slcan.c revision c477ebd89db4f53b380b6ba70d25e055e0aa2739
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 59static __initconst const char banner[] = 60 KERN_INFO "slcan: serial line CAN interface driver\n"; 61 62MODULE_ALIAS_LDISC(N_SLCAN); 63MODULE_DESCRIPTION("serial line CAN interface"); 64MODULE_LICENSE("GPL"); 65MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>"); 66 67#define SLCAN_MAGIC 0x53CA 68 69static int maxdev = 10; /* MAX number of SLCAN channels; 70 This can be overridden with 71 insmod slcan.ko maxdev=nnn */ 72module_param(maxdev, int, 0); 73MODULE_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 78struct 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 98static 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 */ 140static 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 */ 204static 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. */ 231static 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 */ 274static 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. */ 298static 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 320out: 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 */ 331static 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 */ 349static 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 */ 362static 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 369static 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 375static 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 405static 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 */ 430static 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. */ 450static 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 495static 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 550err_free_chan: 551 sl->tty = NULL; 552 tty->disc_data = NULL; 553 clear_bit(SLF_INUSE, &sl->flags); 554 555err_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 570static 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 586static 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. */ 593static 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 618static 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 630static 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 653static 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 713module_init(slcan_init); 714module_exit(slcan_exit); 715