header_len    = 0;
 428         dev->addr_len           = 0;
 429         dev->tx_queue_len       = 10;
 430
 431         dev->mtu                = sizeof(struct can_frame);
 432         dev->type               = ARPHRD_CAN;
 433
 434         /* New-style flags. */
 435         dev->flags              = IFF_NOARP;
 436         dev->features           = NETIF_F_HW_CSUM;
 437 }
 438
 439 /******************************************
 440   Routines looking at TTY side.
 441  ******************************************/
 442
 443 /*
 444  * Handle the 'receiver data ready' interrupt.
 445  * This function is called by the 'tty_io' module in the kernel when
 446  * a block of SLCAN data has been received, which can now be decapsulated
 447  * and sent on to some IP layer for further processing. This will not
 448  * be re-entered while running but other ldisc functions may be called
 449  * in parallel
 450  */
 451
 452 static void slcan_receive_buf(struct tty_struct *tty,
 453                               const unsigned char *cp, char *fp, int count)
 454 {
 455         struct slcan *sl = (struct slcan *) tty->disc_data;
 456
 457         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 458                 return;
 459
 460         /* Read the characters out of the buffer */
 461         while (count--) {
 462                 if (fp && *fp++) {
 463                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
 464                                 sl->dev->stats.rx_errors++;
 465                         cp++;
 466                         continue;
 467                 }
 468                 slcan_unesc(sl, *cp++);
 469         }
 470 }
 471
 472 /************************************
 473  *  slcan_open helper routines.
 474  ************************************/
 475
 476 /* Collect hanged up channels */
 477 static void slc_sync(void)
 478 {
 479         int i;
 480         struct net_device *dev;
 481         struct slcan      *sl;
 482
 483         for (i = 0; i < maxdev; i++) {
 484                 dev = slcan_devs[i];
 485                 if (dev == NULL)
 486                         break;
 487
 488                 sl = netdev_priv(dev);
 489                 if (sl->tty)
 490                         continue;
 491                 if (dev->flags & IFF_UP)
 492                         dev_close(dev);
 493         }
 494 }
 495
 496 /* Find a free SLCAN channel, and link in this `tty' line. */
 497 static struct slcan *slc_alloc(dev_t line)
 498 {
 499         int i;
 500         char name[IFNAMSIZ];
 501         struct net_device *dev = NULL;
 502         struct slcan       *sl;
 503
 504         for (i = 0; i < maxdev; i++) {
 505                 dev = slcan_devs[i];
 506                 if (dev == NULL)
 507                         break;
 508
 509         }
 510
 511         /* Sorry, too many, all slots in use */
 512         if (i >= maxdev)
 513                 return NULL;
 514
 515         sprintf(name, "slcan%d", i);
 516         dev = alloc_netdev(sizeof(*sl), name, slc_setup);
 517         if (!dev)
 518                 return NULL;
 519
 520         dev->base_addr  = i;
 521         sl = netdev_priv(dev);
 522
 523         /* Initialize channel control data */
 524         sl->magic = SLCAN_MAGIC;
 525         sl->dev = dev;
 526         spin_lock_init(&sl->lock);
 527         slcan_devs[i] = dev;
 528
 529         return sl;
 530 }
 531
 532 /*
 533  * Open the high-level part of the SLCAN channel.
 534  * This function is called by the TTY module when the
 535  * SLCAN line discipline is called for.  Because we are
 536  * sure the tty line exists, we only have to link it to
 537  * a free SLCAN channel...
 538  *
 539  * Called in process context serialized from other ldisc calls.
 540  */
 541
 542 static int slcan_open(struct tty_struct *tty)
 543 {
 544         struct slcan *sl;
 545         int err;
 546
 547         if (!capable(CAP_NET_ADMIN))
 548                 return -EPERM;
 549
 550         if (tty->ops->write == NULL)
 551                 return -EOPNOTSUPP;
 552
 553         /* RTnetlink lock is misused here to serialize concurrent
 554            opens of slcan channels. There are better ways, but it is
 555            the simplest one.
 556          */
 557         rtnl_lock();
 558
 559         /* Collect hanged up channels. */
 560         slc_sync();
 561
 562         sl = tty->disc_data;
 563
 564         err = -EEXIST;
 565         /* First make sure we're not already connected. */
 566         if (sl && sl->magic == SLCAN_MAGIC)
 567                 goto err_exit;
 568
 569         /* OK.  Find a free SLCAN channel to use. */
 570         err = -ENFILE;
 571         sl = slc_alloc(tty_devnum(tty));
 572         if (sl == NULL)
 573                 goto err_exit;
 574
 575         sl->tty = tty;
 576         tty->disc_data = sl;
 577
 578         if (!test_bit(SLF_INUSE, &sl->flags)) {
 579                 /* Perform the low-level SLCAN initialization. */
 580                 sl->rcount   = 0;
 581                 sl->xleft    = 0;
 582
 583                 set_bit(SLF_INUSE, &sl->flags);
 584
 585                 err = register_netdevice(sl->dev);
 586                 if (err)
 587                         goto err_free_chan;
 588         }
 589
 590         /* Done.  We have linked the TTY line to a channel. */
 591         rtnl_unlock();
 592         tty->receive_room = 65536;      /* We don't flow control */
 593
 594         /* TTY layer expects 0 on success */
 595         return 0;
 596
 597 err_free_chan:
 598         sl->tty = NULL;
 599         tty->disc_data = NULL;
 600         clear_bit(SLF_INUSE, &sl->flags);
 601
 602 err_exit:
 603         rtnl_unlock();
 604
 605         /* Count references from TTY module */
 606         return err;
 607 }
 608
 609 /*
 610  * Close down a SLCAN channel.
 611  * This means flushing out any pending queues, and then returning. This
 612  * call is serialized against other ldisc functions.
 613  *
 614  * We also use this method for a hangup event.
 615  */
 616
 617 static void slcan_close(struct tty_struct *tty)
 618 {
 619         struct slcan *sl = (struct slcan *) tty->disc_data;
 620
 621         /* First make sure we're connected. */
 622         if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
 623                 return;
 624
 625         tty->disc_data = NULL;
 626         sl->tty = NULL;
 627
 628         /* Flush network side */
 629         unregister_netdev(sl->dev);
 630         /* This will complete via sl_free_netdev */
 631 }
 632
 633 static int slcan_hangup(struct tty_struct *tty)
 634 {
 635         slcan_close(tty);
 636         return 0;
 637 }
 638
 639 /* Perform I/O control on an active SLCAN channel. */
 640 static int slcan_ioctl(struct tty_struct *tty, struct file *file,
 641                        unsigned int cmd, unsigned long arg)
 642 {
 643         struct slcan *sl = (struct slcan *) tty->disc_data;
 644         unsigned int tmp;
 645
 646         /* First make sure we're connected. */
 647         if (!sl || sl->magic != SLCAN_MAGIC)
 648                 return -EINVAL;
 649
 650         switch (cmd) {
 651         case SIOCGIFNAME:
 652                 tmp = strlen(sl->dev->name) + 1;
 653                 if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
 654                         return -EFAULT;
 655                 return 0;
 656
 657         case SIOCSIFHWADDR:
 658                 return -EINVAL;
 659
 660         default:
 661                 return tty_mode_ioctl(tty, file, cmd, arg);
 662         }
 663 }
 664
 665 static struct tty_ldisc_ops slc_ldisc = {
 666         .owner          = THIS_MODULE,
 667         .magic          = TTY_LDISC_MAGIC,
 668         .name           = "slcan",
 669         .open           = slcan_open,
 670         .close          = slcan_close,
 671         .hangup         = slcan_hangup,
 672         .ioctl          = slcan_ioctl,
 673         .receive_buf    = slcan_receive_buf,
 674         .write_wakeup   = slcan_write_wakeup,
 675 };
 676
 677 static int __init slcan_init(void)
 678 {
 679         int status;
 680
 681         if (maxdev < 4)
 682                 maxdev = 4; /* Sanity */
 683
 684         printk(banner);
 685         printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
 686
 687         slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
 688         if (!slcan_devs)
 689                 return -ENOMEM;
 690
 691         /* Fill in our line protocol discipline, and register it */
 692         status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
 693         if (status)  {
 694                 printk(KERN_ERR "slcan: can't register line discipline\n");
 695                 kfree(slcan_devs);
 696         }
 697         return status;
 698 }
 699
 700 static void __exit slcan_exit(void)
 701 {
 702         int i;
 703         struct net_device *dev;
 704         struct slcan *sl;
 705         unsigned long timeout = jiffies + HZ;
 706         int busy = 0;
 707
 708         if (slcan_devs == NULL)
 709                 return;
 710
 711         /* First of all: check for active disciplines and hangup them.
 712          */
 713         do {
 714                 if (busy)
 715                         msleep_interruptible(100);
 716
 717                 busy = 0;
 718                 for (i = 0; i < maxdev; i++) {
 719                         dev = slcan_devs[i];
 720                         if (!dev)
 721                                 continue;
 722                         sl = netdev_priv(dev);
 723                         spin_lock_bh(&sl->lock);
 724                         if (sl->tty) {
 725                                 busy++;
 726                                 tty_hangup(sl->tty);
 727                         }
 728                         spin_unlock_bh(&sl->lock);
 729                 }
 730         } while (busy && time_before(jiffies, timeout));
 731
 732         /* FIXME: hangup is async so we should wait when doing this second
 733            phase */
 734
 735         for (i = 0; i < maxdev; i++) {
 736                 dev = slcan_devs[i];
 737                 if (!dev)
 738                         continue;
 739                 slcan_devs[i] = NULL;
 740
 741                 sl = netdev_priv(dev);
 742                 if (sl->tty) {
 743                         printk(KERN_ERR "%s: tty discipline still running\n",
 744                                dev->name);
 745                         /* Intentionally leak the control block. */
 746                         dev->destructor = NULL;
 747                 }
 748
 749                 unregister_netdev(dev);
 750         }
 751
 752         kfree(slcan_devs);
 753         slcan_devs = NULL;
 754
 755         i = tty_unregister_ldisc(N_SLCAN);
 756         if (i)
 757                 printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
 758 }
 759
 760 module_init(slcan_init);
 761 module_exit(slcan_exit);