git.oblomov.eu Git - linux-2.6/blob - drivers/char/n_hdlc.c

   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  * $Id: n_hdlc.c,v 4.8 2003/05/06 21:18:51 paulkf Exp $
  14  *
  15  * This code is released under the GNU General Public License (GPL)
  16  *
  17  * This module implements the tty line discipline N_HDLC for use with
  18  * tty device drivers that support bit-synchronous HDLC communications.
  19  *
  20  * All HDLC data is frame oriented which means:
  21  *
  22  * 1. tty write calls represent one complete transmit frame of data
  23  *    The device driver should accept the complete frame or none of
  24  *    the frame (busy) in the write method. Each write call should have
  25  *    a byte count in the range of 2-65535 bytes (2 is min HDLC frame
  26  *    with 1 addr byte and 1 ctrl byte). The max byte count of 65535
  27  *    should include any crc bytes required. For example, when using
  28  *    CCITT CRC32, 4 crc bytes are required, so the maximum size frame
  29  *    the application may transmit is limited to 65531 bytes. For CCITT
  30  *    CRC16, the maximum application frame size would be 65533.
  31  *
  32  *
  33  * 2. receive callbacks from the device driver represents
  34  *    one received frame. The device driver should bypass
  35  *    the tty flip buffer and call the line discipline receive
  36  *    callback directly to avoid fragmenting or concatenating
  37  *    multiple frames into a single receive callback.
  38  *
  39  *    The HDLC line discipline queues the receive frames in separate
  40  *    buffers so complete receive frames can be returned by the
  41  *    tty read calls.
  42  *
  43  * 3. tty read calls returns an entire frame of data or nothing.
  44  *
  45  * 4. all send and receive data is considered raw. No processing
  46  *    or translation is performed by the line discipline, regardless
  47  *    of the tty flags
  48  *
  49  * 5. When line discipline is queried for the amount of receive
  50  *    data available (FIOC), 0 is returned if no data available,
  51  *    otherwise the count of the next available frame is returned.
  52  *    (instead of the sum of all received frame counts).
  53  *
  54  * These conventions allow the standard tty programming interface
  55  * to be used for synchronous HDLC applications when used with
  56  * this line discipline (or another line discipline that is frame
  57  * oriented such as N_PPP).
  58  *
  59  * The SyncLink driver (synclink.c) implements both asynchronous
  60  * (using standard line discipline N_TTY) and synchronous HDLC
  61  * (using N_HDLC) communications, with the latter using the above
  62  * conventions.
  63  *
  64  * This implementation is very basic and does not maintain
  65  * any statistics. The main point is to enforce the raw data
  66  * and frame orientation of HDLC communications.
  67  *
  68  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  69  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  70  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  71  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  72  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  73  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  74  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  75  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  76  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  77  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  78  * OF THE POSSIBILITY OF SUCH DAMAGE.
  79  */
  80
  81 #define HDLC_MAGIC 0x239e
  82 #define HDLC_VERSION "$Revision: 4.8 $"
  83
  84 #include <linux/config.h>
  85 #include <linux/module.h>
  86 #include <linux/init.h>
  87 #include <linux/kernel.h>
  88 #include <linux/sched.h>
  89 #include <linux/types.h>
  90 #include <linux/fcntl.h>
  91 #include <linux/interrupt.h>
  92 #include <linux/ptrace.h>
  93
  94 #undef VERSION
  95 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
  96
  97 #include <linux/poll.h>
  98 #include <linux/in.h>
  99 #include <linux/ioctl.h>
 100 #include <linux/slab.h>
 101 #include <linux/tty.h>
 102 #include <linux/errno.h>
 103 #include <linux/string.h>       /* used in new tty drivers */
 104 #include <linux/signal.h>       /* used in new tty drivers */
 105 #include <linux/if.h>
 106 #include <linux/bitops.h>
 107
 108 #include <asm/system.h>
 109 #include <asm/termios.h>
 110 #include <asm/uaccess.h>
 111
 112 /*
 113  * Buffers for individual HDLC frames
 114  */
 115 #define MAX_HDLC_FRAME_SIZE 65535
 116 #define DEFAULT_RX_BUF_COUNT 10
 117 #define MAX_RX_BUF_COUNT 60
 118 #define DEFAULT_TX_BUF_COUNT 1
 119
 120 struct n_hdlc_buf {
 121         struct n_hdlc_buf *link;
 122         int               count;
 123         char              buf[1];
 124 };
 125
 126 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
 127
 128 struct n_hdlc_buf_list {
 129         struct n_hdlc_buf *head;
 130         struct n_hdlc_buf *tail;
 131         int               count;
 132         spinlock_t        spinlock;
 133 };
 134
 135 /**
 136  * struct n_hdlc - per device instance data structure
 137  * @magic - magic value for structure
 138  * @flags - miscellaneous control flags
 139  * @tty - ptr to TTY structure
 140  * @backup_tty - TTY to use if tty gets closed
 141  * @tbusy - reentrancy flag for tx wakeup code
 142  * @woke_up - FIXME: describe this field
 143  * @tbuf - currently transmitting tx buffer
 144  * @tx_buf_list - list of pending transmit frame buffers
 145  * @rx_buf_list - list of received frame buffers
 146  * @tx_free_buf_list - list unused transmit frame buffers
 147  * @rx_free_buf_list - list unused received frame buffers
 148  */
 149 struct n_hdlc {
 150         int                     magic;
 151         __u32                   flags;
 152         struct tty_struct       *tty;
 153         struct tty_struct       *backup_tty;
 154         int                     tbusy;
 155         int                     woke_up;
 156         struct n_hdlc_buf       *tbuf;
 157         struct n_hdlc_buf_list  tx_buf_list;
 158         struct n_hdlc_buf_list  rx_buf_list;
 159         struct n_hdlc_buf_list  tx_free_buf_list;
 160         struct n_hdlc_buf_list  rx_free_buf_list;
 161 };
 162
 163 /*
 164  * HDLC buffer list manipulation functions
 165  */
 166 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
 167 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 168                            struct n_hdlc_buf *buf);
 169 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
 170
 171 /* Local functions */
 172
 173 static struct n_hdlc *n_hdlc_alloc (void);
 174
 175 /* debug level can be set by insmod for debugging purposes */
 176 #define DEBUG_LEVEL_INFO        1
 177 static int debuglevel;
 178
 179 /* max frame size for memory allocations */
 180 static int maxframe = 4096;
 181
 182 /* TTY callbacks */
 183
 184 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 185                            __u8 __user *buf, size_t nr);
 186 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 187                             const unsigned char *buf, size_t nr);
 188 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 189                             unsigned int cmd, unsigned long arg);
 190 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 191                                     poll_table *wait);
 192 static int n_hdlc_tty_open(struct tty_struct *tty);
 193 static void n_hdlc_tty_close(struct tty_struct *tty);
 194 static int n_hdlc_tty_room(struct tty_struct *tty);
 195 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
 196                                char *fp, int count);
 197 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
 198
 199 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
 200
 201 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
 202 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
 203
 204 static struct tty_ldisc n_hdlc_ldisc = {
 205         .owner          = THIS_MODULE,
 206         .magic          = TTY_LDISC_MAGIC,
 207         .name           = "hdlc",
 208         .open           = n_hdlc_tty_open,
 209         .close          = n_hdlc_tty_close,
 210         .read           = n_hdlc_tty_read,
 211         .write          = n_hdlc_tty_write,
 212         .ioctl          = n_hdlc_tty_ioctl,
 213         .poll           = n_hdlc_tty_poll,
 214         .receive_buf    = n_hdlc_tty_receive,
 215         .receive_room   = n_hdlc_tty_room,
 216         .write_wakeup   = n_hdlc_tty_wakeup,
 217 };
 218
 219 /**
 220  * n_hdlc_release - release an n_hdlc per device line discipline info structure
 221  * @n_hdlc - per device line discipline info structure
 222  */
 223 static void n_hdlc_release(struct n_hdlc *n_hdlc)
 224 {
 225         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
 226         struct n_hdlc_buf *buf;
 227
 228         if (debuglevel >= DEBUG_LEVEL_INFO)
 229                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
 230
 231         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
 232         wake_up_interruptible (&tty->read_wait);
 233         wake_up_interruptible (&tty->write_wait);
 234
 235         if (tty != NULL && tty->disc_data == n_hdlc)
 236                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
 237
 238         /* Release transmit and receive buffers */
 239         for(;;) {
 240                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 241                 if (buf) {
 242                         kfree(buf);
 243                 } else
 244                         break;
 245         }
 246         for(;;) {
 247                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
 248                 if (buf) {
 249                         kfree(buf);
 250                 } else
 251                         break;
 252         }
 253         for(;;) {
 254                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 255                 if (buf) {
 256                         kfree(buf);
 257                 } else
 258                         break;
 259         }
 260         for(;;) {
 261                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 262                 if (buf) {
 263                         kfree(buf);
 264                 } else
 265                         break;
 266         }
 267         if (n_hdlc->tbuf)
 268                 kfree(n_hdlc->tbuf);
 269         kfree(n_hdlc);
 270
 271 }       /* end of n_hdlc_release() */
 272
 273 /**
 274  * n_hdlc_tty_close - line discipline close
 275  * @tty - pointer to tty info structure
 276  *
 277  * Called when the line discipline is changed to something
 278  * else, the tty is closed, or the tty detects a hangup.
 279  */
 280 static void n_hdlc_tty_close(struct tty_struct *tty)
 281 {
 282         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 283
 284         if (debuglevel >= DEBUG_LEVEL_INFO)
 285                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
 286
 287         if (n_hdlc != NULL) {
 288                 if (n_hdlc->magic != HDLC_MAGIC) {
 289                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
 290                         return;
 291                 }
 292 #if defined(TTY_NO_WRITE_SPLIT)
 293                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 294 #endif
 295                 tty->disc_data = NULL;
 296                 if (tty == n_hdlc->backup_tty)
 297                         n_hdlc->backup_tty = NULL;
 298                 if (tty != n_hdlc->tty)
 299                         return;
 300                 if (n_hdlc->backup_tty) {
 301                         n_hdlc->tty = n_hdlc->backup_tty;
 302                 } else {
 303                         n_hdlc_release (n_hdlc);
 304                 }
 305         }
 306
 307         if (debuglevel >= DEBUG_LEVEL_INFO)
 308                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
 309
 310 }       /* end of n_hdlc_tty_close() */
 311
 312 /**
 313  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
 314  * @tty - pointer to tty info structure
 315  *
 316  * Returns 0 if success, otherwise error code
 317  */
 318 static int n_hdlc_tty_open (struct tty_struct *tty)
 319 {
 320         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 321
 322         if (debuglevel >= DEBUG_LEVEL_INFO)
 323                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
 324                 __FILE__,__LINE__,
 325                 tty->name);
 326
 327         /* There should not be an existing table for this slot. */
 328         if (n_hdlc) {
 329                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
 330                 return -EEXIST;
 331         }
 332
 333         n_hdlc = n_hdlc_alloc();
 334         if (!n_hdlc) {
 335                 printk (KERN_ERR "n_hdlc_alloc failed\n");
 336                 return -ENFILE;
 337         }
 338
 339         tty->disc_data = n_hdlc;
 340         n_hdlc->tty    = tty;
 341
 342 #if defined(TTY_NO_WRITE_SPLIT)
 343         /* change tty_io write() to not split large writes into 8K chunks */
 344         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 345 #endif
 346
 347         /* Flush any pending characters in the driver and discipline. */
 348
 349         if (tty->ldisc.flush_buffer)
 350                 tty->ldisc.flush_buffer (tty);
 351
 352         if (tty->driver->flush_buffer)
 353                 tty->driver->flush_buffer (tty);
 354
 355         if (debuglevel >= DEBUG_LEVEL_INFO)
 356                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
 357
 358         return 0;
 359
 360 }       /* end of n_tty_hdlc_open() */
 361
 362 /**
 363  * n_hdlc_send_frames - send frames on pending send buffer list
 364  * @n_hdlc - pointer to ldisc instance data
 365  * @tty - pointer to tty instance data
 366  *
 367  * Send frames on pending send buffer list until the driver does not accept a
 368  * frame (busy) this function is called after adding a frame to the send buffer
 369  * list and by the tty wakeup callback.
 370  */
 371 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 372 {
 373         register int actual;
 374         unsigned long flags;
 375         struct n_hdlc_buf *tbuf;
 376
 377         if (debuglevel >= DEBUG_LEVEL_INFO)
 378                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
 379  check_again:
 380
 381         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 382         if (n_hdlc->tbusy) {
 383                 n_hdlc->woke_up = 1;
 384                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 385                 return;
 386         }
 387         n_hdlc->tbusy = 1;
 388         n_hdlc->woke_up = 0;
 389         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 390
 391         /* get current transmit buffer or get new transmit */
 392         /* buffer from list of pending transmit buffers */
 393
 394         tbuf = n_hdlc->tbuf;
 395         if (!tbuf)
 396                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 397
 398         while (tbuf) {
 399                 if (debuglevel >= DEBUG_LEVEL_INFO)
 400                         printk("%s(%d)sending frame %p, count=%d\n",
 401                                 __FILE__,__LINE__,tbuf,tbuf->count);
 402
 403                 /* Send the next block of data to device */
 404                 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
 405                 actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
 406
 407                 /* if transmit error, throw frame away by */
 408                 /* pretending it was accepted by driver */
 409                 if (actual < 0)
 410                         actual = tbuf->count;
 411
 412                 if (actual == tbuf->count) {
 413                         if (debuglevel >= DEBUG_LEVEL_INFO)
 414                                 printk("%s(%d)frame %p completed\n",
 415                                         __FILE__,__LINE__,tbuf);
 416
 417                         /* free current transmit buffer */
 418                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
 419
 420                         /* this tx buffer is done */
 421                         n_hdlc->tbuf = NULL;
 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                         /* buffer not accepted by driver */
 434                         /* set this buffer as pending buffer */
 435                         n_hdlc->tbuf = tbuf;
 436                         break;
 437                 }
 438         }
 439
 440         if (!tbuf)
 441                 tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
 442
 443         /* Clear the re-entry flag */
 444         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 445         n_hdlc->tbusy = 0;
 446         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 447
 448         if (n_hdlc->woke_up)
 449           goto check_again;
 450
 451         if (debuglevel >= DEBUG_LEVEL_INFO)
 452                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
 453
 454 }       /* end of n_hdlc_send_frames() */
 455
 456 /**
 457  * n_hdlc_tty_wakeup - Callback for transmit wakeup
 458  * @tty - pointer to associated tty instance data
 459  *
 460  * Called when low level device driver can accept more send data.
 461  */
 462 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
 463 {
 464         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 465
 466         if (debuglevel >= DEBUG_LEVEL_INFO)
 467                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
 468
 469         if (!n_hdlc)
 470                 return;
 471
 472         if (tty != n_hdlc->tty) {
 473                 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
 474                 return;
 475         }
 476
 477         n_hdlc_send_frames (n_hdlc, tty);
 478
 479 }       /* end of n_hdlc_tty_wakeup() */
 480
 481 /**
 482  * n_hdlc_tty_room - Return the amount of space left in the receiver's buffer
 483  * @tty - pointer to associated tty instance data
 484  *
 485  * Callback function from tty driver. Return the amount of space left in the
 486  * receiver's buffer to decide if remote transmitter is to be throttled.
 487  */
 488 static int n_hdlc_tty_room(struct tty_struct *tty)
 489 {
 490         if (debuglevel >= DEBUG_LEVEL_INFO)
 491                 printk("%s(%d)n_hdlc_tty_room() called\n",__FILE__,__LINE__);
 492         /* always return a larger number to prevent */
 493         /* throttling of remote transmitter. */
 494         return 65536;
 495 }       /* end of n_hdlc_tty_root() */
 496
 497 /**
 498  * n_hdlc_tty_receive - Called by tty driver when receive data is available
 499  * @tty - pointer to tty instance data
 500  * @data - pointer to received data
 501  * @flags - pointer to flags for data
 502  * @count - count of received data in bytes
 503  *
 504  * Called by tty low level driver when receive data is available. Data is
 505  * interpreted as one HDLC frame.
 506  */
 507 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
 508                                char *flags, int count)
 509 {
 510         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 511         register struct n_hdlc_buf *buf;
 512
 513         if (debuglevel >= DEBUG_LEVEL_INFO)
 514                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
 515                         __FILE__,__LINE__, count);
 516
 517         /* This can happen if stuff comes in on the backup tty */
 518         if (n_hdlc == 0 || tty != n_hdlc->tty)
 519                 return;
 520
 521         /* verify line is using HDLC discipline */
 522         if (n_hdlc->magic != HDLC_MAGIC) {
 523                 printk("%s(%d) line not using HDLC discipline\n",
 524                         __FILE__,__LINE__);
 525                 return;
 526         }
 527
 528         if ( count>maxframe ) {
 529                 if (debuglevel >= DEBUG_LEVEL_INFO)
 530                         printk("%s(%d) rx count>maxframesize, data discarded\n",
 531                                __FILE__,__LINE__);
 532                 return;
 533         }
 534
 535         /* get a free HDLC buffer */
 536         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 537         if (!buf) {
 538                 /* no buffers in free list, attempt to allocate another rx buffer */
 539                 /* unless the maximum count has been reached */
 540                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
 541                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
 542         }
 543
 544         if (!buf) {
 545                 if (debuglevel >= DEBUG_LEVEL_INFO)
 546                         printk("%s(%d) no more rx buffers, data discarded\n",
 547                                __FILE__,__LINE__);
 548                 return;
 549         }
 550
 551         /* copy received data to HDLC buffer */
 552         memcpy(buf->buf,data,count);
 553         buf->count=count;
 554
 555         /* add HDLC buffer to list of received frames */
 556         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
 557
 558         /* wake up any blocked reads and perform async signalling */
 559         wake_up_interruptible (&tty->read_wait);
 560         if (n_hdlc->tty->fasync != NULL)
 561                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
 562
 563 }       /* end of n_hdlc_tty_receive() */
 564
 565 /**
 566  * n_hdlc_tty_read - Called to retreive one frame of data (if available)
 567  * @tty - pointer to tty instance data
 568  * @file - pointer to open file object
 569  * @buf - pointer to returned data buffer
 570  * @nr - size of returned data buffer
 571  *
 572  * Returns the number of bytes returned or error code.
 573  */
 574 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 575                            __u8 __user *buf, size_t nr)
 576 {
 577         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 578         int ret;
 579         struct n_hdlc_buf *rbuf;
 580
 581         if (debuglevel >= DEBUG_LEVEL_INFO)
 582                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
 583
 584         /* Validate the pointers */
 585         if (!n_hdlc)
 586                 return -EIO;
 587
 588         /* verify user access to buffer */
 589         if (!access_ok(VERIFY_WRITE, buf, nr)) {
 590                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
 591                 "buffer\n", __FILE__, __LINE__);
 592                 return -EFAULT;
 593         }
 594
 595         for (;;) {
 596                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 597                         return -EIO;
 598
 599                 n_hdlc = tty2n_hdlc (tty);
 600                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 601                          tty != n_hdlc->tty)
 602                         return 0;
 603
 604                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 605                 if (rbuf)
 606                         break;
 607
 608                 /* no data */
 609                 if (file->f_flags & O_NONBLOCK)
 610                         return -EAGAIN;
 611
 612                 interruptible_sleep_on (&tty->read_wait);
 613                 if (signal_pending(current))
 614                         return -EINTR;
 615         }
 616
 617         if (rbuf->count > nr)
 618                 /* frame too large for caller's buffer (discard frame) */
 619                 ret = -EOVERFLOW;
 620         else {
 621                 /* Copy the data to the caller's buffer */
 622                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
 623                         ret = -EFAULT;
 624                 else
 625                         ret = rbuf->count;
 626         }
 627
 628         /* return HDLC buffer to free list unless the free list */
 629         /* count has exceeded the default value, in which case the */
 630         /* buffer is freed back to the OS to conserve memory */
 631         if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
 632                 kfree(rbuf);
 633         else
 634                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
 635
 636         return ret;
 637
 638 }       /* end of n_hdlc_tty_read() */
 639
 640 /**
 641  * n_hdlc_tty_write - write a single frame of data to device
 642  * @tty - pointer to associated tty device instance data
 643  * @file - pointer to file object data
 644  * @data - pointer to transmit data (one frame)
 645  * @count - size of transmit frame in bytes
 646  *
 647  * Returns the number of bytes written (or error code).
 648  */
 649 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 650                             const unsigned char *data, size_t count)
 651 {
 652         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 653         int error = 0;
 654         DECLARE_WAITQUEUE(wait, current);
 655         struct n_hdlc_buf *tbuf;
 656
 657         if (debuglevel >= DEBUG_LEVEL_INFO)
 658                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
 659                         __FILE__,__LINE__,count);
 660
 661         /* Verify pointers */
 662         if (!n_hdlc)
 663                 return -EIO;
 664
 665         if (n_hdlc->magic != HDLC_MAGIC)
 666                 return -EIO;
 667
 668         /* verify frame size */
 669         if (count > maxframe ) {
 670                 if (debuglevel & DEBUG_LEVEL_INFO)
 671                         printk (KERN_WARNING
 672                                 "n_hdlc_tty_write: truncating user packet "
 673                                 "from %lu to %d\n", (unsigned long) count,
 674                                 maxframe );
 675                 count = maxframe;
 676         }
 677
 678         add_wait_queue(&tty->write_wait, &wait);
 679         set_current_state(TASK_INTERRUPTIBLE);
 680
 681         /* Allocate transmit buffer */
 682         /* sleep until transmit buffer available */
 683         while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
 684                 schedule();
 685
 686                 n_hdlc = tty2n_hdlc (tty);
 687                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 688                     tty != n_hdlc->tty) {
 689                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
 690                         error = -EIO;
 691                         break;
 692                 }
 693
 694                 if (signal_pending(current)) {
 695                         error = -EINTR;
 696                         break;
 697                 }
 698         }
 699
 700         set_current_state(TASK_RUNNING);
 701         remove_wait_queue(&tty->write_wait, &wait);
 702
 703         if (!error) {
 704                 /* Retrieve the user's buffer */
 705                 memcpy(tbuf->buf, data, count);
 706
 707                 /* Send the data */
 708                 tbuf->count = error = count;
 709                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
 710                 n_hdlc_send_frames(n_hdlc,tty);
 711         }
 712
 713         return error;
 714
 715 }       /* end of n_hdlc_tty_write() */
 716
 717 /**
 718  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
 719  * @tty - pointer to tty instance data
 720  * @file - pointer to open file object for device
 721  * @cmd - IOCTL command code
 722  * @arg - argument for IOCTL call (cmd dependent)
 723  *
 724  * Returns command dependent result.
 725  */
 726 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 727                             unsigned int cmd, unsigned long arg)
 728 {
 729         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 730         int error = 0;
 731         int count;
 732         unsigned long flags;
 733
 734         if (debuglevel >= DEBUG_LEVEL_INFO)
 735                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
 736                         __FILE__,__LINE__,cmd);
 737
 738         /* Verify the status of the device */
 739         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
 740                 return -EBADF;
 741
 742         switch (cmd) {
 743         case FIONREAD:
 744                 /* report count of read data available */
 745                 /* in next available frame (if any) */
 746                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
 747                 if (n_hdlc->rx_buf_list.head)
 748                         count = n_hdlc->rx_buf_list.head->count;
 749                 else
 750                         count = 0;
 751                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
 752                 error = put_user(count, (int __user *)arg);
 753                 break;
 754
 755         case TIOCOUTQ:
 756                 /* get the pending tx byte count in the driver */
 757                 count = tty->driver->chars_in_buffer ?
 758                                 tty->driver->chars_in_buffer(tty) : 0;
 759                 /* add size of next output frame in queue */
 760                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
 761                 if (n_hdlc->tx_buf_list.head)
 762                         count += n_hdlc->tx_buf_list.head->count;
 763                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
 764                 error = put_user(count, (int __user *)arg);
 765                 break;
 766
 767         default:
 768                 error = n_tty_ioctl (tty, file, cmd, arg);
 769                 break;
 770         }
 771         return error;
 772
 773 }       /* end of n_hdlc_tty_ioctl() */
 774
 775 /**
 776  * n_hdlc_tty_poll - TTY callback for poll system call
 777  * @tty - pointer to tty instance data
 778  * @filp - pointer to open file object for device
 779  * @poll_table - wait queue for operations
 780  *
 781  * Determine which operations (read/write) will not block and return info
 782  * to caller.
 783  * Returns a bit mask containing info on which ops will not block.
 784  */
 785 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 786                                     poll_table *wait)
 787 {
 788         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 789         unsigned int mask = 0;
 790
 791         if (debuglevel >= DEBUG_LEVEL_INFO)
 792                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
 793
 794         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
 795                 /* queue current process into any wait queue that */
 796                 /* may awaken in the future (read and write) */
 797
 798                 poll_wait(filp, &tty->read_wait, wait);
 799                 poll_wait(filp, &tty->write_wait, wait);
 800
 801                 /* set bits for operations that won't block */
 802                 if(n_hdlc->rx_buf_list.head)
 803                         mask |= POLLIN | POLLRDNORM;    /* readable */
 804                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 805                         mask |= POLLHUP;
 806                 if(tty_hung_up_p(filp))
 807                         mask |= POLLHUP;
 808                 if(n_hdlc->tx_free_buf_list.head)
 809                         mask |= POLLOUT | POLLWRNORM;   /* writable */
 810         }
 811         return mask;
 812 }       /* end of n_hdlc_tty_poll() */
 813
 814 /**
 815  * n_hdlc_alloc - allocate an n_hdlc instance data structure
 816  *
 817  * Returns a pointer to newly created structure if success, otherwise %NULL
 818  */
 819 static struct n_hdlc *n_hdlc_alloc(void)
 820 {
 821         struct n_hdlc_buf *buf;
 822         int i;
 823         struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
 824
 825         if (!n_hdlc)
 826                 return NULL;
 827
 828         memset(n_hdlc, 0, sizeof(*n_hdlc));
 829
 830         n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
 831         n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
 832         n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
 833         n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
 834
 835         /* allocate free rx buffer list */
 836         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
 837                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 838                 if (buf)
 839                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
 840                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 841                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
 842         }
 843
 844         /* allocate free tx buffer list */
 845         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
 846                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 847                 if (buf)
 848                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
 849                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 850                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
 851         }
 852
 853         /* Initialize the control block */
 854         n_hdlc->magic  = HDLC_MAGIC;
 855         n_hdlc->flags  = 0;
 856
 857         return n_hdlc;
 858
 859 }       /* end of n_hdlc_alloc() */
 860
 861 /**
 862  * n_hdlc_buf_list_init - initialize specified HDLC buffer list
 863  * @list - pointer to buffer list
 864  */
 865 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
 866 {
 867         memset(list, 0, sizeof(*list));
 868         spin_lock_init(&list->spinlock);
 869 }       /* end of n_hdlc_buf_list_init() */
 870
 871 /**
 872  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
 873  * @list - pointer to buffer list
 874  * @buf - pointer to buffer
 875  */
 876 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 877                            struct n_hdlc_buf *buf)
 878 {
 879         unsigned long flags;
 880         spin_lock_irqsave(&list->spinlock,flags);
 881
 882         buf->link=NULL;
 883         if(list->tail)
 884                 list->tail->link = buf;
 885         else
 886                 list->head = buf;
 887         list->tail = buf;
 888         (list->count)++;
 889
 890         spin_unlock_irqrestore(&list->spinlock,flags);
 891
 892 }       /* end of n_hdlc_buf_put() */
 893
 894 /**
 895  * n_hdlc_buf_get - remove and return an HDLC buffer from list
 896  * @list - pointer to HDLC buffer list
 897  *
 898  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
 899  * list.
 900  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
 901  */
 902 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
 903 {
 904         unsigned long flags;
 905         struct n_hdlc_buf *buf;
 906         spin_lock_irqsave(&list->spinlock,flags);
 907
 908         buf = list->head;
 909         if (buf) {
 910                 list->head = buf->link;
 911                 (list->count)--;
 912         }
 913         if (!list->head)
 914                 list->tail = NULL;
 915
 916         spin_unlock_irqrestore(&list->spinlock,flags);
 917         return buf;
 918
 919 }       /* end of n_hdlc_buf_get() */
 920
 921 static char hdlc_banner[] __initdata =
 922         KERN_INFO "HDLC line discipline: version " HDLC_VERSION
 923         ", maxframe=%u\n";
 924 static char hdlc_register_ok[] __initdata =
 925         KERN_INFO "N_HDLC line discipline registered.\n";
 926 static char hdlc_register_fail[] __initdata =
 927         KERN_ERR "error registering line discipline: %d\n";
 928 static char hdlc_init_fail[] __initdata =
 929         KERN_INFO "N_HDLC: init failure %d\n";
 930
 931 static int __init n_hdlc_init(void)
 932 {
 933         int status;
 934
 935         /* range check maxframe arg */
 936         if (maxframe < 4096)
 937                 maxframe = 4096;
 938         else if (maxframe > 65535)
 939                 maxframe = 65535;
 940
 941         printk(hdlc_banner, maxframe);
 942
 943         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
 944         if (!status)
 945                 printk(hdlc_register_ok);
 946         else
 947                 printk(hdlc_register_fail, status);
 948
 949         if (status)
 950                 printk(hdlc_init_fail, status);
 951         return status;
 952
 953 }       /* end of init_module() */
 954
 955 static char hdlc_unregister_ok[] __exitdata =
 956         KERN_INFO "N_HDLC: line discipline unregistered\n";
 957 static char hdlc_unregister_fail[] __exitdata =
 958         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
 959
 960 static void __exit n_hdlc_exit(void)
 961 {
 962         /* Release tty registration of line discipline */
 963         int status = tty_register_ldisc(N_HDLC, NULL);
 964
 965         if (status)
 966                 printk(hdlc_unregister_fail, status);
 967         else
 968                 printk(hdlc_unregister_ok);
 969 }
 970
 971 module_init(n_hdlc_init);
 972 module_exit(n_hdlc_exit);
 973
 974 MODULE_LICENSE("GPL");
 975 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
 976 module_param(debuglevel, int, 0);
 977 module_param(maxframe, int, 0);
 978 MODULE_ALIAS_LDISC(N_HDLC);