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 <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_CLOSED, &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_CLOSED, &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);