Root/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
21void tty_port_init(struct tty_port *port)
22{
23    memset(port, 0, sizeof(*port));
24    tty_buffer_init(port);
25    init_waitqueue_head(&port->open_wait);
26    init_waitqueue_head(&port->close_wait);
27    init_waitqueue_head(&port->delta_msr_wait);
28    mutex_init(&port->mutex);
29    mutex_init(&port->buf_mutex);
30    spin_lock_init(&port->lock);
31    port->close_delay = (50 * HZ) / 100;
32    port->closing_wait = (3000 * HZ) / 100;
33    kref_init(&port->kref);
34}
35EXPORT_SYMBOL(tty_port_init);
36
37/**
38 * tty_port_link_device - link tty and tty_port
39 * @port: tty_port of the device
40 * @driver: tty_driver for this device
41 * @index: index of the tty
42 *
43 * Provide the tty layer wit ha link from a tty (specified by @index) to a
44 * tty_port (@port). Use this only if neither tty_port_register_device nor
45 * tty_port_install is used in the driver. If used, this has to be called before
46 * tty_register_driver.
47 */
48void tty_port_link_device(struct tty_port *port,
49        struct tty_driver *driver, unsigned index)
50{
51    if (WARN_ON(index >= driver->num))
52        return;
53    driver->ports[index] = port;
54}
55EXPORT_SYMBOL_GPL(tty_port_link_device);
56
57/**
58 * tty_port_register_device - register tty device
59 * @port: tty_port of the device
60 * @driver: tty_driver for this device
61 * @index: index of the tty
62 * @device: parent if exists, otherwise NULL
63 *
64 * It is the same as tty_register_device except the provided @port is linked to
65 * a concrete tty specified by @index. Use this or tty_port_install (or both).
66 * Call tty_port_link_device as a last resort.
67 */
68struct device *tty_port_register_device(struct tty_port *port,
69        struct tty_driver *driver, unsigned index,
70        struct device *device)
71{
72    tty_port_link_device(port, driver, index);
73    return tty_register_device(driver, index, device);
74}
75EXPORT_SYMBOL_GPL(tty_port_register_device);
76
77/**
78 * tty_port_register_device_attr - register tty device
79 * @port: tty_port of the device
80 * @driver: tty_driver for this device
81 * @index: index of the tty
82 * @device: parent if exists, otherwise NULL
83 * @drvdata: Driver data to be set to device.
84 * @attr_grp: Attribute group to be set on device.
85 *
86 * It is the same as tty_register_device_attr except the provided @port is
87 * linked to a concrete tty specified by @index. Use this or tty_port_install
88 * (or both). Call tty_port_link_device as a last resort.
89 */
90struct device *tty_port_register_device_attr(struct tty_port *port,
91        struct tty_driver *driver, unsigned index,
92        struct device *device, void *drvdata,
93        const struct attribute_group **attr_grp)
94{
95    tty_port_link_device(port, driver, index);
96    return tty_register_device_attr(driver, index, device, drvdata,
97            attr_grp);
98}
99EXPORT_SYMBOL_GPL(tty_port_register_device_attr);
100
101int tty_port_alloc_xmit_buf(struct tty_port *port)
102{
103    /* We may sleep in get_zeroed_page() */
104    mutex_lock(&port->buf_mutex);
105    if (port->xmit_buf == NULL)
106        port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
107    mutex_unlock(&port->buf_mutex);
108    if (port->xmit_buf == NULL)
109        return -ENOMEM;
110    return 0;
111}
112EXPORT_SYMBOL(tty_port_alloc_xmit_buf);
113
114void tty_port_free_xmit_buf(struct tty_port *port)
115{
116    mutex_lock(&port->buf_mutex);
117    if (port->xmit_buf != NULL) {
118        free_page((unsigned long)port->xmit_buf);
119        port->xmit_buf = NULL;
120    }
121    mutex_unlock(&port->buf_mutex);
122}
123EXPORT_SYMBOL(tty_port_free_xmit_buf);
124
125/**
126 * tty_port_destroy -- destroy inited port
127 * @port: tty port to be doestroyed
128 *
129 * When a port was initialized using tty_port_init, one has to destroy the
130 * port by this function. Either indirectly by using tty_port refcounting
131 * (tty_port_put) or directly if refcounting is not used.
132 */
133void tty_port_destroy(struct tty_port *port)
134{
135    tty_buffer_free_all(port);
136}
137EXPORT_SYMBOL(tty_port_destroy);
138
139static void tty_port_destructor(struct kref *kref)
140{
141    struct tty_port *port = container_of(kref, struct tty_port, kref);
142    if (port->xmit_buf)
143        free_page((unsigned long)port->xmit_buf);
144    tty_port_destroy(port);
145    if (port->ops && port->ops->destruct)
146        port->ops->destruct(port);
147    else
148        kfree(port);
149}
150
151void tty_port_put(struct tty_port *port)
152{
153    if (port)
154        kref_put(&port->kref, tty_port_destructor);
155}
156EXPORT_SYMBOL(tty_port_put);
157
158/**
159 * tty_port_tty_get - get a tty reference
160 * @port: tty port
161 *
162 * Return a refcount protected tty instance or NULL if the port is not
163 * associated with a tty (eg due to close or hangup)
164 */
165
166struct tty_struct *tty_port_tty_get(struct tty_port *port)
167{
168    unsigned long flags;
169    struct tty_struct *tty;
170
171    spin_lock_irqsave(&port->lock, flags);
172    tty = tty_kref_get(port->tty);
173    spin_unlock_irqrestore(&port->lock, flags);
174    return tty;
175}
176EXPORT_SYMBOL(tty_port_tty_get);
177
178/**
179 * tty_port_tty_set - set the tty of a port
180 * @port: tty port
181 * @tty: the tty
182 *
183 * Associate the port and tty pair. Manages any internal refcounts.
184 * Pass NULL to deassociate a port
185 */
186
187void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty)
188{
189    unsigned long flags;
190
191    spin_lock_irqsave(&port->lock, flags);
192    if (port->tty)
193        tty_kref_put(port->tty);
194    port->tty = tty_kref_get(tty);
195    spin_unlock_irqrestore(&port->lock, flags);
196}
197EXPORT_SYMBOL(tty_port_tty_set);
198
199static void tty_port_shutdown(struct tty_port *port)
200{
201    mutex_lock(&port->mutex);
202    if (port->ops->shutdown && !port->console &&
203        test_and_clear_bit(ASYNCB_INITIALIZED, &port->flags))
204            port->ops->shutdown(port);
205    mutex_unlock(&port->mutex);
206}
207
208/**
209 * tty_port_hangup - hangup helper
210 * @port: tty port
211 *
212 * Perform port level tty hangup flag and count changes. Drop the tty
213 * reference.
214 */
215
216void tty_port_hangup(struct tty_port *port)
217{
218    unsigned long flags;
219
220    spin_lock_irqsave(&port->lock, flags);
221    port->count = 0;
222    port->flags &= ~ASYNC_NORMAL_ACTIVE;
223    if (port->tty) {
224        set_bit(TTY_IO_ERROR, &port->tty->flags);
225        tty_kref_put(port->tty);
226    }
227    port->tty = NULL;
228    spin_unlock_irqrestore(&port->lock, flags);
229    wake_up_interruptible(&port->open_wait);
230    wake_up_interruptible(&port->delta_msr_wait);
231    tty_port_shutdown(port);
232}
233EXPORT_SYMBOL(tty_port_hangup);
234
235/**
236 * tty_port_carrier_raised - carrier raised check
237 * @port: tty port
238 *
239 * Wrapper for the carrier detect logic. For the moment this is used
240 * to hide some internal details. This will eventually become entirely
241 * internal to the tty port.
242 */
243
244int tty_port_carrier_raised(struct tty_port *port)
245{
246    if (port->ops->carrier_raised == NULL)
247        return 1;
248    return port->ops->carrier_raised(port);
249}
250EXPORT_SYMBOL(tty_port_carrier_raised);
251
252/**
253 * tty_port_raise_dtr_rts - Raise DTR/RTS
254 * @port: tty port
255 *
256 * Wrapper for the DTR/RTS raise logic. For the moment this is used
257 * to hide some internal details. This will eventually become entirely
258 * internal to the tty port.
259 */
260
261void tty_port_raise_dtr_rts(struct tty_port *port)
262{
263    if (port->ops->dtr_rts)
264        port->ops->dtr_rts(port, 1);
265}
266EXPORT_SYMBOL(tty_port_raise_dtr_rts);
267
268/**
269 * tty_port_lower_dtr_rts - Lower DTR/RTS
270 * @port: tty port
271 *
272 * Wrapper for the DTR/RTS raise logic. For the moment this is used
273 * to hide some internal details. This will eventually become entirely
274 * internal to the tty port.
275 */
276
277void tty_port_lower_dtr_rts(struct tty_port *port)
278{
279    if (port->ops->dtr_rts)
280        port->ops->dtr_rts(port, 0);
281}
282EXPORT_SYMBOL(tty_port_lower_dtr_rts);
283
284/**
285 * tty_port_block_til_ready - Waiting logic for tty open
286 * @port: the tty port being opened
287 * @tty: the tty device being bound
288 * @filp: the file pointer of the opener
289 *
290 * Implement the core POSIX/SuS tty behaviour when opening a tty device.
291 * Handles:
292 * - hangup (both before and during)
293 * - non blocking open
294 * - rts/dtr/dcd
295 * - signals
296 * - port flags and counts
297 *
298 * The passed tty_port must implement the carrier_raised method if it can
299 * do carrier detect and the dtr_rts method if it supports software
300 * management of these lines. Note that the dtr/rts raise is done each
301 * iteration as a hangup may have previously dropped them while we wait.
302 */
303
304int tty_port_block_til_ready(struct tty_port *port,
305                struct tty_struct *tty, struct file *filp)
306{
307    int do_clocal = 0, retval;
308    unsigned long flags;
309    DEFINE_WAIT(wait);
310
311    /* block if port is in the process of being closed */
312    if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
313        wait_event_interruptible_tty(tty, port->close_wait,
314                !(port->flags & ASYNC_CLOSING));
315        if (port->flags & ASYNC_HUP_NOTIFY)
316            return -EAGAIN;
317        else
318            return -ERESTARTSYS;
319    }
320
321    /* if non-blocking mode is set we can pass directly to open unless
322       the port has just hung up or is in another error state */
323    if (tty->flags & (1 << TTY_IO_ERROR)) {
324        port->flags |= ASYNC_NORMAL_ACTIVE;
325        return 0;
326    }
327    if (filp->f_flags & O_NONBLOCK) {
328        /* Indicate we are open */
329        if (tty->termios.c_cflag & CBAUD)
330            tty_port_raise_dtr_rts(port);
331        port->flags |= ASYNC_NORMAL_ACTIVE;
332        return 0;
333    }
334
335    if (C_CLOCAL(tty))
336        do_clocal = 1;
337
338    /* Block waiting until we can proceed. We may need to wait for the
339       carrier, but we must also wait for any close that is in progress
340       before the next open may complete */
341
342    retval = 0;
343
344    /* The port lock protects the port counts */
345    spin_lock_irqsave(&port->lock, flags);
346    if (!tty_hung_up_p(filp))
347        port->count--;
348    port->blocked_open++;
349    spin_unlock_irqrestore(&port->lock, flags);
350
351    while (1) {
352        /* Indicate we are open */
353        if (tty->termios.c_cflag & CBAUD)
354            tty_port_raise_dtr_rts(port);
355
356        prepare_to_wait(&port->open_wait, &wait, TASK_INTERRUPTIBLE);
357        /* Check for a hangup or uninitialised port.
358                            Return accordingly */
359        if (tty_hung_up_p(filp) || !(port->flags & ASYNC_INITIALIZED)) {
360            if (port->flags & ASYNC_HUP_NOTIFY)
361                retval = -EAGAIN;
362            else
363                retval = -ERESTARTSYS;
364            break;
365        }
366        /*
367         * Probe the carrier. For devices with no carrier detect
368         * tty_port_carrier_raised will always return true.
369         * Never ask drivers if CLOCAL is set, this causes troubles
370         * on some hardware.
371         */
372        if (!(port->flags & ASYNC_CLOSING) &&
373                (do_clocal || tty_port_carrier_raised(port)))
374            break;
375        if (signal_pending(current)) {
376            retval = -ERESTARTSYS;
377            break;
378        }
379        tty_unlock(tty);
380        schedule();
381        tty_lock(tty);
382    }
383    finish_wait(&port->open_wait, &wait);
384
385    /* Update counts. A parallel hangup will have set count to zero and
386       we must not mess that up further */
387    spin_lock_irqsave(&port->lock, flags);
388    if (!tty_hung_up_p(filp))
389        port->count++;
390    port->blocked_open--;
391    if (retval == 0)
392        port->flags |= ASYNC_NORMAL_ACTIVE;
393    spin_unlock_irqrestore(&port->lock, flags);
394    return retval;
395}
396EXPORT_SYMBOL(tty_port_block_til_ready);
397
398int tty_port_close_start(struct tty_port *port,
399                struct tty_struct *tty, struct file *filp)
400{
401    unsigned long flags;
402
403    spin_lock_irqsave(&port->lock, flags);
404    if (tty_hung_up_p(filp)) {
405        spin_unlock_irqrestore(&port->lock, flags);
406        return 0;
407    }
408
409    if (tty->count == 1 && port->count != 1) {
410        printk(KERN_WARNING
411            "tty_port_close_start: tty->count = 1 port count = %d.\n",
412                                port->count);
413        port->count = 1;
414    }
415    if (--port->count < 0) {
416        printk(KERN_WARNING "tty_port_close_start: count = %d\n",
417                                port->count);
418        port->count = 0;
419    }
420
421    if (port->count) {
422        spin_unlock_irqrestore(&port->lock, flags);
423        if (port->ops->drop)
424            port->ops->drop(port);
425        return 0;
426    }
427    set_bit(ASYNCB_CLOSING, &port->flags);
428    tty->closing = 1;
429    spin_unlock_irqrestore(&port->lock, flags);
430    /* Don't block on a stalled port, just pull the chain */
431    if (tty->flow_stopped)
432        tty_driver_flush_buffer(tty);
433    if (test_bit(ASYNCB_INITIALIZED, &port->flags) &&
434            port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
435        tty_wait_until_sent_from_close(tty, port->closing_wait);
436    if (port->drain_delay) {
437        unsigned int bps = tty_get_baud_rate(tty);
438        long timeout;
439
440        if (bps > 1200)
441            timeout = max_t(long,
442                (HZ * 10 * port->drain_delay) / bps, HZ / 10);
443        else
444            timeout = 2 * HZ;
445        schedule_timeout_interruptible(timeout);
446    }
447    /* Flush the ldisc buffering */
448    tty_ldisc_flush(tty);
449
450    /* Drop DTR/RTS if HUPCL is set. This causes any attached modem to
451       hang up the line */
452    if (tty->termios.c_cflag & HUPCL)
453        tty_port_lower_dtr_rts(port);
454
455    /* Don't call port->drop for the last reference. Callers will want
456       to drop the last active reference in ->shutdown() or the tty
457       shutdown path */
458    return 1;
459}
460EXPORT_SYMBOL(tty_port_close_start);
461
462void tty_port_close_end(struct tty_port *port, struct tty_struct *tty)
463{
464    unsigned long flags;
465
466    spin_lock_irqsave(&port->lock, flags);
467    tty->closing = 0;
468
469    if (port->blocked_open) {
470        spin_unlock_irqrestore(&port->lock, flags);
471        if (port->close_delay) {
472            msleep_interruptible(
473                jiffies_to_msecs(port->close_delay));
474        }
475        spin_lock_irqsave(&port->lock, flags);
476        wake_up_interruptible(&port->open_wait);
477    }
478    port->flags &= ~(ASYNC_NORMAL_ACTIVE | ASYNC_CLOSING);
479    wake_up_interruptible(&port->close_wait);
480    spin_unlock_irqrestore(&port->lock, flags);
481}
482EXPORT_SYMBOL(tty_port_close_end);
483
484void tty_port_close(struct tty_port *port, struct tty_struct *tty,
485                            struct file *filp)
486{
487    if (tty_port_close_start(port, tty, filp) == 0)
488        return;
489    tty_port_shutdown(port);
490    set_bit(TTY_IO_ERROR, &tty->flags);
491    tty_port_close_end(port, tty);
492    tty_port_tty_set(port, NULL);
493}
494EXPORT_SYMBOL(tty_port_close);
495
496/**
497 * tty_port_install - generic tty->ops->install handler
498 * @port: tty_port of the device
499 * @driver: tty_driver for this device
500 * @tty: tty to be installed
501 *
502 * It is the same as tty_standard_install except the provided @port is linked
503 * to a concrete tty specified by @tty. Use this or tty_port_register_device
504 * (or both). Call tty_port_link_device as a last resort.
505 */
506int tty_port_install(struct tty_port *port, struct tty_driver *driver,
507        struct tty_struct *tty)
508{
509    tty->port = port;
510    return tty_standard_install(driver, tty);
511}
512EXPORT_SYMBOL_GPL(tty_port_install);
513
514int tty_port_open(struct tty_port *port, struct tty_struct *tty,
515                            struct file *filp)
516{
517    spin_lock_irq(&port->lock);
518    if (!tty_hung_up_p(filp))
519        ++port->count;
520    spin_unlock_irq(&port->lock);
521    tty_port_tty_set(port, tty);
522
523    /*
524     * Do the device-specific open only if the hardware isn't
525     * already initialized. Serialize open and shutdown using the
526     * port mutex.
527     */
528
529    mutex_lock(&port->mutex);
530
531    if (!test_bit(ASYNCB_INITIALIZED, &port->flags)) {
532        clear_bit(TTY_IO_ERROR, &tty->flags);
533        if (port->ops->activate) {
534            int retval = port->ops->activate(port, tty);
535            if (retval) {
536                mutex_unlock(&port->mutex);
537                return retval;
538            }
539        }
540        set_bit(ASYNCB_INITIALIZED, &port->flags);
541    }
542    mutex_unlock(&port->mutex);
543    return tty_port_block_til_ready(port, tty, filp);
544}
545
546EXPORT_SYMBOL(tty_port_open);
547

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