1 /* generic HDLC line discipline for Linux 2 * 3 * Written by Paul Fulghum paulkf@microgate.com 4 * for Microgate Corporation 5 * 6 * Microgate and SyncLink are registered trademarks of Microgate Corporation 7 * 8 * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>, 9 * Al Longyear <longyear@netcom.com>, 10 * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au> 11 * 12 * Original release 01/11/99 13 * 14 * This code is released under the GNU General Public License (GPL) 15 * 16 * This module implements the tty line discipline N_HDLC for use with 17 * tty device drivers that support bit-synchronous HDLC communications. 18 * 19 * All HDLC data is frame oriented which means: 20 * 21 * 1. tty write calls represent one complete transmit frame of data 22 * The device driver should accept the complete frame or none of 23 * the frame (busy) in the write method. Each write call should have 24 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame 25 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535 26 * should include any crc bytes required. For example, when using 27 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame 28 * the application may transmit is limited to 65531 bytes. For CCITT 29 * CRC16, the maximum application frame size would be 65533. 30 * 31 * 32 * 2. receive callbacks from the device driver represents 33 * one received frame. The device driver should bypass 34 * the tty flip buffer and call the line discipline receive 35 * callback directly to avoid fragmenting or concatenating 36 * multiple frames into a single receive callback. 37 * 38 * The HDLC line discipline queues the receive frames in separate 39 * buffers so complete receive frames can be returned by the 40 * tty read calls. 41 * 42 * 3. tty read calls returns an entire frame of data or nothing. 43 * 44 * 4. all send and receive data is considered raw. No processing 45 * or translation is performed by the line discipline, regardless 46 * of the tty flags 47 * 48 * 5. When line discipline is queried for the amount of receive 49 * data available (FIOC), 0 is returned if no data available, 50 * otherwise the count of the next available frame is returned. 51 * (instead of the sum of all received frame counts). 52 * 53 * These conventions allow the standard tty programming interface 54 * to be used for synchronous HDLC applications when used with 55 * this line discipline (or another line discipline that is frame 56 * oriented such as N_PPP). 57 * 58 * The SyncLink driver (synclink.c) implements both asynchronous 59 * (using standard line discipline N_TTY) and synchronous HDLC 60 * (using N_HDLC) communications, with the latter using the above 61 * conventions. 62 * 63 * This implementation is very basic and does not maintain 64 * any statistics. The main point is to enforce the raw data 65 * and frame orientation of HDLC communications. 66 * 67 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED 68 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 69 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 70 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, 71 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 72 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 73 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 74 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 75 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 76 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 77 * OF THE POSSIBILITY OF SUCH DAMAGE. 78 */ 79 80 #define HDLC_MAGIC 0x239e 81 82 #include <linux/module.h> 83 #include <linux/init.h> 84 #include <linux/kernel.h> 85 #include <linux/sched.h> 86 #include <linux/types.h> 87 #include <linux/fcntl.h> 88 #include <linux/interrupt.h> 89 #include <linux/ptrace.h> 90 91 #undef VERSION 92 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch)) 93 94 #include <linux/poll.h> 95 #include <linux/in.h> 96 #include <linux/ioctl.h> 97 #include <linux/slab.h> 98 #include <linux/tty.h> 99 #include <linux/errno.h> 100 #include <linux/string.h> /* used in new tty drivers */ 101 #include <linux/signal.h> /* used in new tty drivers */ 102 #include <linux/if.h> 103 #include <linux/bitops.h> 104 105 #include <asm/termios.h> 106 #include <linux/uaccess.h> 107 108 /* 109 * Buffers for individual HDLC frames 110 */ 111 #define MAX_HDLC_FRAME_SIZE 65535 112 #define DEFAULT_RX_BUF_COUNT 10 113 #define MAX_RX_BUF_COUNT 60 114 #define DEFAULT_TX_BUF_COUNT 3 115 116 struct n_hdlc_buf { 117 struct n_hdlc_buf *link; 118 int count; 119 char buf[1]; 120 }; 121 122 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe) 123 124 struct n_hdlc_buf_list { 125 struct n_hdlc_buf *head; 126 struct n_hdlc_buf *tail; 127 int count; 128 spinlock_t spinlock; 129 }; 130 131 /** 132 * struct n_hdlc - per device instance data structure 133 * @magic - magic value for structure 134 * @flags - miscellaneous control flags 135 * @tty - ptr to TTY structure 136 * @backup_tty - TTY to use if tty gets closed 137 * @tbusy - reentrancy flag for tx wakeup code 138 * @woke_up - FIXME: describe this field 139 * @tbuf - currently transmitting tx buffer 140 * @tx_buf_list - list of pending transmit frame buffers 141 * @rx_buf_list - list of received frame buffers 142 * @tx_free_buf_list - list unused transmit frame buffers 143 * @rx_free_buf_list - list unused received frame buffers 144 */ 145 struct n_hdlc { 146 int magic; 147 __u32 flags; 148 struct tty_struct *tty; 149 struct tty_struct *backup_tty; 150 int tbusy; 151 int woke_up; 152 struct n_hdlc_buf *tbuf; 153 struct n_hdlc_buf_list tx_buf_list; 154 struct n_hdlc_buf_list rx_buf_list; 155 struct n_hdlc_buf_list tx_free_buf_list; 156 struct n_hdlc_buf_list rx_free_buf_list; 157 }; 158 159 /* 160 * HDLC buffer list manipulation functions 161 */ 162 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, 163 struct n_hdlc_buf *buf); 164 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); 165 166 /* Local functions */ 167 168 static struct n_hdlc *n_hdlc_alloc (void); 169 170 /* debug level can be set by insmod for debugging purposes */ 171 #define DEBUG_LEVEL_INFO 1 172 static int debuglevel; 173 174 /* max frame size for memory allocations */ 175 static int maxframe = 4096; 176 177 /* TTY callbacks */ 178 179 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, 180 __u8 __user *buf, size_t nr); 181 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, 182 const unsigned char *buf, size_t nr); 183 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, 184 unsigned int cmd, unsigned long arg); 185 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, 186 poll_table *wait); 187 static int n_hdlc_tty_open(struct tty_struct *tty); 188 static void n_hdlc_tty_close(struct tty_struct *tty); 189 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp, 190 char *fp, int count); 191 static void n_hdlc_tty_wakeup(struct tty_struct *tty); 192 193 #define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f))) 194 195 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data)) 196 #define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty) 197 198 static void flush_rx_queue(struct tty_struct *tty) 199 { 200 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 201 struct n_hdlc_buf *buf; 202 203 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list))) 204 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf); 205 } 206 207 static void flush_tx_queue(struct tty_struct *tty) 208 { 209 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 210 struct n_hdlc_buf *buf; 211 unsigned long flags; 212 213 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) 214 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); 215 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 216 if (n_hdlc->tbuf) { 217 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf); 218 n_hdlc->tbuf = NULL; 219 } 220 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 221 } 222 223 static struct tty_ldisc_ops n_hdlc_ldisc = { 224 .owner = THIS_MODULE, 225 .magic = TTY_LDISC_MAGIC, 226 .name = "hdlc", 227 .open = n_hdlc_tty_open, 228 .close = n_hdlc_tty_close, 229 .read = n_hdlc_tty_read, 230 .write = n_hdlc_tty_write, 231 .ioctl = n_hdlc_tty_ioctl, 232 .poll = n_hdlc_tty_poll, 233 .receive_buf = n_hdlc_tty_receive, 234 .write_wakeup = n_hdlc_tty_wakeup, 235 .flush_buffer = flush_rx_queue, 236 }; 237 238 /** 239 * n_hdlc_release - release an n_hdlc per device line discipline info structure 240 * @n_hdlc - per device line discipline info structure 241 */ 242 static void n_hdlc_release(struct n_hdlc *n_hdlc) 243 { 244 struct tty_struct *tty = n_hdlc2tty (n_hdlc); 245 struct n_hdlc_buf *buf; 246 247 if (debuglevel >= DEBUG_LEVEL_INFO) 248 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__); 249 250 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */ 251 wake_up_interruptible (&tty->read_wait); 252 wake_up_interruptible (&tty->write_wait); 253 254 if (tty->disc_data == n_hdlc) 255 tty->disc_data = NULL; /* Break the tty->n_hdlc link */ 256 257 /* Release transmit and receive buffers */ 258 for(;;) { 259 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); 260 if (buf) { 261 kfree(buf); 262 } else 263 break; 264 } 265 for(;;) { 266 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); 267 if (buf) { 268 kfree(buf); 269 } else 270 break; 271 } 272 for(;;) { 273 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); 274 if (buf) { 275 kfree(buf); 276 } else 277 break; 278 } 279 for(;;) { 280 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 281 if (buf) { 282 kfree(buf); 283 } else 284 break; 285 } 286 kfree(n_hdlc->tbuf); 287 kfree(n_hdlc); 288 289 } /* end of n_hdlc_release() */ 290 291 /** 292 * n_hdlc_tty_close - line discipline close 293 * @tty - pointer to tty info structure 294 * 295 * Called when the line discipline is changed to something 296 * else, the tty is closed, or the tty detects a hangup. 297 */ 298 static void n_hdlc_tty_close(struct tty_struct *tty) 299 { 300 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 301 302 if (debuglevel >= DEBUG_LEVEL_INFO) 303 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__); 304 305 if (n_hdlc != NULL) { 306 if (n_hdlc->magic != HDLC_MAGIC) { 307 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n"); 308 return; 309 } 310 #if defined(TTY_NO_WRITE_SPLIT) 311 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags); 312 #endif 313 tty->disc_data = NULL; 314 if (tty == n_hdlc->backup_tty) 315 n_hdlc->backup_tty = NULL; 316 if (tty != n_hdlc->tty) 317 return; 318 if (n_hdlc->backup_tty) { 319 n_hdlc->tty = n_hdlc->backup_tty; 320 } else { 321 n_hdlc_release (n_hdlc); 322 } 323 } 324 325 if (debuglevel >= DEBUG_LEVEL_INFO) 326 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__); 327 328 } /* end of n_hdlc_tty_close() */ 329 330 /** 331 * n_hdlc_tty_open - called when line discipline changed to n_hdlc 332 * @tty - pointer to tty info structure 333 * 334 * Returns 0 if success, otherwise error code 335 */ 336 static int n_hdlc_tty_open (struct tty_struct *tty) 337 { 338 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 339 340 if (debuglevel >= DEBUG_LEVEL_INFO) 341 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n", 342 __FILE__,__LINE__, 343 tty->name); 344 345 /* There should not be an existing table for this slot. */ 346 if (n_hdlc) { 347 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" ); 348 return -EEXIST; 349 } 350 351 n_hdlc = n_hdlc_alloc(); 352 if (!n_hdlc) { 353 printk (KERN_ERR "n_hdlc_alloc failed\n"); 354 return -ENFILE; 355 } 356 357 tty->disc_data = n_hdlc; 358 n_hdlc->tty = tty; 359 tty->receive_room = 65536; 360 361 #if defined(TTY_NO_WRITE_SPLIT) 362 /* change tty_io write() to not split large writes into 8K chunks */ 363 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags); 364 #endif 365 366 /* flush receive data from driver */ 367 tty_driver_flush_buffer(tty); 368 369 if (debuglevel >= DEBUG_LEVEL_INFO) 370 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__); 371 372 return 0; 373 374 } /* end of n_tty_hdlc_open() */ 375 376 /** 377 * n_hdlc_send_frames - send frames on pending send buffer list 378 * @n_hdlc - pointer to ldisc instance data 379 * @tty - pointer to tty instance data 380 * 381 * Send frames on pending send buffer list until the driver does not accept a 382 * frame (busy) this function is called after adding a frame to the send buffer 383 * list and by the tty wakeup callback. 384 */ 385 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) 386 { 387 register int actual; 388 unsigned long flags; 389 struct n_hdlc_buf *tbuf; 390 391 if (debuglevel >= DEBUG_LEVEL_INFO) 392 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__); 393 check_again: 394 395 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 396 if (n_hdlc->tbusy) { 397 n_hdlc->woke_up = 1; 398 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 399 return; 400 } 401 n_hdlc->tbusy = 1; 402 n_hdlc->woke_up = 0; 403 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 404 405 /* get current transmit buffer or get new transmit */ 406 /* buffer from list of pending transmit buffers */ 407 408 tbuf = n_hdlc->tbuf; 409 if (!tbuf) 410 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 411 412 while (tbuf) { 413 if (debuglevel >= DEBUG_LEVEL_INFO) 414 printk("%s(%d)sending frame %p, count=%d\n", 415 __FILE__,__LINE__,tbuf,tbuf->count); 416 417 /* Send the next block of data to device */ 418 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 419 actual = tty->ops->write(tty, tbuf->buf, tbuf->count); 420 421 /* rollback was possible and has been done */ 422 if (actual == -ERESTARTSYS) { 423 n_hdlc->tbuf = tbuf; 424 break; 425 } 426 /* if transmit error, throw frame away by */ 427 /* pretending it was accepted by driver */ 428 if (actual < 0) 429 actual = tbuf->count; 430 431 if (actual == tbuf->count) { 432 if (debuglevel >= DEBUG_LEVEL_INFO) 433 printk("%s(%d)frame %p completed\n", 434 __FILE__,__LINE__,tbuf); 435 436 /* free current transmit buffer */ 437 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf); 438 439 /* this tx buffer is done */ 440 n_hdlc->tbuf = NULL; 441 442 /* wait up sleeping writers */ 443 wake_up_interruptible(&tty->write_wait); 444 445 /* get next pending transmit buffer */ 446 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 447 } else { 448 if (debuglevel >= DEBUG_LEVEL_INFO) 449 printk("%s(%d)frame %p pending\n", 450 __FILE__,__LINE__,tbuf); 451 452 /* buffer not accepted by driver */ 453 /* set this buffer as pending buffer */ 454 n_hdlc->tbuf = tbuf; 455 break; 456 } 457 } 458 459 if (!tbuf) 460 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 461 462 /* Clear the re-entry flag */ 463 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 464 n_hdlc->tbusy = 0; 465 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 466 467 if (n_hdlc->woke_up) 468 goto check_again; 469 470 if (debuglevel >= DEBUG_LEVEL_INFO) 471 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__); 472 473 } /* end of n_hdlc_send_frames() */ 474 475 /** 476 * n_hdlc_tty_wakeup - Callback for transmit wakeup 477 * @tty - pointer to associated tty instance data 478 * 479 * Called when low level device driver can accept more send data. 480 */ 481 static void n_hdlc_tty_wakeup(struct tty_struct *tty) 482 { 483 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 484 485 if (debuglevel >= DEBUG_LEVEL_INFO) 486 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__); 487 488 if (!n_hdlc) 489 return; 490 491 if (tty != n_hdlc->tty) { 492 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 493 return; 494 } 495 496 n_hdlc_send_frames (n_hdlc, tty); 497 498 } /* end of n_hdlc_tty_wakeup() */ 499 500 /** 501 * n_hdlc_tty_receive - Called by tty driver when receive data is available 502 * @tty - pointer to tty instance data 503 * @data - pointer to received data 504 * @flags - pointer to flags for data 505 * @count - count of received data in bytes 506 * 507 * Called by tty low level driver when receive data is available. Data is 508 * interpreted as one HDLC frame. 509 */ 510 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data, 511 char *flags, int count) 512 { 513 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 514 register struct n_hdlc_buf *buf; 515 516 if (debuglevel >= DEBUG_LEVEL_INFO) 517 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n", 518 __FILE__,__LINE__, count); 519 520 /* This can happen if stuff comes in on the backup tty */ 521 if (!n_hdlc || tty != n_hdlc->tty) 522 return; 523 524 /* verify line is using HDLC discipline */ 525 if (n_hdlc->magic != HDLC_MAGIC) { 526 printk("%s(%d) line not using HDLC discipline\n", 527 __FILE__,__LINE__); 528 return; 529 } 530 531 if ( count>maxframe ) { 532 if (debuglevel >= DEBUG_LEVEL_INFO) 533 printk("%s(%d) rx count>maxframesize, data discarded\n", 534 __FILE__,__LINE__); 535 return; 536 } 537 538 /* get a free HDLC buffer */ 539 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); 540 if (!buf) { 541 /* no buffers in free list, attempt to allocate another rx buffer */ 542 /* unless the maximum count has been reached */ 543 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT) 544 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC); 545 } 546 547 if (!buf) { 548 if (debuglevel >= DEBUG_LEVEL_INFO) 549 printk("%s(%d) no more rx buffers, data discarded\n", 550 __FILE__,__LINE__); 551 return; 552 } 553 554 /* copy received data to HDLC buffer */ 555 memcpy(buf->buf,data,count); 556 buf->count=count; 557 558 /* add HDLC buffer to list of received frames */ 559 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf); 560 561 /* wake up any blocked reads and perform async signalling */ 562 wake_up_interruptible (&tty->read_wait); 563 if (n_hdlc->tty->fasync != NULL) 564 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN); 565 566 } /* end of n_hdlc_tty_receive() */ 567 568 /** 569 * n_hdlc_tty_read - Called to retrieve one frame of data (if available) 570 * @tty - pointer to tty instance data 571 * @file - pointer to open file object 572 * @buf - pointer to returned data buffer 573 * @nr - size of returned data buffer 574 * 575 * Returns the number of bytes returned or error code. 576 */ 577 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, 578 __u8 __user *buf, size_t nr) 579 { 580 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 581 int ret = 0; 582 struct n_hdlc_buf *rbuf; 583 DECLARE_WAITQUEUE(wait, current); 584 585 if (debuglevel >= DEBUG_LEVEL_INFO) 586 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__); 587 588 /* Validate the pointers */ 589 if (!n_hdlc) 590 return -EIO; 591 592 /* verify user access to buffer */ 593 if (!access_ok(VERIFY_WRITE, buf, nr)) { 594 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user " 595 "buffer\n", __FILE__, __LINE__); 596 return -EFAULT; 597 } 598 599 add_wait_queue(&tty->read_wait, &wait); 600 601 for (;;) { 602 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { 603 ret = -EIO; 604 break; 605 } 606 if (tty_hung_up_p(file)) 607 break; 608 609 set_current_state(TASK_INTERRUPTIBLE); 610 611 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); 612 if (rbuf) { 613 if (rbuf->count > nr) { 614 /* too large for caller's buffer */ 615 ret = -EOVERFLOW; 616 } else { 617 if (copy_to_user(buf, rbuf->buf, rbuf->count)) 618 ret = -EFAULT; 619 else 620 ret = rbuf->count; 621 } 622 623 if (n_hdlc->rx_free_buf_list.count > 624 DEFAULT_RX_BUF_COUNT) 625 kfree(rbuf); 626 else 627 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf); 628 break; 629 } 630 631 /* no data */ 632 if (file->f_flags & O_NONBLOCK) { 633 ret = -EAGAIN; 634 break; 635 } 636 637 schedule(); 638 639 if (signal_pending(current)) { 640 ret = -EINTR; 641 break; 642 } 643 } 644 645 remove_wait_queue(&tty->read_wait, &wait); 646 __set_current_state(TASK_RUNNING); 647 648 return ret; 649 650 } /* end of n_hdlc_tty_read() */ 651 652 /** 653 * n_hdlc_tty_write - write a single frame of data to device 654 * @tty - pointer to associated tty device instance data 655 * @file - pointer to file object data 656 * @data - pointer to transmit data (one frame) 657 * @count - size of transmit frame in bytes 658 * 659 * Returns the number of bytes written (or error code). 660 */ 661 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, 662 const unsigned char *data, size_t count) 663 { 664 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 665 int error = 0; 666 DECLARE_WAITQUEUE(wait, current); 667 struct n_hdlc_buf *tbuf; 668 669 if (debuglevel >= DEBUG_LEVEL_INFO) 670 printk("%s(%d)n_hdlc_tty_write() called count=%zd\n", 671 __FILE__,__LINE__,count); 672 673 /* Verify pointers */ 674 if (!n_hdlc) 675 return -EIO; 676 677 if (n_hdlc->magic != HDLC_MAGIC) 678 return -EIO; 679 680 /* verify frame size */ 681 if (count > maxframe ) { 682 if (debuglevel & DEBUG_LEVEL_INFO) 683 printk (KERN_WARNING 684 "n_hdlc_tty_write: truncating user packet " 685 "from %lu to %d\n", (unsigned long) count, 686 maxframe ); 687 count = maxframe; 688 } 689 690 add_wait_queue(&tty->write_wait, &wait); 691 692 for (;;) { 693 set_current_state(TASK_INTERRUPTIBLE); 694 695 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); 696 if (tbuf) 697 break; 698 699 if (file->f_flags & O_NONBLOCK) { 700 error = -EAGAIN; 701 break; 702 } 703 schedule(); 704 705 n_hdlc = tty2n_hdlc (tty); 706 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 707 tty != n_hdlc->tty) { 708 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc); 709 error = -EIO; 710 break; 711 } 712 713 if (signal_pending(current)) { 714 error = -EINTR; 715 break; 716 } 717 } 718 719 __set_current_state(TASK_RUNNING); 720 remove_wait_queue(&tty->write_wait, &wait); 721 722 if (!error) { 723 /* Retrieve the user's buffer */ 724 memcpy(tbuf->buf, data, count); 725 726 /* Send the data */ 727 tbuf->count = error = count; 728 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf); 729 n_hdlc_send_frames(n_hdlc,tty); 730 } 731 732 return error; 733 734 } /* end of n_hdlc_tty_write() */ 735 736 /** 737 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device. 738 * @tty - pointer to tty instance data 739 * @file - pointer to open file object for device 740 * @cmd - IOCTL command code 741 * @arg - argument for IOCTL call (cmd dependent) 742 * 743 * Returns command dependent result. 744 */ 745 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, 746 unsigned int cmd, unsigned long arg) 747 { 748 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 749 int error = 0; 750 int count; 751 unsigned long flags; 752 753 if (debuglevel >= DEBUG_LEVEL_INFO) 754 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n", 755 __FILE__,__LINE__,cmd); 756 757 /* Verify the status of the device */ 758 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC) 759 return -EBADF; 760 761 switch (cmd) { 762 case FIONREAD: 763 /* report count of read data available */ 764 /* in next available frame (if any) */ 765 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags); 766 if (n_hdlc->rx_buf_list.head) 767 count = n_hdlc->rx_buf_list.head->count; 768 else 769 count = 0; 770 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags); 771 error = put_user(count, (int __user *)arg); 772 break; 773 774 case TIOCOUTQ: 775 /* get the pending tx byte count in the driver */ 776 count = tty_chars_in_buffer(tty); 777 /* add size of next output frame in queue */ 778 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags); 779 if (n_hdlc->tx_buf_list.head) 780 count += n_hdlc->tx_buf_list.head->count; 781 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags); 782 error = put_user(count, (int __user *)arg); 783 break; 784 785 case TCFLSH: 786 switch (arg) { 787 case TCIOFLUSH: 788 case TCOFLUSH: 789 flush_tx_queue(tty); 790 } 791 /* fall through to default */ 792 793 default: 794 error = n_tty_ioctl_helper(tty, file, cmd, arg); 795 break; 796 } 797 return error; 798 799 } /* end of n_hdlc_tty_ioctl() */ 800 801 /** 802 * n_hdlc_tty_poll - TTY callback for poll system call 803 * @tty - pointer to tty instance data 804 * @filp - pointer to open file object for device 805 * @poll_table - wait queue for operations 806 * 807 * Determine which operations (read/write) will not block and return info 808 * to caller. 809 * Returns a bit mask containing info on which ops will not block. 810 */ 811 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, 812 poll_table *wait) 813 { 814 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 815 unsigned int mask = 0; 816 817 if (debuglevel >= DEBUG_LEVEL_INFO) 818 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__); 819 820 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) { 821 /* queue current process into any wait queue that */ 822 /* may awaken in the future (read and write) */ 823 824 poll_wait(filp, &tty->read_wait, wait); 825 poll_wait(filp, &tty->write_wait, wait); 826 827 /* set bits for operations that won't block */ 828 if (n_hdlc->rx_buf_list.head) 829 mask |= POLLIN | POLLRDNORM; /* readable */ 830 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) 831 mask |= POLLHUP; 832 if (tty_hung_up_p(filp)) 833 mask |= POLLHUP; 834 if (!tty_is_writelocked(tty) && 835 n_hdlc->tx_free_buf_list.head) 836 mask |= POLLOUT | POLLWRNORM; /* writable */ 837 } 838 return mask; 839 } /* end of n_hdlc_tty_poll() */ 840 841 /** 842 * n_hdlc_alloc - allocate an n_hdlc instance data structure 843 * 844 * Returns a pointer to newly created structure if success, otherwise %NULL 845 */ 846 static struct n_hdlc *n_hdlc_alloc(void) 847 { 848 struct n_hdlc_buf *buf; 849 int i; 850 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL); 851 852 if (!n_hdlc) 853 return NULL; 854 855 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock); 856 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); 857 spin_lock_init(&n_hdlc->rx_buf_list.spinlock); 858 spin_lock_init(&n_hdlc->tx_buf_list.spinlock); 859 860 /* allocate free rx buffer list */ 861 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) { 862 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL); 863 if (buf) 864 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf); 865 else if (debuglevel >= DEBUG_LEVEL_INFO) 866 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i); 867 } 868 869 /* allocate free tx buffer list */ 870 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) { 871 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL); 872 if (buf) 873 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf); 874 else if (debuglevel >= DEBUG_LEVEL_INFO) 875 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i); 876 } 877 878 /* Initialize the control block */ 879 n_hdlc->magic = HDLC_MAGIC; 880 n_hdlc->flags = 0; 881 882 return n_hdlc; 883 884 } /* end of n_hdlc_alloc() */ 885 886 /** 887 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list 888 * @list - pointer to buffer list 889 * @buf - pointer to buffer 890 */ 891 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, 892 struct n_hdlc_buf *buf) 893 { 894 unsigned long flags; 895 spin_lock_irqsave(&list->spinlock,flags); 896 897 buf->link=NULL; 898 if (list->tail) 899 list->tail->link = buf; 900 else 901 list->head = buf; 902 list->tail = buf; 903 (list->count)++; 904 905 spin_unlock_irqrestore(&list->spinlock,flags); 906 907 } /* end of n_hdlc_buf_put() */ 908 909 /** 910 * n_hdlc_buf_get - remove and return an HDLC buffer from list 911 * @list - pointer to HDLC buffer list 912 * 913 * Remove and return an HDLC buffer from the head of the specified HDLC buffer 914 * list. 915 * Returns a pointer to HDLC buffer if available, otherwise %NULL. 916 */ 917 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list) 918 { 919 unsigned long flags; 920 struct n_hdlc_buf *buf; 921 spin_lock_irqsave(&list->spinlock,flags); 922 923 buf = list->head; 924 if (buf) { 925 list->head = buf->link; 926 (list->count)--; 927 } 928 if (!list->head) 929 list->tail = NULL; 930 931 spin_unlock_irqrestore(&list->spinlock,flags); 932 return buf; 933 934 } /* end of n_hdlc_buf_get() */ 935 936 static char hdlc_banner[] __initdata = 937 KERN_INFO "HDLC line discipline maxframe=%u\n"; 938 static char hdlc_register_ok[] __initdata = 939 KERN_INFO "N_HDLC line discipline registered.\n"; 940 static char hdlc_register_fail[] __initdata = 941 KERN_ERR "error registering line discipline: %d\n"; 942 943 static int __init n_hdlc_init(void) 944 { 945 int status; 946 947 /* range check maxframe arg */ 948 if (maxframe < 4096) 949 maxframe = 4096; 950 else if (maxframe > 65535) 951 maxframe = 65535; 952 953 printk(hdlc_banner, maxframe); 954 955 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc); 956 if (!status) 957 printk(hdlc_register_ok); 958 else 959 printk(hdlc_register_fail, status); 960 961 return status; 962 963 } /* end of init_module() */ 964 965 static char hdlc_unregister_ok[] __exitdata = 966 KERN_INFO "N_HDLC: line discipline unregistered\n"; 967 static char hdlc_unregister_fail[] __exitdata = 968 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n"; 969 970 static void __exit n_hdlc_exit(void) 971 { 972 /* Release tty registration of line discipline */ 973 int status = tty_unregister_ldisc(N_HDLC); 974 975 if (status) 976 printk(hdlc_unregister_fail, status); 977 else 978 printk(hdlc_unregister_ok); 979 } 980 981 module_init(n_hdlc_init); 982 module_exit(n_hdlc_exit); 983 984 MODULE_LICENSE("GPL"); 985 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com"); 986 module_param(debuglevel, int, 0); 987 module_param(maxframe, int, 0); 988 MODULE_ALIAS_LDISC(N_HDLC); 989