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 #undef VERSION 91 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch)) 92 93 #include <linux/poll.h> 94 #include <linux/in.h> 95 #include <linux/ioctl.h> 96 #include <linux/slab.h> 97 #include <linux/tty.h> 98 #include <linux/errno.h> 99 #include <linux/string.h> /* used in new tty drivers */ 100 #include <linux/signal.h> /* used in new tty drivers */ 101 #include <linux/if.h> 102 #include <linux/bitops.h> 103 104 #include <asm/termios.h> 105 #include <linux/uaccess.h> 106 107 /* 108 * Buffers for individual HDLC frames 109 */ 110 #define MAX_HDLC_FRAME_SIZE 65535 111 #define DEFAULT_RX_BUF_COUNT 10 112 #define MAX_RX_BUF_COUNT 60 113 #define DEFAULT_TX_BUF_COUNT 3 114 115 struct n_hdlc_buf { 116 struct list_head list_item; 117 int count; 118 char buf[1]; 119 }; 120 121 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe) 122 123 struct n_hdlc_buf_list { 124 struct list_head list; 125 int count; 126 spinlock_t spinlock; 127 }; 128 129 /** 130 * struct n_hdlc - per device instance data structure 131 * @magic - magic value for structure 132 * @flags - miscellaneous control flags 133 * @tty - ptr to TTY structure 134 * @backup_tty - TTY to use if tty gets closed 135 * @tbusy - reentrancy flag for tx wakeup code 136 * @woke_up - FIXME: describe this field 137 * @tx_buf_list - list of pending transmit frame buffers 138 * @rx_buf_list - list of received frame buffers 139 * @tx_free_buf_list - list unused transmit frame buffers 140 * @rx_free_buf_list - list unused received frame buffers 141 */ 142 struct n_hdlc { 143 int magic; 144 __u32 flags; 145 struct tty_struct *tty; 146 struct tty_struct *backup_tty; 147 int tbusy; 148 int woke_up; 149 struct n_hdlc_buf_list tx_buf_list; 150 struct n_hdlc_buf_list rx_buf_list; 151 struct n_hdlc_buf_list tx_free_buf_list; 152 struct n_hdlc_buf_list rx_free_buf_list; 153 }; 154 155 /* 156 * HDLC buffer list manipulation functions 157 */ 158 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, 159 struct n_hdlc_buf *buf); 160 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, 161 struct n_hdlc_buf *buf); 162 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); 163 164 /* Local functions */ 165 166 static struct n_hdlc *n_hdlc_alloc (void); 167 168 /* debug level can be set by insmod for debugging purposes */ 169 #define DEBUG_LEVEL_INFO 1 170 static int debuglevel; 171 172 /* max frame size for memory allocations */ 173 static int maxframe = 4096; 174 175 /* TTY callbacks */ 176 177 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, 178 __u8 __user *buf, size_t nr); 179 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, 180 const unsigned char *buf, size_t nr); 181 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, 182 unsigned int cmd, unsigned long arg); 183 static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, 184 poll_table *wait); 185 static int n_hdlc_tty_open(struct tty_struct *tty); 186 static void n_hdlc_tty_close(struct tty_struct *tty); 187 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp, 188 char *fp, int count); 189 static void n_hdlc_tty_wakeup(struct tty_struct *tty); 190 191 #define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f))) 192 193 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data)) 194 #define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty) 195 196 static void flush_rx_queue(struct tty_struct *tty) 197 { 198 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 199 struct n_hdlc_buf *buf; 200 201 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list))) 202 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf); 203 } 204 205 static void flush_tx_queue(struct tty_struct *tty) 206 { 207 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 208 struct n_hdlc_buf *buf; 209 210 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) 211 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); 212 } 213 214 static struct tty_ldisc_ops n_hdlc_ldisc = { 215 .owner = THIS_MODULE, 216 .magic = TTY_LDISC_MAGIC, 217 .name = "hdlc", 218 .open = n_hdlc_tty_open, 219 .close = n_hdlc_tty_close, 220 .read = n_hdlc_tty_read, 221 .write = n_hdlc_tty_write, 222 .ioctl = n_hdlc_tty_ioctl, 223 .poll = n_hdlc_tty_poll, 224 .receive_buf = n_hdlc_tty_receive, 225 .write_wakeup = n_hdlc_tty_wakeup, 226 .flush_buffer = flush_rx_queue, 227 }; 228 229 /** 230 * n_hdlc_release - release an n_hdlc per device line discipline info structure 231 * @n_hdlc - per device line discipline info structure 232 */ 233 static void n_hdlc_release(struct n_hdlc *n_hdlc) 234 { 235 struct tty_struct *tty = n_hdlc2tty (n_hdlc); 236 struct n_hdlc_buf *buf; 237 238 if (debuglevel >= DEBUG_LEVEL_INFO) 239 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__); 240 241 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */ 242 wake_up_interruptible (&tty->read_wait); 243 wake_up_interruptible (&tty->write_wait); 244 245 if (tty->disc_data == n_hdlc) 246 tty->disc_data = NULL; /* Break the tty->n_hdlc link */ 247 248 /* Release transmit and receive buffers */ 249 for(;;) { 250 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); 251 if (buf) { 252 kfree(buf); 253 } else 254 break; 255 } 256 for(;;) { 257 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); 258 if (buf) { 259 kfree(buf); 260 } else 261 break; 262 } 263 for(;;) { 264 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); 265 if (buf) { 266 kfree(buf); 267 } else 268 break; 269 } 270 for(;;) { 271 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 272 if (buf) { 273 kfree(buf); 274 } else 275 break; 276 } 277 kfree(n_hdlc); 278 279 } /* end of n_hdlc_release() */ 280 281 /** 282 * n_hdlc_tty_close - line discipline close 283 * @tty - pointer to tty info structure 284 * 285 * Called when the line discipline is changed to something 286 * else, the tty is closed, or the tty detects a hangup. 287 */ 288 static void n_hdlc_tty_close(struct tty_struct *tty) 289 { 290 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 291 292 if (debuglevel >= DEBUG_LEVEL_INFO) 293 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__); 294 295 if (n_hdlc != NULL) { 296 if (n_hdlc->magic != HDLC_MAGIC) { 297 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n"); 298 return; 299 } 300 #if defined(TTY_NO_WRITE_SPLIT) 301 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags); 302 #endif 303 tty->disc_data = NULL; 304 if (tty == n_hdlc->backup_tty) 305 n_hdlc->backup_tty = NULL; 306 if (tty != n_hdlc->tty) 307 return; 308 if (n_hdlc->backup_tty) { 309 n_hdlc->tty = n_hdlc->backup_tty; 310 } else { 311 n_hdlc_release (n_hdlc); 312 } 313 } 314 315 if (debuglevel >= DEBUG_LEVEL_INFO) 316 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__); 317 318 } /* end of n_hdlc_tty_close() */ 319 320 /** 321 * n_hdlc_tty_open - called when line discipline changed to n_hdlc 322 * @tty - pointer to tty info structure 323 * 324 * Returns 0 if success, otherwise error code 325 */ 326 static int n_hdlc_tty_open (struct tty_struct *tty) 327 { 328 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 329 330 if (debuglevel >= DEBUG_LEVEL_INFO) 331 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n", 332 __FILE__,__LINE__, 333 tty->name); 334 335 /* There should not be an existing table for this slot. */ 336 if (n_hdlc) { 337 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" ); 338 return -EEXIST; 339 } 340 341 n_hdlc = n_hdlc_alloc(); 342 if (!n_hdlc) { 343 printk (KERN_ERR "n_hdlc_alloc failed\n"); 344 return -ENFILE; 345 } 346 347 tty->disc_data = n_hdlc; 348 n_hdlc->tty = tty; 349 tty->receive_room = 65536; 350 351 #if defined(TTY_NO_WRITE_SPLIT) 352 /* change tty_io write() to not split large writes into 8K chunks */ 353 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags); 354 #endif 355 356 /* flush receive data from driver */ 357 tty_driver_flush_buffer(tty); 358 359 if (debuglevel >= DEBUG_LEVEL_INFO) 360 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__); 361 362 return 0; 363 364 } /* end of n_tty_hdlc_open() */ 365 366 /** 367 * n_hdlc_send_frames - send frames on pending send buffer list 368 * @n_hdlc - pointer to ldisc instance data 369 * @tty - pointer to tty instance data 370 * 371 * Send frames on pending send buffer list until the driver does not accept a 372 * frame (busy) this function is called after adding a frame to the send buffer 373 * list and by the tty wakeup callback. 374 */ 375 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) 376 { 377 register int actual; 378 unsigned long flags; 379 struct n_hdlc_buf *tbuf; 380 381 if (debuglevel >= DEBUG_LEVEL_INFO) 382 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__); 383 check_again: 384 385 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 386 if (n_hdlc->tbusy) { 387 n_hdlc->woke_up = 1; 388 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 389 return; 390 } 391 n_hdlc->tbusy = 1; 392 n_hdlc->woke_up = 0; 393 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 394 395 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 396 while (tbuf) { 397 if (debuglevel >= DEBUG_LEVEL_INFO) 398 printk("%s(%d)sending frame %p, count=%d\n", 399 __FILE__,__LINE__,tbuf,tbuf->count); 400 401 /* Send the next block of data to device */ 402 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 403 actual = tty->ops->write(tty, tbuf->buf, tbuf->count); 404 405 /* rollback was possible and has been done */ 406 if (actual == -ERESTARTSYS) { 407 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); 408 break; 409 } 410 /* if transmit error, throw frame away by */ 411 /* pretending it was accepted by driver */ 412 if (actual < 0) 413 actual = tbuf->count; 414 415 if (actual == tbuf->count) { 416 if (debuglevel >= DEBUG_LEVEL_INFO) 417 printk("%s(%d)frame %p completed\n", 418 __FILE__,__LINE__,tbuf); 419 420 /* free current transmit buffer */ 421 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf); 422 423 /* wait up sleeping writers */ 424 wake_up_interruptible(&tty->write_wait); 425 426 /* get next pending transmit buffer */ 427 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); 428 } else { 429 if (debuglevel >= DEBUG_LEVEL_INFO) 430 printk("%s(%d)frame %p pending\n", 431 __FILE__,__LINE__,tbuf); 432 433 /* 434 * the buffer was not accepted by driver, 435 * return it back into tx queue 436 */ 437 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); 438 break; 439 } 440 } 441 442 if (!tbuf) 443 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 444 445 /* Clear the re-entry flag */ 446 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); 447 n_hdlc->tbusy = 0; 448 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 449 450 if (n_hdlc->woke_up) 451 goto check_again; 452 453 if (debuglevel >= DEBUG_LEVEL_INFO) 454 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__); 455 456 } /* end of n_hdlc_send_frames() */ 457 458 /** 459 * n_hdlc_tty_wakeup - Callback for transmit wakeup 460 * @tty - pointer to associated tty instance data 461 * 462 * Called when low level device driver can accept more send data. 463 */ 464 static void n_hdlc_tty_wakeup(struct tty_struct *tty) 465 { 466 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 467 468 if (debuglevel >= DEBUG_LEVEL_INFO) 469 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__); 470 471 if (!n_hdlc) 472 return; 473 474 if (tty != n_hdlc->tty) { 475 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 476 return; 477 } 478 479 n_hdlc_send_frames (n_hdlc, tty); 480 481 } /* end of n_hdlc_tty_wakeup() */ 482 483 /** 484 * n_hdlc_tty_receive - Called by tty driver when receive data is available 485 * @tty - pointer to tty instance data 486 * @data - pointer to received data 487 * @flags - pointer to flags for data 488 * @count - count of received data in bytes 489 * 490 * Called by tty low level driver when receive data is available. Data is 491 * interpreted as one HDLC frame. 492 */ 493 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data, 494 char *flags, int count) 495 { 496 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 497 register struct n_hdlc_buf *buf; 498 499 if (debuglevel >= DEBUG_LEVEL_INFO) 500 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n", 501 __FILE__,__LINE__, count); 502 503 /* This can happen if stuff comes in on the backup tty */ 504 if (!n_hdlc || tty != n_hdlc->tty) 505 return; 506 507 /* verify line is using HDLC discipline */ 508 if (n_hdlc->magic != HDLC_MAGIC) { 509 printk("%s(%d) line not using HDLC discipline\n", 510 __FILE__,__LINE__); 511 return; 512 } 513 514 if ( count>maxframe ) { 515 if (debuglevel >= DEBUG_LEVEL_INFO) 516 printk("%s(%d) rx count>maxframesize, data discarded\n", 517 __FILE__,__LINE__); 518 return; 519 } 520 521 /* get a free HDLC buffer */ 522 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list); 523 if (!buf) { 524 /* no buffers in free list, attempt to allocate another rx buffer */ 525 /* unless the maximum count has been reached */ 526 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT) 527 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC); 528 } 529 530 if (!buf) { 531 if (debuglevel >= DEBUG_LEVEL_INFO) 532 printk("%s(%d) no more rx buffers, data discarded\n", 533 __FILE__,__LINE__); 534 return; 535 } 536 537 /* copy received data to HDLC buffer */ 538 memcpy(buf->buf,data,count); 539 buf->count=count; 540 541 /* add HDLC buffer to list of received frames */ 542 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf); 543 544 /* wake up any blocked reads and perform async signalling */ 545 wake_up_interruptible (&tty->read_wait); 546 if (n_hdlc->tty->fasync != NULL) 547 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN); 548 549 } /* end of n_hdlc_tty_receive() */ 550 551 /** 552 * n_hdlc_tty_read - Called to retrieve one frame of data (if available) 553 * @tty - pointer to tty instance data 554 * @file - pointer to open file object 555 * @buf - pointer to returned data buffer 556 * @nr - size of returned data buffer 557 * 558 * Returns the number of bytes returned or error code. 559 */ 560 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, 561 __u8 __user *buf, size_t nr) 562 { 563 struct n_hdlc *n_hdlc = tty2n_hdlc(tty); 564 int ret = 0; 565 struct n_hdlc_buf *rbuf; 566 DECLARE_WAITQUEUE(wait, current); 567 568 if (debuglevel >= DEBUG_LEVEL_INFO) 569 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__); 570 571 /* Validate the pointers */ 572 if (!n_hdlc) 573 return -EIO; 574 575 /* verify user access to buffer */ 576 if (!access_ok(buf, nr)) { 577 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user " 578 "buffer\n", __FILE__, __LINE__); 579 return -EFAULT; 580 } 581 582 add_wait_queue(&tty->read_wait, &wait); 583 584 for (;;) { 585 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { 586 ret = -EIO; 587 break; 588 } 589 if (tty_hung_up_p(file)) 590 break; 591 592 set_current_state(TASK_INTERRUPTIBLE); 593 594 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list); 595 if (rbuf) { 596 if (rbuf->count > nr) { 597 /* too large for caller's buffer */ 598 ret = -EOVERFLOW; 599 } else { 600 __set_current_state(TASK_RUNNING); 601 if (copy_to_user(buf, rbuf->buf, rbuf->count)) 602 ret = -EFAULT; 603 else 604 ret = rbuf->count; 605 } 606 607 if (n_hdlc->rx_free_buf_list.count > 608 DEFAULT_RX_BUF_COUNT) 609 kfree(rbuf); 610 else 611 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf); 612 break; 613 } 614 615 /* no data */ 616 if (tty_io_nonblock(tty, file)) { 617 ret = -EAGAIN; 618 break; 619 } 620 621 schedule(); 622 623 if (signal_pending(current)) { 624 ret = -EINTR; 625 break; 626 } 627 } 628 629 remove_wait_queue(&tty->read_wait, &wait); 630 __set_current_state(TASK_RUNNING); 631 632 return ret; 633 634 } /* end of n_hdlc_tty_read() */ 635 636 /** 637 * n_hdlc_tty_write - write a single frame of data to device 638 * @tty - pointer to associated tty device instance data 639 * @file - pointer to file object data 640 * @data - pointer to transmit data (one frame) 641 * @count - size of transmit frame in bytes 642 * 643 * Returns the number of bytes written (or error code). 644 */ 645 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file, 646 const unsigned char *data, size_t count) 647 { 648 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 649 int error = 0; 650 DECLARE_WAITQUEUE(wait, current); 651 struct n_hdlc_buf *tbuf; 652 653 if (debuglevel >= DEBUG_LEVEL_INFO) 654 printk("%s(%d)n_hdlc_tty_write() called count=%zd\n", 655 __FILE__,__LINE__,count); 656 657 /* Verify pointers */ 658 if (!n_hdlc) 659 return -EIO; 660 661 if (n_hdlc->magic != HDLC_MAGIC) 662 return -EIO; 663 664 /* verify frame size */ 665 if (count > maxframe ) { 666 if (debuglevel & DEBUG_LEVEL_INFO) 667 printk (KERN_WARNING 668 "n_hdlc_tty_write: truncating user packet " 669 "from %lu to %d\n", (unsigned long) count, 670 maxframe ); 671 count = maxframe; 672 } 673 674 add_wait_queue(&tty->write_wait, &wait); 675 676 for (;;) { 677 set_current_state(TASK_INTERRUPTIBLE); 678 679 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list); 680 if (tbuf) 681 break; 682 683 if (tty_io_nonblock(tty, file)) { 684 error = -EAGAIN; 685 break; 686 } 687 schedule(); 688 689 n_hdlc = tty2n_hdlc (tty); 690 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 691 tty != n_hdlc->tty) { 692 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc); 693 error = -EIO; 694 break; 695 } 696 697 if (signal_pending(current)) { 698 error = -EINTR; 699 break; 700 } 701 } 702 703 __set_current_state(TASK_RUNNING); 704 remove_wait_queue(&tty->write_wait, &wait); 705 706 if (!error) { 707 /* Retrieve the user's buffer */ 708 memcpy(tbuf->buf, data, count); 709 710 /* Send the data */ 711 tbuf->count = error = count; 712 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf); 713 n_hdlc_send_frames(n_hdlc,tty); 714 } 715 716 return error; 717 718 } /* end of n_hdlc_tty_write() */ 719 720 /** 721 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device. 722 * @tty - pointer to tty instance data 723 * @file - pointer to open file object for device 724 * @cmd - IOCTL command code 725 * @arg - argument for IOCTL call (cmd dependent) 726 * 727 * Returns command dependent result. 728 */ 729 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, 730 unsigned int cmd, unsigned long arg) 731 { 732 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 733 int error = 0; 734 int count; 735 unsigned long flags; 736 struct n_hdlc_buf *buf = NULL; 737 738 if (debuglevel >= DEBUG_LEVEL_INFO) 739 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n", 740 __FILE__,__LINE__,cmd); 741 742 /* Verify the status of the device */ 743 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC) 744 return -EBADF; 745 746 switch (cmd) { 747 case FIONREAD: 748 /* report count of read data available */ 749 /* in next available frame (if any) */ 750 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags); 751 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list, 752 struct n_hdlc_buf, list_item); 753 if (buf) 754 count = buf->count; 755 else 756 count = 0; 757 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags); 758 error = put_user(count, (int __user *)arg); 759 break; 760 761 case TIOCOUTQ: 762 /* get the pending tx byte count in the driver */ 763 count = tty_chars_in_buffer(tty); 764 /* add size of next output frame in queue */ 765 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags); 766 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list, 767 struct n_hdlc_buf, list_item); 768 if (buf) 769 count += buf->count; 770 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags); 771 error = put_user(count, (int __user *)arg); 772 break; 773 774 case TCFLSH: 775 switch (arg) { 776 case TCIOFLUSH: 777 case TCOFLUSH: 778 flush_tx_queue(tty); 779 } 780 /* fall through - to default */ 781 782 default: 783 error = n_tty_ioctl_helper(tty, file, cmd, arg); 784 break; 785 } 786 return error; 787 788 } /* end of n_hdlc_tty_ioctl() */ 789 790 /** 791 * n_hdlc_tty_poll - TTY callback for poll system call 792 * @tty - pointer to tty instance data 793 * @filp - pointer to open file object for device 794 * @poll_table - wait queue for operations 795 * 796 * Determine which operations (read/write) will not block and return info 797 * to caller. 798 * Returns a bit mask containing info on which ops will not block. 799 */ 800 static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, 801 poll_table *wait) 802 { 803 struct n_hdlc *n_hdlc = tty2n_hdlc (tty); 804 __poll_t mask = 0; 805 806 if (debuglevel >= DEBUG_LEVEL_INFO) 807 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__); 808 809 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) { 810 /* queue current process into any wait queue that */ 811 /* may awaken in the future (read and write) */ 812 813 poll_wait(filp, &tty->read_wait, wait); 814 poll_wait(filp, &tty->write_wait, wait); 815 816 /* set bits for operations that won't block */ 817 if (!list_empty(&n_hdlc->rx_buf_list.list)) 818 mask |= EPOLLIN | EPOLLRDNORM; /* readable */ 819 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) 820 mask |= EPOLLHUP; 821 if (tty_hung_up_p(filp)) 822 mask |= EPOLLHUP; 823 if (!tty_is_writelocked(tty) && 824 !list_empty(&n_hdlc->tx_free_buf_list.list)) 825 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */ 826 } 827 return mask; 828 } /* end of n_hdlc_tty_poll() */ 829 830 /** 831 * n_hdlc_alloc - allocate an n_hdlc instance data structure 832 * 833 * Returns a pointer to newly created structure if success, otherwise %NULL 834 */ 835 static struct n_hdlc *n_hdlc_alloc(void) 836 { 837 struct n_hdlc_buf *buf; 838 int i; 839 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL); 840 841 if (!n_hdlc) 842 return NULL; 843 844 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock); 845 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); 846 spin_lock_init(&n_hdlc->rx_buf_list.spinlock); 847 spin_lock_init(&n_hdlc->tx_buf_list.spinlock); 848 849 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list); 850 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list); 851 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list); 852 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list); 853 854 /* allocate free rx buffer list */ 855 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) { 856 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL); 857 if (buf) 858 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf); 859 else if (debuglevel >= DEBUG_LEVEL_INFO) 860 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i); 861 } 862 863 /* allocate free tx buffer list */ 864 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) { 865 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL); 866 if (buf) 867 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf); 868 else if (debuglevel >= DEBUG_LEVEL_INFO) 869 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i); 870 } 871 872 /* Initialize the control block */ 873 n_hdlc->magic = HDLC_MAGIC; 874 n_hdlc->flags = 0; 875 876 return n_hdlc; 877 878 } /* end of n_hdlc_alloc() */ 879 880 /** 881 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list 882 * @buf_list - pointer to the buffer list 883 * @buf - pointer to the buffer 884 */ 885 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, 886 struct n_hdlc_buf *buf) 887 { 888 unsigned long flags; 889 890 spin_lock_irqsave(&buf_list->spinlock, flags); 891 892 list_add(&buf->list_item, &buf_list->list); 893 buf_list->count++; 894 895 spin_unlock_irqrestore(&buf_list->spinlock, flags); 896 } 897 898 /** 899 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list 900 * @buf_list - pointer to buffer list 901 * @buf - pointer to buffer 902 */ 903 static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list, 904 struct n_hdlc_buf *buf) 905 { 906 unsigned long flags; 907 908 spin_lock_irqsave(&buf_list->spinlock, flags); 909 910 list_add_tail(&buf->list_item, &buf_list->list); 911 buf_list->count++; 912 913 spin_unlock_irqrestore(&buf_list->spinlock, flags); 914 } /* end of n_hdlc_buf_put() */ 915 916 /** 917 * n_hdlc_buf_get - remove and return an HDLC buffer from list 918 * @buf_list - pointer to HDLC buffer list 919 * 920 * Remove and return an HDLC buffer from the head of the specified HDLC buffer 921 * list. 922 * Returns a pointer to HDLC buffer if available, otherwise %NULL. 923 */ 924 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list) 925 { 926 unsigned long flags; 927 struct n_hdlc_buf *buf; 928 929 spin_lock_irqsave(&buf_list->spinlock, flags); 930 931 buf = list_first_entry_or_null(&buf_list->list, 932 struct n_hdlc_buf, list_item); 933 if (buf) { 934 list_del(&buf->list_item); 935 buf_list->count--; 936 } 937 938 spin_unlock_irqrestore(&buf_list->spinlock, flags); 939 return buf; 940 } /* end of n_hdlc_buf_get() */ 941 942 static const char hdlc_banner[] __initconst = 943 KERN_INFO "HDLC line discipline maxframe=%u\n"; 944 static const char hdlc_register_ok[] __initconst = 945 KERN_INFO "N_HDLC line discipline registered.\n"; 946 static const char hdlc_register_fail[] __initconst = 947 KERN_ERR "error registering line discipline: %d\n"; 948 949 static int __init n_hdlc_init(void) 950 { 951 int status; 952 953 /* range check maxframe arg */ 954 if (maxframe < 4096) 955 maxframe = 4096; 956 else if (maxframe > 65535) 957 maxframe = 65535; 958 959 printk(hdlc_banner, maxframe); 960 961 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc); 962 if (!status) 963 printk(hdlc_register_ok); 964 else 965 printk(hdlc_register_fail, status); 966 967 return status; 968 969 } /* end of init_module() */ 970 971 #ifdef CONFIG_SPARC 972 #undef __exitdata 973 #define __exitdata 974 #endif 975 976 static const char hdlc_unregister_ok[] __exitdata = 977 KERN_INFO "N_HDLC: line discipline unregistered\n"; 978 static const char hdlc_unregister_fail[] __exitdata = 979 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n"; 980 981 static void __exit n_hdlc_exit(void) 982 { 983 /* Release tty registration of line discipline */ 984 int status = tty_unregister_ldisc(N_HDLC); 985 986 if (status) 987 printk(hdlc_unregister_fail, status); 988 else 989 printk(hdlc_unregister_ok); 990 } 991 992 module_init(n_hdlc_init); 993 module_exit(n_hdlc_exit); 994 995 MODULE_LICENSE("GPL"); 996 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com"); 997 module_param(debuglevel, int, 0); 998 module_param(maxframe, int, 0); 999 MODULE_ALIAS_LDISC(N_HDLC); 1000