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