drivers/net/can/slcan.c

   1 /*
   2  * slcan.c - serial line CAN interface driver (using tty line discipline)
   3  *
   4  * This file is derived from linux/drivers/net/slip/slip.c
   5  *
   6  * slip.c Authors  : Laurence Culhane <loz@holmes.demon.co.uk>
   7  *                   Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
   8  * slcan.c Author  : Oliver Hartkopp <socketcan@hartkopp.net>
   9  *
  10  * This program is free software; you can redistribute it and/or modify it
  11  * under the terms of the GNU General Public License as published by the
  12  * Free Software Foundation; either version 2 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License along
  21  * with this program; if not, see http://www.gnu.org/licenses/gpl.html
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  24  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  25  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  26  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  27  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  28  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  29  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  30  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  31  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  32  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  33  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  34  * DAMAGE.
  35  *
  36  */
  37
  38 #include <linux/module.h>
  39 #include <linux/moduleparam.h>
  40
  41 #include <linux/uaccess.h>
  42 #include <linux/bitops.h>
  43 #include <linux/string.h>
  44 #include <linux/tty.h>
  45 #include <linux/errno.h>
  46 #include <linux/netdevice.h>
  47 #include <linux/skbuff.h>
  48 #include <linux/rtnetlink.h>
  49 #include <linux/if_arp.h>
  50 #include <linux/if_ether.h>
  51 #include <linux/sched.h>
  52 #include <linux/delay.h>
  53 #include <linux/init.h>
  54 #include <linux/kernel.h>
  55 #include <linux/workqueue.h>
  56 #include <linux/can.h>
  57 #include <linux/can/skb.h>
  58
  59 static __initconst 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 #define SLC_CMD_LEN 1
  79 #define SLC_SFF_ID_LEN 3
  80 #define SLC_EFF_ID_LEN 8
  81
  82 struct slcan {
  83         int                     magic;
  84
  85         /* Various fields. */
  86         struct tty_struct       *tty;           /* ptr to TTY structure      */
  87         struct net_device       *dev;           /* easy for intr handling    */
  88         spinlock_t              lock;
  89         struct work_struct      tx_work;        /* Flushes transmit buffer   */
  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         memset(&cf, 0, sizeof(cf));
 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         /* RTR frames may have a dlc > 0 but they never have any data bytes */
 193         if (!(cf.can_id & CAN_RTR_FLAG)) {
 194                 for (i = 0; i < cf.can_dlc; i++) {
 195                         tmp = hex_to_bin(*cmd++);
 196                         if (tmp < 0)
 197                                 return;
 198                         cf.data[i] = (tmp << 4);
 199                         tmp = hex_to_bin(*cmd++);
 200                         if (tmp < 0)
 201                                 return;
 202                         cf.data[i] |= tmp;
 203                 }
 204         }
 205
 206         skb = dev_alloc_skb(sizeof(struct can_frame) +
 207                             sizeof(struct can_skb_priv));
 208         if (!skb)
 209                 return;
 210
 211         skb->dev = sl->dev;
 212         skb->protocol = htons(ETH_P_CAN);
 213         skb->pkt_type = PACKET_BROADCAST;
 214         skb->ip_summed = CHECKSUM_UNNECESSARY;
 215
 216         can_skb_reserve(skb);
 217         can_skb_prv(skb)->ifindex = sl->dev->ifindex;
 218
 219         memcpy(skb_put(skb, sizeof(struct can_frame)),
 220                &cf, sizeof(struct can_frame));
 221         netif_rx_ni(skb);
 222
 223         sl->dev->stats.rx_packets++;
 224         sl->dev->stats.rx_bytes += cf.can_dlc;
 225 }
 226
 227 /* parse tty input stream */
 228 static void slcan_unesc(struct slcan *sl, unsigned char s)
 229 {
 230         if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
 231                 if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
 232                     (sl->rcount > 4))  {
 233                         slc_bump(sl);
 234                 }
 235                 sl->rcount = 0;
 236         } else {
 237                 if (!test_bit(SLF_ERROR, &sl->flags))  {
 238                         if (sl->rcount < SLC_MTU)  {
 239                                 sl->rbuff[sl->rcount++] = s;
 240                                 return;
 241                         } else {
 242                                 sl->dev->stats.rx_over_errors++;
 243                                 set_bit(SLF_ERROR, &sl->flags);
 244                         }
 245                 }
 246         }
 247 }
 248
 249  /************************************************************************
 250   *                     STANDARD SLCAN ENCAPSULATION                     *
 251   ************************************************************************/
 252
 253 /* Encapsulate one can_frame and stuff into a TTY queue. */
 254 static void slc_encaps(struct slcan *sl, struct can_frame *cf)
 255 {
 256         int actual, i;
 257         unsigned char *pos;
 258         unsigned char *endpos;
 259         canid_t id = cf->can_id;
 260
 261         pos = sl->xbuff;
 262
 263         if (cf->can_id & CAN_RTR_FLAG)
 264                 *pos = 'R'; /* becomes 'r' in standard frame format (SFF) */
 265         else
 266                 *pos = 'T'; /* becomes 't' in standard frame format (SSF) */
 267
 268         /* determine number of chars for the CAN-identifier */
 269         if (cf->can_id & CAN_EFF_FLAG) {
 270                 id &= CAN_EFF_MASK;
 271                 endpos = pos + SLC_EFF_ID_LEN;
 272         } else {
 273                 *pos |= 0x20; /* convert R/T to lower case for SFF */
 274                 id &= CAN_SFF_MASK;
 275                 endpos = pos + SLC_SFF_ID_LEN;
 276         }
 277
 278         /* build 3 (SFF) or 8 (EFF) digit CAN identifier */
 279         pos++;
 280         while (endpos >= pos) {
 281                 *endpos-- = hex_asc_upper[id & 0xf];
 282                 id >>= 4;
 283         }
 284
 285         pos += (cf->can_id & CAN_EFF_FLAG) ? SLC_EFF_ID_LEN : SLC_SFF_ID_LEN;
 286
 287         *pos++ = cf->can_dlc + '0';
 288
 289         /* RTR frames may have a dlc > 0 but they never have any data bytes */
 290         if (!(cf->can_id & CAN_RTR_FLAG)) {
 291                 for (i = 0; i < cf->can_dlc; i++)
 292                         pos = hex_byte_pack_upper(pos, cf->data[i]);
 293         }
 294
 295         *pos++ = '\r';
 296
 297         /* Order of next two lines is *very* important.
 298          * When we are sending a little amount of data,
 299          * the transfer may be completed inside the ops->write()
 300          * routine, because it's running with interrupts enabled.
 301          * In this case we *never* got WRITE_WAKEUP event,
 302          * if we did not request it before write operation.
 303          *       14 Oct 1994  Dmitry Gorodchanin.
 304          */
 305         set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 306         actual = sl->tty->ops->write(sl->tty, sl->xbuff, pos - sl->xbuff);
 307         sl->xleft = (pos - sl->xbuff) - actual;
 308         sl->xhead = sl->xbuff + actual;
 309         sl->dev->stats.tx_bytes += cf->can_dlc;
 310 }
 311
 312 /* Write out any remaining transmit buffer. Scheduled when tty is writable */
 313 static void slcan_transmit(struct work_struct *work)
 314 {
 315         struct slcan *sl = container_of(work, struct slcan, tx_work);
 316         int actual;
 317
 318         spin_lock_bh(&sl->lock);
 319         /* First make sure we're connected. */
 320         if (!sl->tty || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev)) {
 321                 spin_unlock_bh(&sl->lock);
 322                 return;
 323         }
 324
 325         if (sl->xleft <= 0)  {
 326                 /* Now serial buffer is almost free & we can start
 327                  * transmission of another packet */
 328                 sl->dev->stats.tx_packets++;
 329                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 330                 spin_unlock_bh(&sl->lock);
 331                 netif_wake_queue(sl->dev);
 332                 return;
 333         }
 334
 335         actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft);
 336         sl->xleft -= actual;
 337         sl->xhead += actual;
 338         spin_unlock_bh(&sl->lock);
 339 }
 340
 341 /*
 342  * Called by the driver when there's room for more data.
 343  * Schedule the transmit.
 344  */
 345 static void slcan_write_wakeup(struct tty_struct *tty)
 346 {
 347         struct slcan *sl;
 348
 349         rcu_read_lock();
 350         sl = rcu_dereference(tty->disc_data);
 351         if (!sl)
 352                 goto out;
 353
 354         schedule_work(&sl->tx_work);
 355 out:
 356         rcu_read_unlock();
 357 }
 358
 359 /* Send a can_frame to a TTY queue. */
 360 static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 361 {
 362         struct slcan *sl = netdev_priv(dev);
 363
 364         if (skb->len != sizeof(struct can_frame))
 365                 goto out;
 366
 367         spin_lock(&sl->lock);
 368         if (!netif_running(dev))  {
 369                 spin_unlock(&sl->lock);
 370                 printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
 371                 goto out;
 372         }
 373         if (sl->tty == NULL) {
 374                 spin_unlock(&sl->lock);
 375                 goto out;
 376         }
 377
 378         netif_stop_queue(sl->dev);
 379         slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
 380         spin_unlock(&sl->lock);
 381
 382 out:
 383         kfree_skb(skb);
 384         return NETDEV_TX_OK;
 385 }
 386
 387
 388 /******************************************
 389  *   Routines looking at netdevice side.
 390  ******************************************/
 391
 392 /* Netdevice UP -> DOWN routine */
 393 static int slc_close(struct net_device *dev)
 394 {
 395         struct slcan *sl = netdev_priv(dev);
 396
 397         spin_lock_bh(&sl->lock);
 398         if (sl->tty) {
 399                 /* TTY discipline is running. */
 400                 clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 401         }
 402         netif_stop_queue(dev);
 403         sl->rcount   = 0;
 404         sl->xleft    = 0;
 405         spin_unlock_bh(&sl->lock);
 406
 407         return 0;
 408 }
 409
 410 /* Netdevice DOWN -> UP routine */
 411 static int slc_open(struct net_device *dev)
 412 {
 413         struct slcan *sl = netdev_priv(dev);
 414
 415         if (sl->tty == NULL)
 416                 return -ENODEV;
 417
 418         sl->flags &= (1 << SLF_INUSE);
 419         netif_start_queue(dev);
 420         return 0;
 421 }
 422
 423 /* Hook the destructor so we can free slcan devs at the right point in time */
 424 static void slc_free_netdev(struct net_device *dev)
 425 {
 426         int i = dev->base_addr;
 427         free_netdev(dev);
 428         slcan_devs[i] = NULL;
 429 }
 430
 431 static int slcan_change_mtu(struct net_device *dev, int new_mtu)
 432 {
 433         return -EINVAL;
 434 }
 435
 436 static const struct net_device_ops slc_netdev_ops = {
 437         .ndo_open               = slc_open,
 438         .ndo_stop               = slc_close,
 439         .ndo_start_xmit         = slc_xmit,
 440         .ndo_change_mtu         = slcan_change_mtu,
 441 };
 442
 443 static void slc_setup(struct net_device *dev)
 444 {
 445         dev->netdev_ops         = &slc_netdev_ops;
 446         dev->destructor         = slc_free_netdev;
 447
 448         dev->hard_header_len    = 0;
 449         dev->addr_len           = 0;
 450         dev->tx_queue_len       = 10;
 451
 452         dev->mtu                = sizeof(struct can_frame);
 453         dev->type               = ARPHRD_CAN;
 454
 455         /* New-style flags. */
 456         dev->flags              = IFF_NOARP;
 457         dev->features           = NETIF_F_HW_CSUM;
 458 }
 459
 460 /******************************************
 461   Routines looking at TTY side.
 462  ******************************************/
 463
 464 /*
 465  * Handle the 'receiver data ready' interrupt.
 466  * This function is called by the 'tty_io' module in the kernel when
 467  * a block of SLCAN data has been received, which can now be decapsulated
 468  * and sent on to some IP layer for further processing. This will not
 469  * be re-entered while running but other ldisc functions may be called
 470  * in parallel
 471  */
 472
 473 static void slcan_receive_buf(struct tty_struct *tty,
 474                               const unsigned char *cp, char *fp, int count)
 475 {
 476         struct slcan *sl = (struct slcan *) tty->disc_data;
 477
 478         if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
 479                 return;
 480
 481         /* Read the characters out of the buffer */
 482         while (count--) {
 483                 if (fp && *fp++) {
 484                         if (!test_and_set_bit(SLF_ERROR, &sl->flags))
 485                                 sl->dev->stats.rx_errors++;
 486                         cp++;
 487                         continue;
 488                 }
 489                 slcan_unesc(sl, *cp++);
 490         }
 491 }
 492
 493 /************************************
 494  *  slcan_open helper routines.
 495  ************************************/
 496
 497 /* Collect hanged up channels */
 498 static void slc_sync(void)
 499 {
 500         int i;
 501         struct net_device *dev;
 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                 sl = netdev_priv(dev);
 510                 if (sl->tty)
 511                         continue;
 512                 if (dev->flags & IFF_UP)
 513                         dev_close(dev);
 514         }
 515 }
 516
 517 /* Find a free SLCAN channel, and link in this `tty' line. */
 518 static struct slcan *slc_alloc(dev_t line)
 519 {
 520         int i;
 521         char name[IFNAMSIZ];
 522         struct net_device *dev = NULL;
 523         struct slcan       *sl;
 524
 525         for (i = 0; i < maxdev; i++) {
 526                 dev = slcan_devs[i];
 527                 if (dev == NULL)
 528                         break;
 529
 530         }
 531
 532         /* Sorry, too many, all slots in use */
 533         if (i >= maxdev)
 534                 return NULL;
 535
 536         sprintf(name, "slcan%d", i);
 537         dev = alloc_netdev(sizeof(*sl), name, slc_setup);
 538         if (!dev)
 539                 return NULL;
 540
 541         dev->base_addr  = i;
 542         sl = netdev_priv(dev);
 543
 544         /* Initialize channel control data */
 545         sl->magic = SLCAN_MAGIC;
 546         sl->dev = dev;
 547         spin_lock_init(&sl->lock);
 548         INIT_WORK(&sl->tx_work, slcan_transmit);
 549         slcan_devs[i] = dev;
 550
 551         return sl;
 552 }
 553
 554 /*
 555  * Open the high-level part of the SLCAN channel.
 556  * This function is called by the TTY module when the
 557  * SLCAN line discipline is called for.  Because we are
 558  * sure the tty line exists, we only have to link it to
 559  * a free SLCAN channel...
 560  *
 561  * Called in process context serialized from other ldisc calls.
 562  */
 563
 564 static int slcan_open(struct tty_struct *tty)
 565 {
 566         struct slcan *sl;
 567         int err;
 568
 569         if (!capable(CAP_NET_ADMIN))
 570                 return -EPERM;
 571
 572         if (tty->ops->write == NULL)
 573                 return -EOPNOTSUPP;
 574
 575         /* RTnetlink lock is misused here to serialize concurrent
 576            opens of slcan channels. There are better ways, but it is
 577            the simplest one.
 578          */
 579         rtnl_lock();
 580
 581         /* Collect hanged up channels. */
 582         slc_sync();
 583
 584         sl = tty->disc_data;
 585
 586         err = -EEXIST;
 587         /* First make sure we're not already connected. */
 588         if (sl && sl->magic == SLCAN_MAGIC)
 589                 goto err_exit;
 590
 591         /* OK.  Find a free SLCAN channel to use. */
 592         err = -ENFILE;
 593         sl = slc_alloc(tty_devnum(tty));
 594         if (sl == NULL)
 595                 goto err_exit;
 596
 597         sl->tty = tty;
 598         tty->disc_data = sl;
 599
 600         if (!test_bit(SLF_INUSE, &sl->flags)) {
 601                 /* Perform the low-level SLCAN initialization. */
 602                 sl->rcount   = 0;
 603                 sl->xleft    = 0;
 604
 605                 set_bit(SLF_INUSE, &sl->flags);
 606
 607                 err = register_netdevice(sl->dev);
 608                 if (err)
 609                         goto err_free_chan;
 610         }
 611
 612         /* Done.  We have linked the TTY line to a channel. */
 613         rtnl_unlock();
 614         tty->receive_room = 65536;      /* We don't flow control */
 615
 616         /* TTY layer expects 0 on success */
 617         return 0;
 618
 619 err_free_chan:
 620         sl->tty = NULL;
 621         tty->disc_data = NULL;
 622         clear_bit(SLF_INUSE, &sl->flags);
 623         /* do not call free_netdev before rtnl_unlock */
 624         rtnl_unlock();
 625         slc_free_netdev(sl->dev);
 626         return err;
 627
 628 err_exit:
 629         rtnl_unlock();
 630
 631         /* Count references from TTY module */
 632         return err;
 633 }
 634
 635 /*
 636  * Close down a SLCAN channel.
 637  * This means flushing out any pending queues, and then returning. This
 638  * call is serialized against other ldisc functions.
 639  *
 640  * We also use this method for a hangup event.
 641  */
 642
 643 static void slcan_close(struct tty_struct *tty)
 644 {
 645         struct slcan *sl = (struct slcan *) tty->disc_data;
 646
 647         /* First make sure we're connected. */
 648         if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
 649                 return;
 650
 651         spin_lock_bh(&sl->lock);
 652         rcu_assign_pointer(tty->disc_data, NULL);
 653         sl->tty = NULL;
 654         spin_unlock_bh(&sl->lock);
 655
 656         synchronize_rcu();
 657         flush_work(&sl->tx_work);
 658
 659         /* Flush network side */
 660         unregister_netdev(sl->dev);
 661         /* This will complete via sl_free_netdev */
 662 }
 663
 664 static int slcan_hangup(struct tty_struct *tty)
 665 {
 666         slcan_close(tty);
 667         return 0;
 668 }
 669
 670 /* Perform I/O control on an active SLCAN channel. */
 671 static int slcan_ioctl(struct tty_struct *tty, struct file *file,
 672                        unsigned int cmd, unsigned long arg)
 673 {
 674         struct slcan *sl = (struct slcan *) tty->disc_data;
 675         unsigned int tmp;
 676
 677         /* First make sure we're connected. */
 678         if (!sl || sl->magic != SLCAN_MAGIC)
 679                 return -EINVAL;
 680
 681         switch (cmd) {
 682         case SIOCGIFNAME:
 683                 tmp = strlen(sl->dev->name) + 1;
 684                 if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
 685                         return -EFAULT;
 686                 return 0;
 687
 688         case SIOCSIFHWADDR:
 689                 return -EINVAL;
 690
 691         default:
 692                 return tty_mode_ioctl(tty, file, cmd, arg);
 693         }
 694 }
 695
 696 static struct tty_ldisc_ops slc_ldisc = {
 697         .owner          = THIS_MODULE,
 698         .magic          = TTY_LDISC_MAGIC,
 699         .name           = "slcan",
 700         .open           = slcan_open,
 701         .close          = slcan_close,
 702         .hangup         = slcan_hangup,
 703         .ioctl          = slcan_ioctl,
 704         .receive_buf    = slcan_receive_buf,
 705         .write_wakeup   = slcan_write_wakeup,
 706 };
 707
 708 static int __init slcan_init(void)
 709 {
 710         int status;
 711
 712         if (maxdev < 4)
 713                 maxdev = 4; /* Sanity */
 714
 715         printk(banner);
 716         printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);
 717
 718         slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
 719         if (!slcan_devs)
 720                 return -ENOMEM;
 721
 722         /* Fill in our line protocol discipline, and register it */
 723         status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
 724         if (status)  {
 725                 printk(KERN_ERR "slcan: can't register line discipline\n");
 726                 kfree(slcan_devs);
 727         }
 728         return status;
 729 }
 730
 731 static void __exit slcan_exit(void)
 732 {
 733         int i;
 734         struct net_device *dev;
 735         struct slcan *sl;
 736         unsigned long timeout = jiffies + HZ;
 737         int busy = 0;
 738
 739         if (slcan_devs == NULL)
 740                 return;
 741
 742         /* First of all: check for active disciplines and hangup them.
 743          */
 744         do {
 745                 if (busy)
 746                         msleep_interruptible(100);
 747
 748                 busy = 0;
 749                 for (i = 0; i < maxdev; i++) {
 750                         dev = slcan_devs[i];
 751                         if (!dev)
 752                                 continue;
 753                         sl = netdev_priv(dev);
 754                         spin_lock_bh(&sl->lock);
 755                         if (sl->tty) {
 756                                 busy++;
 757                                 tty_hangup(sl->tty);
 758                         }
 759                         spin_unlock_bh(&sl->lock);
 760                 }
 761         } while (busy && time_before(jiffies, timeout));
 762
 763         /* FIXME: hangup is async so we should wait when doing this second
 764            phase */
 765
 766         for (i = 0; i < maxdev; i++) {
 767                 dev = slcan_devs[i];
 768                 if (!dev)
 769                         continue;
 770                 slcan_devs[i] = NULL;
 771
 772                 sl = netdev_priv(dev);
 773                 if (sl->tty) {
 774                         printk(KERN_ERR "%s: tty discipline still running\n",
 775                                dev->name);
 776                         /* Intentionally leak the control block. */
 777                         dev->destructor = NULL;
 778                 }
 779
 780                 unregister_netdev(dev);
 781         }
 782
 783         kfree(slcan_devs);
 784         slcan_devs = NULL;
 785
 786         i = tty_unregister_ldisc(N_SLCAN);
 787         if (i)
 788                 printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
 789 }
 790
 791 module_init(slcan_init);
 792 module_exit(slcan_exit);