1 // SPDX-License-Identifier: GPL-1.0+ 2 /* generic HDLC line discipline for Linux 3 * 4 * Written by Paul Fulghum paulkf@microgate.com 5 * for Microgate Corporation 6 * 7 * Microgate and SyncLink are registered trademarks of Microgate Corporation 8 * 9 * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>, 10 * Al Longyear <longyear@netcom.com>, 11 * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au> 12 * 13 * Original release 01/11/99 14 * 15 * This module implements the tty line discipline N_HDLC for use with 16 * tty device drivers that support bit-synchronous HDLC communications. 17 * 18 * All HDLC data is frame oriented which means: 19 * 20 * 1. tty write calls represent one complete transmit frame of data 21 * The device driver should accept the complete frame or none of 22 * the frame (busy) in the write method. Each write call should have 23 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame 24 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535 25 * should include any crc bytes required. For example, when using 26 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame 27 * the application may transmit is limited to 65531 bytes. For CCITT 28 * CRC16, the maximum application frame size would be 65533. 29 * 30 * 31 * 2. receive callbacks from the device driver represents 32 * one received frame. The device driver should bypass 33 * the tty flip buffer and call the line discipline receive 34 * callback directly to avoid fragmenting or concatenating 35 * multiple frames into a single receive callback. 36 * 37 * The HDLC line discipline queues the receive frames in separate 38 * buffers so complete receive frames can be returned by the 39 * tty read calls. 40 * 41 * 3. tty read calls returns an entire frame of data or nothing. 42 * 43 * 4. all send and receive data is considered raw. No processing 44 * or translation is performed by the line discipline, regardless 45 * of the tty flags 46 * 47 * 5. When line discipline is queried for the amount of receive 48 * data available (FIOC), 0 is returned if no data available, 49 * otherwise the count of the next available frame is returned. 50 * (instead of the sum of all received frame counts). 51 * 52 * These conventions allow the standard tty programming interface 53 * to be used for synchronous HDLC applications when used with 54 * this line discipline (or another line discipline that is frame 55 * oriented such as N_PPP). 56 * 57 * The SyncLink driver (synclink.c) implements both asynchronous 58 * (using standard line discipline N_TTY) and synchronous HDLC 59 * (using N_HDLC) communications, with the latter using the above 60 * conventions. 61 * 62 * This implementation is very basic and does not maintain 63 * any statistics. The main point is to enforce the raw data 64 * and frame orientation of HDLC communications. 65 * 66 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED 67 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 68 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 69 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, 70 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 71 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 72 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 73 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 74 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 75 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 76 * OF THE POSSIBILITY OF SUCH DAMAGE. 77 */ 78 79 #define HDLC_MAGIC 0x239e 80 81 #include <linux/module.h> 82 #include <linux/init.h> 83 #include <linux/kernel.h> 84 #include <linux/sched.h> 85 #include <linux/types.h> 86 #include <linux/fcntl.h> 87 #include <linux/interrupt.h> 88 #include <linux/ptrace.h> 89 90 #include <linux/poll.h> 91 #include <linux/in.h> 92 #include <linux/ioctl.h> 93 #include <linux/slab.h> 94 #include <linux/tty.h> 95 #include <linux/errno.h> 96 #include <linux/string.h> /* used in new tty drivers */ 97 #include <linux/signal.h> /* used in new tty drivers */ 98 #include <linux/if.h> 99 #include <linux/bitops.h> 100 101 #include <asm/termios.h> 102 #include <linux/uaccess.h> 103 104 /* 105 * Buffers for individual HDLC frames 106 */ 107 #define MAX_HDLC_FRAME_SIZE 65535 108 #define DEFAULT_RX_BUF_COUNT 10 109 #define MAX_RX_BUF_COUNT 60 110 #define DEFAULT_TX_BUF_COUNT 3 111 112 struct n_hdlc_buf { 113 struct list_head list_item; 114 int count; 115 char buf[]; 116 }; 117 118 struct n_hdlc_buf_list { 119 struct list_head list; 120 int count; 121 spinlock_t spinlock; 122 }; 123 124 /** 125 * struct n_hdlc - per device instance data structure 126 * @magic - magic value for structure 127 * @tbusy - reentrancy flag for tx wakeup code 128 * @woke_up - tx wakeup needs to be run again as it was called while @tbusy 129 * @tx_buf_list - list of pending transmit frame buffers 130 * @rx_buf_list - list of received frame buffers 131 * @tx_free_buf_list - list unused transmit frame buffers 132 * @rx_free_buf_list - list unused received frame buffers 133 */ 134 struct n_hdlc { 135 int magic; 136 bool tbusy; 137 bool woke_up; 138 struct n_hdlc_buf_list tx_buf_list; 139 struct n_hdlc_buf_list rx_buf_list; 140 struct n_hdlc_buf_list tx_free_buf_list; 141 struct n_hdlc_buf_list rx_free_buf_list; 142 }; 143 144 /* 145 * HDLC buffer list manipulation functions 146 */ 147 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, 148 struct n_hdlc_buf *buf); 149 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, 150 struct n_hdlc_buf *buf); 151 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); 152 153 /* Local functions */ 154 155 static struct n_hdlc *n_hdlc_alloc(void); 156 157 /* max frame size for memory allocations */ 158 static int maxframe = 4096; 159 160 static void flush_rx_queue(struct tty_struct *tty) 161 { 162 struct n_hdlc *n_hdlc = tty->disc_data; 163 struct n_hdlc_buf *buf; 164 165 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list))) 166 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf); 167 } 168 169 static void flush_tx_queue(struct tty_struct *tty) 170 { 171 struct n_hdlc *n_hdlc = tty->disc_data; 172 struct n_hdlc_buf *buf; 173 174 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) 175 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); 176 } 177 178 static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list) 179 { 180 struct n_hdlc_buf *buf; 181 182 do { 183 buf = n_hdlc_buf_get(list); 184 kfree(buf); 185 } while (buf); 186 } 187 188 /** 189 * n_hdlc_tty_close - line discipline close 190 * @tty - pointer to tty info structure 191 * 192 * Called when the line discipline is changed to something 193 * else, the tty is closed, or the tty detects a hangup. 194 */ 195 static void n_hdlc_tty_close(struct tty_struct *tty) 196 { 197 struct n_hdlc *n_hdlc = tty->disc_data; 198 199 if (n_hdlc->magic != HDLC_MAGIC) { 200 pr_warn("n_hdlc: trying to close unopened tty!\n"); 201 return; 202 } 203 #if defined(TTY_NO_WRITE_SPLIT) 204 clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags); 205 #endif 206 tty->disc_data = NULL; 207 208 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */ 209 wake_up_interruptible(&tty->read_wait); 210 wake_up_interruptible(&tty->write_wait); 211 212 n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list); 213 n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list); 214 n_hdlc_free_buf_list(&n_hdlc->rx_buf_list); 215 n_hdlc_free_buf_list(&n_hdlc->tx_buf_list); 216 kfree(n_hdlc); 217 } /* end of n_hdlc_tty_close() */ 218 219 /** 220 * n_hdlc_tty_open - called when line discipline changed to n_hdlc 221 * @tty - pointer to tty info structure 222 * 223 * Returns 0 if success, otherwise error code 224 */ 225 static int n_hdlc_tty_open(struct tty_struct *tty) 226 { 227 struct n_hdlc *n_hdlc = tty->disc_data; 228 229 pr_debug("%s() called (device=%s)\n", __func__, tty->name); 230 231 /* There should not be an existing table for this slot. */ 232 if (n_hdlc) { 233 pr_err("%s: tty already associated!\n", __func__); 234 return -EEXIST; 235 } 236 237 n_hdlc = n_hdlc_alloc(); 238 if (!n_hdlc) { 239 pr_err("%s: n_hdlc_alloc failed\n", __func__); 240 return -ENFILE; 241 } 242 243 tty->disc_data = n_hdlc; 244 tty->receive_room = 65536; 245 246 /* change tty_io write() to not split large writes into 8K chunks */ 247 set_bit(TTY_NO_WRITE_SPLIT, &tty->flags); 248 249 /* flush receive data from driver */ 250 tty_driver_flush_buffer(tty); 251 252 return 0; 253 254 } /* end of n_tty_hdlc_open() */ 255 256 /** 257 * n_hdlc_send_frames - send frames on pending send buffer list 258 * @n_hdlc - pointer to ldisc instance data 259 * @tty - pointer to tty instance data 260 * 261 * Send frames on pending send buffer list until the driver does not accept a 262 * frame (busy) this function is called after adding a frame to the send buffer 263 * list and by the tty wakeup callback. 264 */ 265 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) 266 { 267 register int actual; 268 unsigned long flags; 269 struct n_hdlc_buf *tbuf; 270 271 check_again: 272 273 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 274 if (n_hdlc->tbusy) { 275 n_hdlc->woke_up = true; 276 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 277 return; 278 } 279 n_hdlc->tbusy = true; 280 n_hdlc->woke_up = false; 281 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 282 283 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 284 while (tbuf) { 285 pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count); 286 287 /* Send the next block of data to device */ 288 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 289 actual = tty->ops->write(tty, tbuf->buf, tbuf->count); 290 291 /* rollback was possible and has been done */ 292 if (actual == -ERESTARTSYS) { 293 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); 294 break; 295 } 296 /* if transmit error, throw frame away by */ 297 /* pretending it was accepted by driver */ 298 if (actual < 0) 299 actual = tbuf->count; 300 301 if (actual == tbuf->count) { 302 pr_debug("frame %p completed\n", tbuf); 303 304 /* free current transmit buffer */ 305 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf); 306 307 /* wait up sleeping writers */ 308 wake_up_interruptible(&tty->write_wait); 309 310 /* get next pending transmit buffer */ 311 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 312 } else { 313 pr_debug("frame %p pending\n", tbuf); 314 315 /* 316 * the buffer was not accepted by driver, 317 * return it back into tx queue 318 */ 319 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); 320 break; 321 } 322 } 323 324 if (!tbuf) 325 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 326 327 /* Clear the re-entry flag */ 328 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 329 n_hdlc->tbusy = false; 330 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 331 332 if (n_hdlc->woke_up) 333 goto check_again; 334 } /* end of n_hdlc_send_frames() */ 335 336 /** 337 * n_hdlc_tty_wakeup - Callback for transmit wakeup 338 * @tty - pointer to associated tty instance data 339 * 340 * Called when low level device driver can accept more send data. 341 */ 342 static void n_hdlc_tty_wakeup(struct tty_struct *tty) 343 { 344 struct n_hdlc *n_hdlc = tty->disc_data; 345 346 n_hdlc_send_frames(n_hdlc, tty); 347 } /* end of n_hdlc_tty_wakeup() */ 348 349 /** 350 * n_hdlc_tty_receive - Called by tty driver when receive data is available 351 * @tty - pointer to tty instance data 352 * @data - pointer to received data 353 * @flags - pointer to flags for data 354 * @count - count of received data in bytes 355 * 356 * Called by tty low level driver when receive data is available. Data is 357 * interpreted as one HDLC frame. 358 */ 359 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data, 360 char *flags, int count) 361 { 362 register struct n_hdlc *n_hdlc = tty->disc_data; 363 register struct n_hdlc_buf *buf; 364 365 pr_debug("%s() called count=%d\n", __func__, count); 366 367 /* verify line is using HDLC discipline */ 368 if (n_hdlc->magic != HDLC_MAGIC) { 369 pr_err("line not using HDLC discipline\n"); 370 return; 371 } 372 373 if (count > maxframe) { 374 pr_debug("rx count>maxframesize, data discarded\n"); 375 return; 376 } 377 378 /* get a free HDLC buffer */ 379 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); 380 if (!buf) { 381 /* 382 * no buffers in free list, attempt to allocate another rx 383 * buffer unless the maximum count has been reached 384 */ 385 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT) 386 buf = kmalloc(struct_size(buf, buf, maxframe), 387 GFP_ATOMIC); 388 } 389 390 if (!buf) { 391 pr_debug("no more rx buffers, data discarded\n"); 392 return; 393 } 394 395 /* copy received data to HDLC buffer */ 396 memcpy(buf->buf, data, count); 397 buf->count = count; 398 399 /* add HDLC buffer to list of received frames */ 400 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf); 401 402 /* wake up any blocked reads and perform async signalling */ 403 wake_up_interruptible(&tty->read_wait); 404 if (tty->fasync != NULL) 405 kill_fasync(&tty->fasync, SIGIO, POLL_IN); 406 407 } /* end of n_hdlc_tty_receive() */ 408 409 /** 410 * n_hdlc_tty_read - Called to retrieve one frame of data (if available) 411 * @tty - pointer to tty instance data 412 * @file - pointer to open file object 413 * @buf - pointer to returned data buffer 414 * @nr - size of returned data buffer 415 * 416 * Returns the number of bytes returned or error code. 417 */ 418 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, 419 __u8 __user *buf, size_t nr) 420 { 421 struct n_hdlc *n_hdlc = tty->disc_data; 422 int ret = 0; 423 struct n_hdlc_buf *rbuf; 424 DECLARE_WAITQUEUE(wait, current); 425 426 add_wait_queue(&tty->read_wait, &wait); 427 428 for (;;) { 429 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { 430 ret = -EIO; 431 break; 432 } 433 if (tty_hung_up_p(file)) 434 break; 435 436 set_current_state(TASK_INTERRUPTIBLE); 437 438 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); 439 if (rbuf) { 440 if (rbuf->count > nr) { 441 /* too large for caller's buffer */ 442 ret = -EOVERFLOW; 443 } else { 444 __set_current_state(TASK_RUNNING); 445 if (copy_to_user(buf, rbuf->buf, rbuf->count)) 446 ret = -EFAULT; 447 else 448 ret = rbuf->count; 449 } 450 451 if (n_hdlc->rx_free_buf_list.count > 452 DEFAULT_RX_BUF_COUNT) 453 kfree(rbuf); 454 else 455 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf); 456 break; 457 } 458 459 /* no data */ 460 if (tty_io_nonblock(tty, file)) { 461 ret = -EAGAIN; 462 break; 463 } 464 465 schedule(); 466 467 if (signal_pending(current)) { 468 ret = -EINTR; 469 break; 470 } 471 } 472 473 remove_wait_queue(&tty->read_wait, &wait); 474 __set_current_state(TASK_RUNNING); 475 476 return ret; 477 478 } /* end of n_hdlc_tty_read() */ 479 480 /** 481 * n_hdlc_tty_write - write a single frame of data to device 482 * @tty - pointer to associated tty device instance data 483 * @file - pointer to file object data 484 * @data - pointer to transmit data (one frame) 485 * @count - size of transmit frame in bytes 486 * 487 * Returns the number of bytes written (or error code). 488 */ 489 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, 490 const unsigned char *data, size_t count) 491 { 492 struct n_hdlc *n_hdlc = tty->disc_data; 493 int error = 0; 494 DECLARE_WAITQUEUE(wait, current); 495 struct n_hdlc_buf *tbuf; 496 497 pr_debug("%s() called count=%zd\n", __func__, count); 498 499 if (n_hdlc->magic != HDLC_MAGIC) 500 return -EIO; 501 502 /* verify frame size */ 503 if (count > maxframe) { 504 pr_debug("%s: truncating user packet from %zu to %d\n", 505 __func__, count, maxframe); 506 count = maxframe; 507 } 508 509 add_wait_queue(&tty->write_wait, &wait); 510 511 for (;;) { 512 set_current_state(TASK_INTERRUPTIBLE); 513 514 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); 515 if (tbuf) 516 break; 517 518 if (tty_io_nonblock(tty, file)) { 519 error = -EAGAIN; 520 break; 521 } 522 schedule(); 523 524 if (signal_pending(current)) { 525 error = -EINTR; 526 break; 527 } 528 } 529 530 __set_current_state(TASK_RUNNING); 531 remove_wait_queue(&tty->write_wait, &wait); 532 533 if (!error) { 534 /* Retrieve the user's buffer */ 535 memcpy(tbuf->buf, data, count); 536 537 /* Send the data */ 538 tbuf->count = error = count; 539 n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf); 540 n_hdlc_send_frames(n_hdlc, tty); 541 } 542 543 return error; 544 545 } /* end of n_hdlc_tty_write() */ 546 547 /** 548 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device. 549 * @tty - pointer to tty instance data 550 * @file - pointer to open file object for device 551 * @cmd - IOCTL command code 552 * @arg - argument for IOCTL call (cmd dependent) 553 * 554 * Returns command dependent result. 555 */ 556 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, 557 unsigned int cmd, unsigned long arg) 558 { 559 struct n_hdlc *n_hdlc = tty->disc_data; 560 int error = 0; 561 int count; 562 unsigned long flags; 563 struct n_hdlc_buf *buf = NULL; 564 565 pr_debug("%s() called %d\n", __func__, cmd); 566 567 /* Verify the status of the device */ 568 if (n_hdlc->magic != HDLC_MAGIC) 569 return -EBADF; 570 571 switch (cmd) { 572 case FIONREAD: 573 /* report count of read data available */ 574 /* in next available frame (if any) */ 575 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags); 576 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list, 577 struct n_hdlc_buf, list_item); 578 if (buf) 579 count = buf->count; 580 else 581 count = 0; 582 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags); 583 error = put_user(count, (int __user *)arg); 584 break; 585 586 case TIOCOUTQ: 587 /* get the pending tx byte count in the driver */ 588 count = tty_chars_in_buffer(tty); 589 /* add size of next output frame in queue */ 590 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 591 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list, 592 struct n_hdlc_buf, list_item); 593 if (buf) 594 count += buf->count; 595 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 596 error = put_user(count, (int __user *)arg); 597 break; 598 599 case TCFLSH: 600 switch (arg) { 601 case TCIOFLUSH: 602 case TCOFLUSH: 603 flush_tx_queue(tty); 604 } 605 /* fall through - to default */ 606 607 default: 608 error = n_tty_ioctl_helper(tty, file, cmd, arg); 609 break; 610 } 611 return error; 612 613 } /* end of n_hdlc_tty_ioctl() */ 614 615 /** 616 * n_hdlc_tty_poll - TTY callback for poll system call 617 * @tty - pointer to tty instance data 618 * @filp - pointer to open file object for device 619 * @poll_table - wait queue for operations 620 * 621 * Determine which operations (read/write) will not block and return info 622 * to caller. 623 * Returns a bit mask containing info on which ops will not block. 624 */ 625 static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, 626 poll_table *wait) 627 { 628 struct n_hdlc *n_hdlc = tty->disc_data; 629 __poll_t mask = 0; 630 631 if (n_hdlc->magic != HDLC_MAGIC) 632 return 0; 633 634 /* 635 * queue the current process into any wait queue that may awaken in the 636 * future (read and write) 637 */ 638 poll_wait(filp, &tty->read_wait, wait); 639 poll_wait(filp, &tty->write_wait, wait); 640 641 /* set bits for operations that won't block */ 642 if (!list_empty(&n_hdlc->rx_buf_list.list)) 643 mask |= EPOLLIN | EPOLLRDNORM; /* readable */ 644 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) 645 mask |= EPOLLHUP; 646 if (tty_hung_up_p(filp)) 647 mask |= EPOLLHUP; 648 if (!tty_is_writelocked(tty) && 649 !list_empty(&n_hdlc->tx_free_buf_list.list)) 650 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */ 651 652 return mask; 653 } /* end of n_hdlc_tty_poll() */ 654 655 static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count, 656 const char *name) 657 { 658 struct n_hdlc_buf *buf; 659 unsigned int i; 660 661 for (i = 0; i < count; i++) { 662 buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL); 663 if (!buf) { 664 pr_debug("%s(), kmalloc() failed for %s buffer %u\n", 665 __func__, name, i); 666 return; 667 } 668 n_hdlc_buf_put(list, buf); 669 } 670 } 671 672 /** 673 * n_hdlc_alloc - allocate an n_hdlc instance data structure 674 * 675 * Returns a pointer to newly created structure if success, otherwise %NULL 676 */ 677 static struct n_hdlc *n_hdlc_alloc(void) 678 { 679 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL); 680 681 if (!n_hdlc) 682 return NULL; 683 684 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock); 685 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); 686 spin_lock_init(&n_hdlc->rx_buf_list.spinlock); 687 spin_lock_init(&n_hdlc->tx_buf_list.spinlock); 688 689 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list); 690 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list); 691 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list); 692 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list); 693 694 n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx"); 695 n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx"); 696 697 /* Initialize the control block */ 698 n_hdlc->magic = HDLC_MAGIC; 699 700 return n_hdlc; 701 702 } /* end of n_hdlc_alloc() */ 703 704 /** 705 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list 706 * @buf_list - pointer to the buffer list 707 * @buf - pointer to the buffer 708 */ 709 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, 710 struct n_hdlc_buf *buf) 711 { 712 unsigned long flags; 713 714 spin_lock_irqsave(&buf_list->spinlock, flags); 715 716 list_add(&buf->list_item, &buf_list->list); 717 buf_list->count++; 718 719 spin_unlock_irqrestore(&buf_list->spinlock, flags); 720 } 721 722 /** 723 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list 724 * @buf_list - pointer to buffer list 725 * @buf - pointer to buffer 726 */ 727 static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list, 728 struct n_hdlc_buf *buf) 729 { 730 unsigned long flags; 731 732 spin_lock_irqsave(&buf_list->spinlock, flags); 733 734 list_add_tail(&buf->list_item, &buf_list->list); 735 buf_list->count++; 736 737 spin_unlock_irqrestore(&buf_list->spinlock, flags); 738 } /* end of n_hdlc_buf_put() */ 739 740 /** 741 * n_hdlc_buf_get - remove and return an HDLC buffer from list 742 * @buf_list - pointer to HDLC buffer list 743 * 744 * Remove and return an HDLC buffer from the head of the specified HDLC buffer 745 * list. 746 * Returns a pointer to HDLC buffer if available, otherwise %NULL. 747 */ 748 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list) 749 { 750 unsigned long flags; 751 struct n_hdlc_buf *buf; 752 753 spin_lock_irqsave(&buf_list->spinlock, flags); 754 755 buf = list_first_entry_or_null(&buf_list->list, 756 struct n_hdlc_buf, list_item); 757 if (buf) { 758 list_del(&buf->list_item); 759 buf_list->count--; 760 } 761 762 spin_unlock_irqrestore(&buf_list->spinlock, flags); 763 return buf; 764 } /* end of n_hdlc_buf_get() */ 765 766 static struct tty_ldisc_ops n_hdlc_ldisc = { 767 .owner = THIS_MODULE, 768 .magic = TTY_LDISC_MAGIC, 769 .name = "hdlc", 770 .open = n_hdlc_tty_open, 771 .close = n_hdlc_tty_close, 772 .read = n_hdlc_tty_read, 773 .write = n_hdlc_tty_write, 774 .ioctl = n_hdlc_tty_ioctl, 775 .poll = n_hdlc_tty_poll, 776 .receive_buf = n_hdlc_tty_receive, 777 .write_wakeup = n_hdlc_tty_wakeup, 778 .flush_buffer = flush_rx_queue, 779 }; 780 781 static int __init n_hdlc_init(void) 782 { 783 int status; 784 785 /* range check maxframe arg */ 786 maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE); 787 788 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc); 789 if (!status) 790 pr_info("N_HDLC line discipline registered with maxframe=%d\n", 791 maxframe); 792 else 793 pr_err("N_HDLC: error registering line discipline: %d\n", 794 status); 795 796 return status; 797 798 } /* end of init_module() */ 799 800 static void __exit n_hdlc_exit(void) 801 { 802 /* Release tty registration of line discipline */ 803 int status = tty_unregister_ldisc(N_HDLC); 804 805 if (status) 806 pr_err("N_HDLC: can't unregister line discipline (err = %d)\n", 807 status); 808 else 809 pr_info("N_HDLC: line discipline unregistered\n"); 810 } 811 812 module_init(n_hdlc_init); 813 module_exit(n_hdlc_exit); 814 815 MODULE_LICENSE("GPL"); 816 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com"); 817 module_param(maxframe, int, 0); 818 MODULE_ALIAS_LDISC(N_HDLC); 819