drivers/tty/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  *
  14  * This code is released under the GNU General Public License (GPL)
  15  *
  16  * This module implements the tty line discipline N_HDLC for use with
  17  * tty device drivers that support bit-synchronous HDLC communications.
  18  *
  19  * All HDLC data is frame oriented which means:
  20  *
  21  * 1. tty write calls represent one complete transmit frame of data
  22  *    The device driver should accept the complete frame or none of
  23  *    the frame (busy) in the write method. Each write call should have
  24  *    a byte count in the range of 2-65535 bytes (2 is min HDLC frame
  25  *    with 1 addr byte and 1 ctrl byte). The max byte count of 65535
  26  *    should include any crc bytes required. For example, when using
  27  *    CCITT CRC32, 4 crc bytes are required, so the maximum size frame
  28  *    the application may transmit is limited to 65531 bytes. For CCITT
  29  *    CRC16, the maximum application frame size would be 65533.
  30  *
  31  *
  32  * 2. receive callbacks from the device driver represents
  33  *    one received frame. The device driver should bypass
  34  *    the tty flip buffer and call the line discipline receive
  35  *    callback directly to avoid fragmenting or concatenating
  36  *    multiple frames into a single receive callback.
  37  *
  38  *    The HDLC line discipline queues the receive frames in separate
  39  *    buffers so complete receive frames can be returned by the
  40  *    tty read calls.
  41  *
  42  * 3. tty read calls returns an entire frame of data or nothing.
  43  *
  44  * 4. all send and receive data is considered raw. No processing
  45  *    or translation is performed by the line discipline, regardless
  46  *    of the tty flags
  47  *
  48  * 5. When line discipline is queried for the amount of receive
  49  *    data available (FIOC), 0 is returned if no data available,
  50  *    otherwise the count of the next available frame is returned.
  51  *    (instead of the sum of all received frame counts).
  52  *
  53  * These conventions allow the standard tty programming interface
  54  * to be used for synchronous HDLC applications when used with
  55  * this line discipline (or another line discipline that is frame
  56  * oriented such as N_PPP).
  57  *
  58  * The SyncLink driver (synclink.c) implements both asynchronous
  59  * (using standard line discipline N_TTY) and synchronous HDLC
  60  * (using N_HDLC) communications, with the latter using the above
  61  * conventions.
  62  *
  63  * This implementation is very basic and does not maintain
  64  * any statistics. The main point is to enforce the raw data
  65  * and frame orientation of HDLC communications.
  66  *
  67  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  68  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  69  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  70  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  71  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  72  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  73  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  74  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  75  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  76  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  77  * OF THE POSSIBILITY OF SUCH DAMAGE.
  78  */
  79
  80 #define HDLC_MAGIC 0x239e
  81
  82 #include <linux/module.h>
  83 #include <linux/init.h>
  84 #include <linux/kernel.h>
  85 #include <linux/sched.h>
  86 #include <linux/types.h>
  87 #include <linux/fcntl.h>
  88 #include <linux/interrupt.h>
  89 #include <linux/ptrace.h>
  90
  91 #undef VERSION
  92 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
  93
  94 #include <linux/poll.h>
  95 #include <linux/in.h>
  96 #include <linux/ioctl.h>
  97 #include <linux/slab.h>
  98 #include <linux/tty.h>
  99 #include <linux/errno.h>
 100 #include <linux/string.h>       /* used in new tty drivers */
 101 #include <linux/signal.h>       /* used in new tty drivers */
 102 #include <linux/if.h>
 103 #include <linux/bitops.h>
 104
 105 #include <asm/termios.h>
 106 #include <linux/uaccess.h>
 107
 108 /*
 109  * Buffers for individual HDLC frames
 110  */
 111 #define MAX_HDLC_FRAME_SIZE 65535
 112 #define DEFAULT_RX_BUF_COUNT 10
 113 #define MAX_RX_BUF_COUNT 60
 114 #define DEFAULT_TX_BUF_COUNT 3
 115
 116 struct n_hdlc_buf {
 117         struct list_head  list_item;
 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 list_head  list;
 126         int               count;
 127         spinlock_t        spinlock;
 128 };
 129
 130 /**
 131  * struct n_hdlc - per device instance data structure
 132  * @magic - magic value for structure
 133  * @flags - miscellaneous control flags
 134  * @tty - ptr to TTY structure
 135  * @backup_tty - TTY to use if tty gets closed
 136  * @tbusy - reentrancy flag for tx wakeup code
 137  * @woke_up - FIXME: describe this field
 138  * @tx_buf_list - list of pending transmit frame buffers
 139  * @rx_buf_list - list of received frame buffers
 140  * @tx_free_buf_list - list unused transmit frame buffers
 141  * @rx_free_buf_list - list unused received frame buffers
 142  */
 143 struct n_hdlc {
 144         int                     magic;
 145         __u32                   flags;
 146         struct tty_struct       *tty;
 147         struct tty_struct       *backup_tty;
 148         int                     tbusy;
 149         int                     woke_up;
 150         struct n_hdlc_buf_list  tx_buf_list;
 151         struct n_hdlc_buf_list  rx_buf_list;
 152         struct n_hdlc_buf_list  tx_free_buf_list;
 153         struct n_hdlc_buf_list  rx_free_buf_list;
 154 };
 155
 156 /*
 157  * HDLC buffer list manipulation functions
 158  */
 159 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
 160                                                 struct n_hdlc_buf *buf);
 161 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 162                            struct n_hdlc_buf *buf);
 163 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
 164
 165 /* Local functions */
 166
 167 static struct n_hdlc *n_hdlc_alloc (void);
 168
 169 /* debug level can be set by insmod for debugging purposes */
 170 #define DEBUG_LEVEL_INFO        1
 171 static int debuglevel;
 172
 173 /* max frame size for memory allocations */
 174 static int maxframe = 4096;
 175
 176 /* TTY callbacks */
 177
 178 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 179                            __u8 __user *buf, size_t nr);
 180 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 181                             const unsigned char *buf, size_t nr);
 182 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 183                             unsigned int cmd, unsigned long arg);
 184 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 185                                     poll_table *wait);
 186 static int n_hdlc_tty_open(struct tty_struct *tty);
 187 static void n_hdlc_tty_close(struct tty_struct *tty);
 188 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
 189                                char *fp, int count);
 190 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
 191
 192 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
 193
 194 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
 195 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
 196
 197 static void flush_rx_queue(struct tty_struct *tty)
 198 {
 199         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 200         struct n_hdlc_buf *buf;
 201
 202         while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
 203                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
 204 }
 205
 206 static void flush_tx_queue(struct tty_struct *tty)
 207 {
 208         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 209         struct n_hdlc_buf *buf;
 210
 211         while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
 212                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
 213 }
 214
 215 static struct tty_ldisc_ops n_hdlc_ldisc = {
 216         .owner          = THIS_MODULE,
 217         .magic          = TTY_LDISC_MAGIC,
 218         .name           = "hdlc",
 219         .open           = n_hdlc_tty_open,
 220         .close          = n_hdlc_tty_close,
 221         .read           = n_hdlc_tty_read,
 222         .write          = n_hdlc_tty_write,
 223         .ioctl          = n_hdlc_tty_ioctl,
 224         .poll           = n_hdlc_tty_poll,
 225         .receive_buf    = n_hdlc_tty_receive,
 226         .write_wakeup   = n_hdlc_tty_wakeup,
 227         .flush_buffer   = flush_rx_queue,
 228 };
 229
 230 /**
 231  * n_hdlc_release - release an n_hdlc per device line discipline info structure
 232  * @n_hdlc - per device line discipline info structure
 233  */
 234 static void n_hdlc_release(struct n_hdlc *n_hdlc)
 235 {
 236         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
 237         struct n_hdlc_buf *buf;
 238
 239         if (debuglevel >= DEBUG_LEVEL_INFO)
 240                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
 241
 242         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
 243         wake_up_interruptible (&tty->read_wait);
 244         wake_up_interruptible (&tty->write_wait);
 245
 246         if (tty->disc_data == n_hdlc)
 247                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
 248
 249         /* Release transmit and receive buffers */
 250         for(;;) {
 251                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 252                 if (buf) {
 253                         kfree(buf);
 254                 } else
 255                         break;
 256         }
 257         for(;;) {
 258                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
 259                 if (buf) {
 260                         kfree(buf);
 261                 } else
 262                         break;
 263         }
 264         for(;;) {
 265                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 266                 if (buf) {
 267                         kfree(buf);
 268                 } else
 269                         break;
 270         }
 271         for(;;) {
 272                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 273                 if (buf) {
 274                         kfree(buf);
 275                 } else
 276                         break;
 277         }
 278         kfree(n_hdlc);
 279
 280 }       /* end of n_hdlc_release() */
 281
 282 /**
 283  * n_hdlc_tty_close - line discipline close
 284  * @tty - pointer to tty info structure
 285  *
 286  * Called when the line discipline is changed to something
 287  * else, the tty is closed, or the tty detects a hangup.
 288  */
 289 static void n_hdlc_tty_close(struct tty_struct *tty)
 290 {
 291         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 292
 293         if (debuglevel >= DEBUG_LEVEL_INFO)
 294                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
 295
 296         if (n_hdlc != NULL) {
 297                 if (n_hdlc->magic != HDLC_MAGIC) {
 298                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
 299                         return;
 300                 }
 301 #if defined(TTY_NO_WRITE_SPLIT)
 302                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 303 #endif
 304                 tty->disc_data = NULL;
 305                 if (tty == n_hdlc->backup_tty)
 306                         n_hdlc->backup_tty = NULL;
 307                 if (tty != n_hdlc->tty)
 308                         return;
 309                 if (n_hdlc->backup_tty) {
 310                         n_hdlc->tty = n_hdlc->backup_tty;
 311                 } else {
 312                         n_hdlc_release (n_hdlc);
 313                 }
 314         }
 315
 316         if (debuglevel >= DEBUG_LEVEL_INFO)
 317                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
 318
 319 }       /* end of n_hdlc_tty_close() */
 320
 321 /**
 322  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
 323  * @tty - pointer to tty info structure
 324  *
 325  * Returns 0 if success, otherwise error code
 326  */
 327 static int n_hdlc_tty_open (struct tty_struct *tty)
 328 {
 329         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 330
 331         if (debuglevel >= DEBUG_LEVEL_INFO)
 332                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
 333                 __FILE__,__LINE__,
 334                 tty->name);
 335
 336         /* There should not be an existing table for this slot. */
 337         if (n_hdlc) {
 338                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
 339                 return -EEXIST;
 340         }
 341
 342         n_hdlc = n_hdlc_alloc();
 343         if (!n_hdlc) {
 344                 printk (KERN_ERR "n_hdlc_alloc failed\n");
 345                 return -ENFILE;
 346         }
 347
 348         tty->disc_data = n_hdlc;
 349         n_hdlc->tty    = tty;
 350         tty->receive_room = 65536;
 351
 352 #if defined(TTY_NO_WRITE_SPLIT)
 353         /* change tty_io write() to not split large writes into 8K chunks */
 354         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 355 #endif
 356
 357         /* flush receive data from driver */
 358         tty_driver_flush_buffer(tty);
 359
 360         if (debuglevel >= DEBUG_LEVEL_INFO)
 361                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
 362
 363         return 0;
 364
 365 }       /* end of n_tty_hdlc_open() */
 366
 367 /**
 368  * n_hdlc_send_frames - send frames on pending send buffer list
 369  * @n_hdlc - pointer to ldisc instance data
 370  * @tty - pointer to tty instance data
 371  *
 372  * Send frames on pending send buffer list until the driver does not accept a
 373  * frame (busy) this function is called after adding a frame to the send buffer
 374  * list and by the tty wakeup callback.
 375  */
 376 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 377 {
 378         register int actual;
 379         unsigned long flags;
 380         struct n_hdlc_buf *tbuf;
 381
 382         if (debuglevel >= DEBUG_LEVEL_INFO)
 383                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
 384  check_again:
 385
 386         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 387         if (n_hdlc->tbusy) {
 388                 n_hdlc->woke_up = 1;
 389                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 390                 return;
 391         }
 392         n_hdlc->tbusy = 1;
 393         n_hdlc->woke_up = 0;
 394         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 395
 396         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 397         while (tbuf) {
 398                 if (debuglevel >= DEBUG_LEVEL_INFO)
 399                         printk("%s(%d)sending frame %p, count=%d\n",
 400                                 __FILE__,__LINE__,tbuf,tbuf->count);
 401
 402                 /* Send the next block of data to device */
 403                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 404                 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
 405
 406                 /* rollback was possible and has been done */
 407                 if (actual == -ERESTARTSYS) {
 408                         n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
 409                         break;
 410                 }
 411                 /* if transmit error, throw frame away by */
 412                 /* pretending it was accepted by driver */
 413                 if (actual < 0)
 414                         actual = tbuf->count;
 415
 416                 if (actual == tbuf->count) {
 417                         if (debuglevel >= DEBUG_LEVEL_INFO)
 418                                 printk("%s(%d)frame %p completed\n",
 419                                         __FILE__,__LINE__,tbuf);
 420
 421                         /* free current transmit buffer */
 422                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
 423
 424                         /* wait up sleeping writers */
 425                         wake_up_interruptible(&tty->write_wait);
 426
 427                         /* get next pending transmit buffer */
 428                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 429                 } else {
 430                         if (debuglevel >= DEBUG_LEVEL_INFO)
 431                                 printk("%s(%d)frame %p pending\n",
 432                                         __FILE__,__LINE__,tbuf);
 433
 434                         /*
 435                          * the buffer was not accepted by driver,
 436                          * return it back into tx queue
 437                          */
 438                         n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
 439                         break;
 440                 }
 441         }
 442
 443         if (!tbuf)
 444                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 445
 446         /* Clear the re-entry flag */
 447         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 448         n_hdlc->tbusy = 0;
 449         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 450
 451         if (n_hdlc->woke_up)
 452           goto check_again;
 453
 454         if (debuglevel >= DEBUG_LEVEL_INFO)
 455                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
 456
 457 }       /* end of n_hdlc_send_frames() */
 458
 459 /**
 460  * n_hdlc_tty_wakeup - Callback for transmit wakeup
 461  * @tty - pointer to associated tty instance data
 462  *
 463  * Called when low level device driver can accept more send data.
 464  */
 465 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
 466 {
 467         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 468
 469         if (debuglevel >= DEBUG_LEVEL_INFO)
 470                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
 471
 472         if (!n_hdlc)
 473                 return;
 474
 475         if (tty != n_hdlc->tty) {
 476                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 477                 return;
 478         }
 479
 480         n_hdlc_send_frames (n_hdlc, tty);
 481
 482 }       /* end of n_hdlc_tty_wakeup() */
 483
 484 /**
 485  * n_hdlc_tty_receive - Called by tty driver when receive data is available
 486  * @tty - pointer to tty instance data
 487  * @data - pointer to received data
 488  * @flags - pointer to flags for data
 489  * @count - count of received data in bytes
 490  *
 491  * Called by tty low level driver when receive data is available. Data is
 492  * interpreted as one HDLC frame.
 493  */
 494 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
 495                                char *flags, int count)
 496 {
 497         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 498         register struct n_hdlc_buf *buf;
 499
 500         if (debuglevel >= DEBUG_LEVEL_INFO)
 501                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
 502                         __FILE__,__LINE__, count);
 503
 504         /* This can happen if stuff comes in on the backup tty */
 505         if (!n_hdlc || tty != n_hdlc->tty)
 506                 return;
 507
 508         /* verify line is using HDLC discipline */
 509         if (n_hdlc->magic != HDLC_MAGIC) {
 510                 printk("%s(%d) line not using HDLC discipline\n",
 511                         __FILE__,__LINE__);
 512                 return;
 513         }
 514
 515         if ( count>maxframe ) {
 516                 if (debuglevel >= DEBUG_LEVEL_INFO)
 517                         printk("%s(%d) rx count>maxframesize, data discarded\n",
 518                                __FILE__,__LINE__);
 519                 return;
 520         }
 521
 522         /* get a free HDLC buffer */
 523         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 524         if (!buf) {
 525                 /* no buffers in free list, attempt to allocate another rx buffer */
 526                 /* unless the maximum count has been reached */
 527                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
 528                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
 529         }
 530
 531         if (!buf) {
 532                 if (debuglevel >= DEBUG_LEVEL_INFO)
 533                         printk("%s(%d) no more rx buffers, data discarded\n",
 534                                __FILE__,__LINE__);
 535                 return;
 536         }
 537
 538         /* copy received data to HDLC buffer */
 539         memcpy(buf->buf,data,count);
 540         buf->count=count;
 541
 542         /* add HDLC buffer to list of received frames */
 543         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
 544
 545         /* wake up any blocked reads and perform async signalling */
 546         wake_up_interruptible (&tty->read_wait);
 547         if (n_hdlc->tty->fasync != NULL)
 548                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
 549
 550 }       /* end of n_hdlc_tty_receive() */
 551
 552 /**
 553  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
 554  * @tty - pointer to tty instance data
 555  * @file - pointer to open file object
 556  * @buf - pointer to returned data buffer
 557  * @nr - size of returned data buffer
 558  *
 559  * Returns the number of bytes returned or error code.
 560  */
 561 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 562                            __u8 __user *buf, size_t nr)
 563 {
 564         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 565         int ret = 0;
 566         struct n_hdlc_buf *rbuf;
 567         DECLARE_WAITQUEUE(wait, current);
 568
 569         if (debuglevel >= DEBUG_LEVEL_INFO)
 570                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
 571
 572         /* Validate the pointers */
 573         if (!n_hdlc)
 574                 return -EIO;
 575
 576         /* verify user access to buffer */
 577         if (!access_ok(VERIFY_WRITE, buf, nr)) {
 578                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
 579                 "buffer\n", __FILE__, __LINE__);
 580                 return -EFAULT;
 581         }
 582
 583         add_wait_queue(&tty->read_wait, &wait);
 584
 585         for (;;) {
 586                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
 587                         ret = -EIO;
 588                         break;
 589                 }
 590                 if (tty_hung_up_p(file))
 591                         break;
 592
 593                 set_current_state(TASK_INTERRUPTIBLE);
 594
 595                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 596                 if (rbuf) {
 597                         if (rbuf->count > nr) {
 598                                 /* too large for caller's buffer */
 599                                 ret = -EOVERFLOW;
 600                         } else {
 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 (file->f_flags & O_NONBLOCK) {
 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 (file->f_flags & O_NONBLOCK) {
 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 unsigned int 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         unsigned int 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 |= POLLIN | POLLRDNORM;    /* readable */
 819                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 820                         mask |= POLLHUP;
 821                 if (tty_hung_up_p(filp))
 822                         mask |= POLLHUP;
 823                 if (!tty_is_writelocked(tty) &&
 824                                 !list_empty(&n_hdlc->tx_free_buf_list.list))
 825                         mask |= POLLOUT | POLLWRNORM;   /* 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 char hdlc_banner[] __initdata =
 943         KERN_INFO "HDLC line discipline maxframe=%u\n";
 944 static char hdlc_register_ok[] __initdata =
 945         KERN_INFO "N_HDLC line discipline registered.\n";
 946 static char hdlc_register_fail[] __initdata =
 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 static char hdlc_unregister_ok[] __exitdata =
 972         KERN_INFO "N_HDLC: line discipline unregistered\n";
 973 static char hdlc_unregister_fail[] __exitdata =
 974         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
 975
 976 static void __exit n_hdlc_exit(void)
 977 {
 978         /* Release tty registration of line discipline */
 979         int status = tty_unregister_ldisc(N_HDLC);
 980
 981         if (status)
 982                 printk(hdlc_unregister_fail, status);
 983         else
 984                 printk(hdlc_unregister_ok);
 985 }
 986
 987 module_init(n_hdlc_init);
 988 module_exit(n_hdlc_exit);
 989
 990 MODULE_LICENSE("GPL");
 991 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
 992 module_param(debuglevel, int, 0);
 993 module_param(maxframe, int, 0);
 994 MODULE_ALIAS_LDISC(N_HDLC);