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