drivers/tty/tty_port.c

   1 /*
   2  * Tty port functions
   3  */
   4
   5 #include <linux/types.h>
   6 #include <linux/errno.h>
   7 #include <linux/tty.h>
   8 #include <linux/tty_driver.h>
   9 #include <linux/tty_flip.h>
  10 #include <linux/serial.h>
  11 #include <linux/timer.h>
  12 #include <linux/string.h>
  13 #include <linux/slab.h>
  14 #include <linux/sched.h>
  15 #include <linux/init.h>
  16 #include <linux/wait.h>
  17 #include <linux/bitops.h>
  18 #include <linux/delay.h>
  19 #include <linux/module.h>
  20
  21 void tty_port_init(struct tty_port *port)
  22 {
  23         memset(port, 0, sizeof(*port));
  24         init_waitqueue_head(&port->open_wait);
  25         init_waitqueue_head(&port->close_wait);
  26         init_waitqueue_head(&port->delta_msr_wait);
  27         mutex_init(&port->mutex);
  28         mutex_init(&port->buf_mutex);
  29         spin_lock_init(&port->lock);
  30         port->close_delay = (50 * HZ) / 100;
  31         port->closing_wait = (3000 * HZ) / 100;
  32         kref_init(&port->kref);
  33 }
  34 EXPORT_SYMBOL(tty_port_init);
  35
  36 int tty_port_alloc_xmit_buf(struct tty_port *port)
  37 {
  38         /* We may sleep in get_zeroed_page() */
  39         mutex_lock(&port->buf_mutex);
  40         if (port->xmit_buf == NULL)
  41                 port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
  42         mutex_unlock(&port->buf_mutex);
  43         if (port->xmit_buf == NULL)
  44                 return -ENOMEM;
  45         return 0;
  46 }
  47 EXPORT_SYMBOL(tty_port_alloc_xmit_buf);
  48
  49 void tty_port_free_xmit_buf(struct tty_port *port)
  50 {
  51         mutex_lock(&port->buf_mutex);
  52         if (port->xmit_buf != NULL) {
  53                 free_page((unsigned long)port->xmit_buf);
  54                 port->xmit_buf = NULL;
  55         }
  56         mutex_unlock(&port->buf_mutex);
  57 }
  58 EXPORT_SYMBOL(tty_port_free_xmit_buf);
  59
  60 static void tty_port_destructor(struct kref *kref)
  61 {
  62         struct tty_port *port = container_of(kref, struct tty_port, kref);
  63         if (port->xmit_buf)
  64                 free_page((unsigned long)port->xmit_buf);
  65         if (port->ops->destruct)
  66                 port->ops->destruct(port);
  67         else
  68                 kfree(port);
  69 }
  70
  71 void tty_port_put(struct tty_port *port)
  72 {
  73         if (port)
  74                 kref_put(&port->kref, tty_port_destructor);
  75 }
  76 EXPORT_SYMBOL(tty_port_put);
  77
  78 /**
  79  *      tty_port_tty_get        -       get a tty reference
  80  *      @port: tty port
  81  *
  82  *      Return a refcount protected tty instance or NULL if the port is not
  83  *      associated with a tty (eg due to close or hangup)
  84  */
  85
  86 struct tty_struct *tty_port_tty_get(struct tty_port *port)
  87 {
  88         unsigned long flags;
  89         struct tty_struct *tty;
  90
  91         spin_lock_irqsave(&port->lock, flags);
  92         tty = tty_kref_get(port->tty);
  93         spin_unlock_irqrestore(&port->lock, flags);
  94         return tty;
  95 }
  96 EXPORT_SYMBOL(tty_port_tty_get);
  97
  98 /**
  99  *      tty_port_tty_set        -       set the tty of a port
 100  *      @port: tty port
 101  *      @tty: the tty
 102  *
 103  *      Associate the port and tty pair. Manages any internal refcounts.
 104  *      Pass NULL to deassociate a port
 105  */
 106
 107 void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty)
 108 {
 109         unsigned long flags;
 110
 111         spin_lock_irqsave(&port->lock, flags);
 112         if (port->tty)
 113                 tty_kref_put(port->tty);
 114         port->tty = tty_kref_get(tty);
 115         spin_unlock_irqrestore(&port->lock, flags);
 116 }
 117 EXPORT_SYMBOL(tty_port_tty_set);
 118
 119 static void tty_port_shutdown(struct tty_port *port)
 120 {
 121         mutex_lock(&port->mutex);
 122         if (port->ops->shutdown && !port->console &&
 123                 test_and_clear_bit(ASYNCB_INITIALIZED, &port->flags))
 124                         port->ops->shutdown(port);
 125         mutex_unlock(&port->mutex);
 126 }
 127
 128 /**
 129  *      tty_port_hangup         -       hangup helper
 130  *      @port: tty port
 131  *
 132  *      Perform port level tty hangup flag and count changes. Drop the tty
 133  *      reference.
 134  */
 135
 136 void tty_port_hangup(struct tty_port *port)
 137 {
 138         unsigned long flags;
 139
 140         spin_lock_irqsave(&port->lock, flags);
 141         port->count = 0;
 142         port->flags &= ~ASYNC_NORMAL_ACTIVE;
 143         if (port->tty) {
 144                 set_bit(TTY_IO_ERROR, &port->tty->flags);
 145                 tty_kref_put(port->tty);
 146         }
 147         port->tty = NULL;
 148         spin_unlock_irqrestore(&port->lock, flags);
 149         wake_up_interruptible(&port->open_wait);
 150         wake_up_interruptible(&port->delta_msr_wait);
 151         tty_port_shutdown(port);
 152 }
 153 EXPORT_SYMBOL(tty_port_hangup);
 154
 155 /**
 156  *      tty_port_carrier_raised -       carrier raised check
 157  *      @port: tty port
 158  *
 159  *      Wrapper for the carrier detect logic. For the moment this is used
 160  *      to hide some internal details. This will eventually become entirely
 161  *      internal to the tty port.
 162  */
 163
 164 int tty_port_carrier_raised(struct tty_port *port)
 165 {
 166         if (port->ops->carrier_raised == NULL)
 167                 return 1;
 168         return port->ops->carrier_raised(port);
 169 }
 170 EXPORT_SYMBOL(tty_port_carrier_raised);
 171
 172 /**
 173  *      tty_port_raise_dtr_rts  -       Raise DTR/RTS
 174  *      @port: tty port
 175  *
 176  *      Wrapper for the DTR/RTS raise logic. For the moment this is used
 177  *      to hide some internal details. This will eventually become entirely
 178  *      internal to the tty port.
 179  */
 180
 181 void tty_port_raise_dtr_rts(struct tty_port *port)
 182 {
 183         if (port->ops->dtr_rts)
 184                 port->ops->dtr_rts(port, 1);
 185 }
 186 EXPORT_SYMBOL(tty_port_raise_dtr_rts);
 187
 188 /**
 189  *      tty_port_lower_dtr_rts  -       Lower DTR/RTS
 190  *      @port: tty port
 191  *
 192  *      Wrapper for the DTR/RTS raise logic. For the moment this is used
 193  *      to hide some internal details. This will eventually become entirely
 194  *      internal to the tty port.
 195  */
 196
 197 void tty_port_lower_dtr_rts(struct tty_port *port)
 198 {
 199         if (port->ops->dtr_rts)
 200                 port->ops->dtr_rts(port, 0);
 201 }
 202 EXPORT_SYMBOL(tty_port_lower_dtr_rts);
 203
 204 /**
 205  *      tty_port_block_til_ready        -       Waiting logic for tty open
 206  *      @port: the tty port being opened
 207  *      @tty: the tty device being bound
 208  *      @filp: the file pointer of the opener
 209  *
 210  *      Implement the core POSIX/SuS tty behaviour when opening a tty device.
 211  *      Handles:
 212  *              - hangup (both before and during)
 213  *              - non blocking open
 214  *              - rts/dtr/dcd
 215  *              - signals
 216  *              - port flags and counts
 217  *
 218  *      The passed tty_port must implement the carrier_raised method if it can
 219  *      do carrier detect and the dtr_rts method if it supports software
 220  *      management of these lines. Note that the dtr/rts raise is done each
 221  *      iteration as a hangup may have previously dropped them while we wait.
 222  */
 223
 224 int tty_port_block_til_ready(struct tty_port *port,
 225                                 struct tty_struct *tty, struct file *filp)
 226 {
 227         int do_clocal = 0, retval;
 228         unsigned long flags;
 229         DEFINE_WAIT(wait);
 230
 231         /* block if port is in the process of being closed */
 232         if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
 233                 wait_event_interruptible_tty(port->close_wait,
 234                                 !(port->flags & ASYNC_CLOSING));
 235                 if (port->flags & ASYNC_HUP_NOTIFY)
 236                         return -EAGAIN;
 237                 else
 238                         return -ERESTARTSYS;
 239         }
 240
 241         /* if non-blocking mode is set we can pass directly to open unless
 242            the port has just hung up or is in another error state */
 243         if (tty->flags & (1 << TTY_IO_ERROR)) {
 244                 port->flags |= ASYNC_NORMAL_ACTIVE;
 245                 return 0;
 246         }
 247         if (filp->f_flags & O_NONBLOCK) {
 248                 /* Indicate we are open */
 249                 if (tty->termios->c_cflag & CBAUD)
 250                         tty_port_raise_dtr_rts(port);
 251                 port->flags |= ASYNC_NORMAL_ACTIVE;
 252                 return 0;
 253         }
 254
 255         if (C_CLOCAL(tty))
 256                 do_clocal = 1;
 257
 258         /* Block waiting until we can proceed. We may need to wait for the
 259            carrier, but we must also wait for any close that is in progress
 260            before the next open may complete */
 261
 262         retval = 0;
 263
 264         /* The port lock protects the port counts */
 265         spin_lock_irqsave(&port->lock, flags);
 266         if (!tty_hung_up_p(filp))
 267                 port->count--;
 268         port->blocked_open++;
 269         spin_unlock_irqrestore(&port->lock, flags);
 270
 271         while (1) {
 272                 /* Indicate we are open */
 273                 if (tty->termios->c_cflag & CBAUD)
 274                         tty_port_raise_dtr_rts(port);
 275
 276                 prepare_to_wait(&port->open_wait, &wait, TASK_INTERRUPTIBLE);
 277                 /* Check for a hangup or uninitialised port.
 278                                                         Return accordingly */
 279                 if (tty_hung_up_p(filp) || !(port->flags & ASYNC_INITIALIZED)) {
 280                         if (port->flags & ASYNC_HUP_NOTIFY)
 281                                 retval = -EAGAIN;
 282                         else
 283                                 retval = -ERESTARTSYS;
 284                         break;
 285                 }
 286                 /*
 287                  * Probe the carrier. For devices with no carrier detect
 288                  * tty_port_carrier_raised will always return true.
 289                  * Never ask drivers if CLOCAL is set, this causes troubles
 290                  * on some hardware.
 291                  */
 292                 if (!(port->flags & ASYNC_CLOSING) &&
 293                                 (do_clocal || tty_port_carrier_raised(port)))
 294                         break;
 295                 if (signal_pending(current)) {
 296                         retval = -ERESTARTSYS;
 297                         break;
 298                 }
 299                 tty_unlock();
 300                 schedule();
 301                 tty_lock();
 302         }
 303         finish_wait(&port->open_wait, &wait);
 304
 305         /* Update counts. A parallel hangup will have set count to zero and
 306            we must not mess that up further */
 307         spin_lock_irqsave(&port->lock, flags);
 308         if (!tty_hung_up_p(filp))
 309                 port->count++;
 310         port->blocked_open--;
 311         if (retval == 0)
 312                 port->flags |= ASYNC_NORMAL_ACTIVE;
 313         spin_unlock_irqrestore(&port->lock, flags);
 314         return retval;
 315 }
 316 EXPORT_SYMBOL(tty_port_block_til_ready);
 317
 318 int tty_port_close_start(struct tty_port *port,
 319                                 struct tty_struct *tty, struct file *filp)
 320 {
 321         unsigned long flags;
 322
 323         spin_lock_irqsave(&port->lock, flags);
 324         if (tty_hung_up_p(filp)) {
 325                 spin_unlock_irqrestore(&port->lock, flags);
 326                 return 0;
 327         }
 328
 329         if (tty->count == 1 && port->count != 1) {
 330                 printk(KERN_WARNING
 331                     "tty_port_close_start: tty->count = 1 port count = %d.\n",
 332                                                                 port->count);
 333                 port->count = 1;
 334         }
 335         if (--port->count < 0) {
 336                 printk(KERN_WARNING "tty_port_close_start: count = %d\n",
 337                                                                 port->count);
 338                 port->count = 0;
 339         }
 340
 341         if (port->count) {
 342                 spin_unlock_irqrestore(&port->lock, flags);
 343                 if (port->ops->drop)
 344                         port->ops->drop(port);
 345                 return 0;
 346         }
 347         set_bit(ASYNCB_CLOSING, &port->flags);
 348         tty->closing = 1;
 349         spin_unlock_irqrestore(&port->lock, flags);
 350         /* Don't block on a stalled port, just pull the chain */
 351         if (tty->flow_stopped)
 352                 tty_driver_flush_buffer(tty);
 353         if (test_bit(ASYNCB_INITIALIZED, &port->flags) &&
 354                         port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
 355                 tty_wait_until_sent_from_close(tty, port->closing_wait);
 356         if (port->drain_delay) {
 357                 unsigned int bps = tty_get_baud_rate(tty);
 358                 long timeout;
 359
 360                 if (bps > 1200)
 361                         timeout = max_t(long,
 362                                 (HZ * 10 * port->drain_delay) / bps, HZ / 10);
 363                 else
 364                         timeout = 2 * HZ;
 365                 schedule_timeout_interruptible(timeout);
 366         }
 367         /* Flush the ldisc buffering */
 368         tty_ldisc_flush(tty);
 369
 370         /* Drop DTR/RTS if HUPCL is set. This causes any attached modem to
 371            hang up the line */
 372         if (tty->termios->c_cflag & HUPCL)
 373                 tty_port_lower_dtr_rts(port);
 374
 375         /* Don't call port->drop for the last reference. Callers will want
 376            to drop the last active reference in ->shutdown() or the tty
 377            shutdown path */
 378         return 1;
 379 }
 380 EXPORT_SYMBOL(tty_port_close_start);
 381
 382 void tty_port_close_end(struct tty_port *port, struct tty_struct *tty)
 383 {
 384         unsigned long flags;
 385
 386         spin_lock_irqsave(&port->lock, flags);
 387         tty->closing = 0;
 388
 389         if (port->blocked_open) {
 390                 spin_unlock_irqrestore(&port->lock, flags);
 391                 if (port->close_delay) {
 392                         msleep_interruptible(
 393                                 jiffies_to_msecs(port->close_delay));
 394                 }
 395                 spin_lock_irqsave(&port->lock, flags);
 396                 wake_up_interruptible(&port->open_wait);
 397         }
 398         port->flags &= ~(ASYNC_NORMAL_ACTIVE | ASYNC_CLOSING);
 399         wake_up_interruptible(&port->close_wait);
 400         spin_unlock_irqrestore(&port->lock, flags);
 401 }
 402 EXPORT_SYMBOL(tty_port_close_end);
 403
 404 void tty_port_close(struct tty_port *port, struct tty_struct *tty,
 405                                                         struct file *filp)
 406 {
 407         if (tty_port_close_start(port, tty, filp) == 0)
 408                 return;
 409         tty_port_shutdown(port);
 410         set_bit(TTY_IO_ERROR, &tty->flags);
 411         tty_port_close_end(port, tty);
 412         tty_port_tty_set(port, NULL);
 413 }
 414 EXPORT_SYMBOL(tty_port_close);
 415
 416 int tty_port_open(struct tty_port *port, struct tty_struct *tty,
 417                                                         struct file *filp)
 418 {
 419         spin_lock_irq(&port->lock);
 420         if (!tty_hung_up_p(filp))
 421                 ++port->count;
 422         spin_unlock_irq(&port->lock);
 423         tty_port_tty_set(port, tty);
 424
 425         /*
 426          * Do the device-specific open only if the hardware isn't
 427          * already initialized. Serialize open and shutdown using the
 428          * port mutex.
 429          */
 430
 431         mutex_lock(&port->mutex);
 432
 433         if (!test_bit(ASYNCB_INITIALIZED, &port->flags)) {
 434                 clear_bit(TTY_IO_ERROR, &tty->flags);
 435                 if (port->ops->activate) {
 436                         int retval = port->ops->activate(port, tty);
 437                         if (retval) {
 438                                 mutex_unlock(&port->mutex);
 439                                 return retval;
 440                         }
 441                 }
 442                 set_bit(ASYNCB_INITIALIZED, &port->flags);
 443         }
 444         mutex_unlock(&port->mutex);
 445         return tty_port_block_til_ready(port, tty, filp);
 446 }
 447
 448 EXPORT_SYMBOL(tty_port_open);