1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Tty port functions
4 */
5
6#include <linux/types.h>
7#include <linux/errno.h>
8#include <linux/tty.h>
9#include <linux/tty_driver.h>
10#include <linux/tty_flip.h>
11#include <linux/serial.h>
12#include <linux/timer.h>
13#include <linux/string.h>
14#include <linux/slab.h>
15#include <linux/sched/signal.h>
16#include <linux/wait.h>
17#include <linux/bitops.h>
18#include <linux/delay.h>
19#include <linux/module.h>
20#include <linux/serdev.h>
21
22static int tty_port_default_receive_buf(struct tty_port *port,
23 const unsigned char *p,
24 const unsigned char *f, size_t count)
25{
26 int ret;
27 struct tty_struct *tty;
28 struct tty_ldisc *disc;
29
30 tty = READ_ONCE(port->itty);
31 if (!tty)
32 return 0;
33
34 disc = tty_ldisc_ref(tty);
35 if (!disc)
36 return 0;
37
38 ret = tty_ldisc_receive_buf(disc, p, (char *)f, count);
39
40 tty_ldisc_deref(disc);
41
42 return ret;
43}
44
45static void tty_port_default_wakeup(struct tty_port *port)
46{
47 struct tty_struct *tty = tty_port_tty_get(port);
48
49 if (tty) {
50 tty_wakeup(tty);
51 tty_kref_put(tty);
52 }
53}
54
55static const struct tty_port_client_operations default_client_ops = {
56 .receive_buf = tty_port_default_receive_buf,
57 .write_wakeup = tty_port_default_wakeup,
58};
59
60void tty_port_init(struct tty_port *port)
61{
62 memset(port, 0, sizeof(*port));
63 tty_buffer_init(port);
64 init_waitqueue_head(&port->open_wait);
65 init_waitqueue_head(&port->delta_msr_wait);
66 mutex_init(&port->mutex);
67 mutex_init(&port->buf_mutex);
68 spin_lock_init(&port->lock);
69 port->close_delay = (50 * HZ) / 100;
70 port->closing_wait = (3000 * HZ) / 100;
71 port->client_ops = &default_client_ops;
72 kref_init(&port->kref);
73}
74EXPORT_SYMBOL(tty_port_init);
75
76/**
77 * tty_port_link_device - link tty and tty_port
78 * @port: tty_port of the device
79 * @driver: tty_driver for this device
80 * @index: index of the tty
81 *
82 * Provide the tty layer with a link from a tty (specified by @index) to a
83 * tty_port (@port). Use this only if neither tty_port_register_device nor
84 * tty_port_install is used in the driver. If used, this has to be called before
85 * tty_register_driver.
86 */
87void tty_port_link_device(struct tty_port *port,
88 struct tty_driver *driver, unsigned index)
89{
90 if (WARN_ON(index >= driver->num))
91 return;
92 driver->ports[index] = port;
93}
94EXPORT_SYMBOL_GPL(tty_port_link_device);
95
96/**
97 * tty_port_register_device - register tty device
98 * @port: tty_port of the device
99 * @driver: tty_driver for this device
100 * @index: index of the tty
101 * @device: parent if exists, otherwise NULL
102 *
103 * It is the same as tty_register_device except the provided @port is linked to
104 * a concrete tty specified by @index. Use this or tty_port_install (or both).
105 * Call tty_port_link_device as a last resort.
106 */
107struct device *tty_port_register_device(struct tty_port *port,
108 struct tty_driver *driver, unsigned index,
109 struct device *device)
110{
111 return tty_port_register_device_attr(port, driver, index, device, NULL, NULL);
112}
113EXPORT_SYMBOL_GPL(tty_port_register_device);
114
115/**
116 * tty_port_register_device_attr - register tty device
117 * @port: tty_port of the device
118 * @driver: tty_driver for this device
119 * @index: index of the tty
120 * @device: parent if exists, otherwise NULL
121 * @drvdata: Driver data to be set to device.
122 * @attr_grp: Attribute group to be set on device.
123 *
124 * It is the same as tty_register_device_attr except the provided @port is
125 * linked to a concrete tty specified by @index. Use this or tty_port_install
126 * (or both). Call tty_port_link_device as a last resort.
127 */
128struct device *tty_port_register_device_attr(struct tty_port *port,
129 struct tty_driver *driver, unsigned index,
130 struct device *device, void *drvdata,
131 const struct attribute_group **attr_grp)
132{
133 tty_port_link_device(port, driver, index);
134 return tty_register_device_attr(driver, index, device, drvdata,
135 attr_grp);
136}
137EXPORT_SYMBOL_GPL(tty_port_register_device_attr);
138
139/**
140 * tty_port_register_device_attr_serdev - register tty or serdev device
141 * @port: tty_port of the device
142 * @driver: tty_driver for this device
143 * @index: index of the tty
144 * @device: parent if exists, otherwise NULL
145 * @drvdata: driver data for the device
146 * @attr_grp: attribute group for the device
147 *
148 * Register a serdev or tty device depending on if the parent device has any
149 * defined serdev clients or not.
150 */
151struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
152 struct tty_driver *driver, unsigned index,
153 struct device *device, void *drvdata,
154 const struct attribute_group **attr_grp)
155{
156 struct device *dev;
157
158 tty_port_link_device(port, driver, index);
159
160 dev = serdev_tty_port_register(port, device, driver, index);
161 if (PTR_ERR(dev) != -ENODEV) {
162 /* Skip creating cdev if we registered a serdev device */
163 return dev;
164 }
165
166 return tty_register_device_attr(driver, index, device, drvdata,
167 attr_grp);
168}
169EXPORT_SYMBOL_GPL(tty_port_register_device_attr_serdev);
170
171/**
172 * tty_port_register_device_serdev - register tty or serdev device
173 * @port: tty_port of the device
174 * @driver: tty_driver for this device
175 * @index: index of the tty
176 * @device: parent if exists, otherwise NULL
177 *
178 * Register a serdev or tty device depending on if the parent device has any
179 * defined serdev clients or not.
180 */
181struct device *tty_port_register_device_serdev(struct tty_port *port,
182 struct tty_driver *driver, unsigned index,
183 struct device *device)
184{
185 return tty_port_register_device_attr_serdev(port, driver, index,
186 device, NULL, NULL);
187}
188EXPORT_SYMBOL_GPL(tty_port_register_device_serdev);
189
190/**
191 * tty_port_unregister_device - deregister a tty or serdev device
192 * @port: tty_port of the device
193 * @driver: tty_driver for this device
194 * @index: index of the tty
195 *
196 * If a tty or serdev device is registered with a call to
197 * tty_port_register_device_serdev() then this function must be called when
198 * the device is gone.
199 */
200void tty_port_unregister_device(struct tty_port *port,
201 struct tty_driver *driver, unsigned index)
202{
203 int ret;
204
205 ret = serdev_tty_port_unregister(port);
206 if (ret == 0)
207 return;
208
209 tty_unregister_device(driver, index);
210}
211EXPORT_SYMBOL_GPL(tty_port_unregister_device);
212
213int tty_port_alloc_xmit_buf(struct tty_port *port)
214{
215 /* We may sleep in get_zeroed_page() */
216 mutex_lock(&port->buf_mutex);
217 if (port->xmit_buf == NULL)
218 port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
219 mutex_unlock(&port->buf_mutex);
220 if (port->xmit_buf == NULL)
221 return -ENOMEM;
222 return 0;
223}
224EXPORT_SYMBOL(tty_port_alloc_xmit_buf);
225
226void tty_port_free_xmit_buf(struct tty_port *port)
227{
228 mutex_lock(&port->buf_mutex);
229 if (port->xmit_buf != NULL) {
230 free_page((unsigned long)port->xmit_buf);
231 port->xmit_buf = NULL;
232 }
233 mutex_unlock(&port->buf_mutex);
234}
235EXPORT_SYMBOL(tty_port_free_xmit_buf);
236
237/**
238 * tty_port_destroy -- destroy inited port
239 * @port: tty port to be destroyed
240 *
241 * When a port was initialized using tty_port_init, one has to destroy the
242 * port by this function. Either indirectly by using tty_port refcounting
243 * (tty_port_put) or directly if refcounting is not used.
244 */
245void tty_port_destroy(struct tty_port *port)
246{
247 tty_buffer_cancel_work(port);
248 tty_buffer_free_all(port);
249}
250EXPORT_SYMBOL(tty_port_destroy);
251
252static void tty_port_destructor(struct kref *kref)
253{
254 struct tty_port *port = container_of(kref, struct tty_port, kref);
255
256 /* check if last port ref was dropped before tty release */
257 if (WARN_ON(port->itty))
258 return;
259 if (port->xmit_buf)
260 free_page((unsigned long)port->xmit_buf);
261 tty_port_destroy(port);
262 if (port->ops && port->ops->destruct)
263 port->ops->destruct(port);
264 else
265 kfree(port);
266}
267
268void tty_port_put(struct tty_port *port)
269{
270 if (port)
271 kref_put(&port->kref, tty_port_destructor);
272}
273EXPORT_SYMBOL(tty_port_put);
274
275/**
276 * tty_port_tty_get - get a tty reference
277 * @port: tty port
278 *
279 * Return a refcount protected tty instance or NULL if the port is not
280 * associated with a tty (eg due to close or hangup)
281 */
282struct tty_struct *tty_port_tty_get(struct tty_port *port)
283{
284 unsigned long flags;
285 struct tty_struct *tty;
286
287 spin_lock_irqsave(&port->lock, flags);
288 tty = tty_kref_get(port->tty);
289 spin_unlock_irqrestore(&port->lock, flags);
290 return tty;
291}
292EXPORT_SYMBOL(tty_port_tty_get);
293
294/**
295 * tty_port_tty_set - set the tty of a port
296 * @port: tty port
297 * @tty: the tty
298 *
299 * Associate the port and tty pair. Manages any internal refcounts.
300 * Pass NULL to deassociate a port
301 */
302void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty)
303{
304 unsigned long flags;
305
306 spin_lock_irqsave(&port->lock, flags);
307 tty_kref_put(port->tty);
308 port->tty = tty_kref_get(tty);
309 spin_unlock_irqrestore(&port->lock, flags);
310}
311EXPORT_SYMBOL(tty_port_tty_set);
312
313static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty)
314{
315 mutex_lock(&port->mutex);
316 if (port->console)
317 goto out;
318
319 if (tty_port_initialized(port)) {
320 tty_port_set_initialized(port, 0);
321 /*
322 * Drop DTR/RTS if HUPCL is set. This causes any attached
323 * modem to hang up the line.
324 */
325 if (tty && C_HUPCL(tty))
326 tty_port_lower_dtr_rts(port);
327
328 if (port->ops->shutdown)
329 port->ops->shutdown(port);
330 }
331out:
332 mutex_unlock(&port->mutex);
333}
334
335/**
336 * tty_port_hangup - hangup helper
337 * @port: tty port
338 *
339 * Perform port level tty hangup flag and count changes. Drop the tty
340 * reference.
341 *
342 * Caller holds tty lock.
343 */
344void tty_port_hangup(struct tty_port *port)
345{
346 struct tty_struct *tty;
347 unsigned long flags;
348
349 spin_lock_irqsave(&port->lock, flags);
350 port->count = 0;
351 tty = port->tty;
352 if (tty)
353 set_bit(TTY_IO_ERROR, &tty->flags);
354 port->tty = NULL;
355 spin_unlock_irqrestore(&port->lock, flags);
356 tty_port_set_active(port, 0);
357 tty_port_shutdown(port, tty);
358 tty_kref_put(tty);
359 wake_up_interruptible(&port->open_wait);
360 wake_up_interruptible(&port->delta_msr_wait);
361}
362EXPORT_SYMBOL(tty_port_hangup);
363
364/**
365 * tty_port_tty_hangup - helper to hang up a tty
366 *
367 * @port: tty port
368 * @check_clocal: hang only ttys with CLOCAL unset?
369 */
370void tty_port_tty_hangup(struct tty_port *port, bool check_clocal)
371{
372 struct tty_struct *tty = tty_port_tty_get(port);
373
374 if (tty && (!check_clocal || !C_CLOCAL(tty)))
375 tty_hangup(tty);
376 tty_kref_put(tty);
377}
378EXPORT_SYMBOL_GPL(tty_port_tty_hangup);
379
380/**
381 * tty_port_tty_wakeup - helper to wake up a tty
382 *
383 * @port: tty port
384 */
385void tty_port_tty_wakeup(struct tty_port *port)
386{
387 port->client_ops->write_wakeup(port);
388}
389EXPORT_SYMBOL_GPL(tty_port_tty_wakeup);
390
391/**
392 * tty_port_carrier_raised - carrier raised check
393 * @port: tty port
394 *
395 * Wrapper for the carrier detect logic. For the moment this is used
396 * to hide some internal details. This will eventually become entirely
397 * internal to the tty port.
398 */
399int tty_port_carrier_raised(struct tty_port *port)
400{
401 if (port->ops->carrier_raised == NULL)
402 return 1;
403 return port->ops->carrier_raised(port);
404}
405EXPORT_SYMBOL(tty_port_carrier_raised);
406
407/**
408 * tty_port_raise_dtr_rts - Raise DTR/RTS
409 * @port: tty port
410 *
411 * Wrapper for the DTR/RTS raise logic. For the moment this is used
412 * to hide some internal details. This will eventually become entirely
413 * internal to the tty port.
414 */
415void tty_port_raise_dtr_rts(struct tty_port *port)
416{
417 if (port->ops->dtr_rts)
418 port->ops->dtr_rts(port, 1);
419}
420EXPORT_SYMBOL(tty_port_raise_dtr_rts);
421
422/**
423 * tty_port_lower_dtr_rts - Lower DTR/RTS
424 * @port: tty port
425 *
426 * Wrapper for the DTR/RTS raise logic. For the moment this is used
427 * to hide some internal details. This will eventually become entirely
428 * internal to the tty port.
429 */
430void tty_port_lower_dtr_rts(struct tty_port *port)
431{
432 if (port->ops->dtr_rts)
433 port->ops->dtr_rts(port, 0);
434}
435EXPORT_SYMBOL(tty_port_lower_dtr_rts);
436
437/**
438 * tty_port_block_til_ready - Waiting logic for tty open
439 * @port: the tty port being opened
440 * @tty: the tty device being bound
441 * @filp: the file pointer of the opener or NULL
442 *
443 * Implement the core POSIX/SuS tty behaviour when opening a tty device.
444 * Handles:
445 * - hangup (both before and during)
446 * - non blocking open
447 * - rts/dtr/dcd
448 * - signals
449 * - port flags and counts
450 *
451 * The passed tty_port must implement the carrier_raised method if it can
452 * do carrier detect and the dtr_rts method if it supports software
453 * management of these lines. Note that the dtr/rts raise is done each
454 * iteration as a hangup may have previously dropped them while we wait.
455 *
456 * Caller holds tty lock.
457 *
458 * NB: May drop and reacquire tty lock when blocking, so tty and tty_port
459 * may have changed state (eg., may have been hung up).
460 */
461int tty_port_block_til_ready(struct tty_port *port,
462 struct tty_struct *tty, struct file *filp)
463{
464 int do_clocal = 0, retval;
465 unsigned long flags;
466 DEFINE_WAIT(wait);
467
468 /* if non-blocking mode is set we can pass directly to open unless
469 the port has just hung up or is in another error state */
470 if (tty_io_error(tty)) {
471 tty_port_set_active(port, 1);
472 return 0;
473 }
474 if (filp == NULL || (filp->f_flags & O_NONBLOCK)) {
475 /* Indicate we are open */
476 if (C_BAUD(tty))
477 tty_port_raise_dtr_rts(port);
478 tty_port_set_active(port, 1);
479 return 0;
480 }
481
482 if (C_CLOCAL(tty))
483 do_clocal = 1;
484
485 /* Block waiting until we can proceed. We may need to wait for the
486 carrier, but we must also wait for any close that is in progress
487 before the next open may complete */
488
489 retval = 0;
490
491 /* The port lock protects the port counts */
492 spin_lock_irqsave(&port->lock, flags);
493 port->count--;
494 port->blocked_open++;
495 spin_unlock_irqrestore(&port->lock, flags);
496
497 while (1) {
498 /* Indicate we are open */
499 if (C_BAUD(tty) && tty_port_initialized(port))
500 tty_port_raise_dtr_rts(port);
501
502 prepare_to_wait(&port->open_wait, &wait, TASK_INTERRUPTIBLE);
503 /* Check for a hangup or uninitialised port.
504 Return accordingly */
505 if (tty_hung_up_p(filp) || !tty_port_initialized(port)) {
506 if (port->flags & ASYNC_HUP_NOTIFY)
507 retval = -EAGAIN;
508 else
509 retval = -ERESTARTSYS;
510 break;
511 }
512 /*
513 * Probe the carrier. For devices with no carrier detect
514 * tty_port_carrier_raised will always return true.
515 * Never ask drivers if CLOCAL is set, this causes troubles
516 * on some hardware.
517 */
518 if (do_clocal || tty_port_carrier_raised(port))
519 break;
520 if (signal_pending(current)) {
521 retval = -ERESTARTSYS;
522 break;
523 }
524 tty_unlock(tty);
525 schedule();
526 tty_lock(tty);
527 }
528 finish_wait(&port->open_wait, &wait);
529
530 /* Update counts. A parallel hangup will have set count to zero and
531 we must not mess that up further */
532 spin_lock_irqsave(&port->lock, flags);
533 if (!tty_hung_up_p(filp))
534 port->count++;
535 port->blocked_open--;
536 spin_unlock_irqrestore(&port->lock, flags);
537 if (retval == 0)
538 tty_port_set_active(port, 1);
539 return retval;
540}
541EXPORT_SYMBOL(tty_port_block_til_ready);
542
543static void tty_port_drain_delay(struct tty_port *port, struct tty_struct *tty)
544{
545 unsigned int bps = tty_get_baud_rate(tty);
546 long timeout;
547
548 if (bps > 1200) {
549 timeout = (HZ * 10 * port->drain_delay) / bps;
550 timeout = max_t(long, timeout, HZ / 10);
551 } else {
552 timeout = 2 * HZ;
553 }
554 schedule_timeout_interruptible(timeout);
555}
556
557/* Caller holds tty lock. */
558int tty_port_close_start(struct tty_port *port,
559 struct tty_struct *tty, struct file *filp)
560{
561 unsigned long flags;
562
563 if (tty_hung_up_p(filp))
564 return 0;
565
566 spin_lock_irqsave(&port->lock, flags);
567 if (tty->count == 1 && port->count != 1) {
568 tty_warn(tty, "%s: tty->count = 1 port count = %d\n", __func__,
569 port->count);
570 port->count = 1;
571 }
572 if (--port->count < 0) {
573 tty_warn(tty, "%s: bad port count (%d)\n", __func__,
574 port->count);
575 port->count = 0;
576 }
577
578 if (port->count) {
579 spin_unlock_irqrestore(&port->lock, flags);
580 return 0;
581 }
582 spin_unlock_irqrestore(&port->lock, flags);
583
584 tty->closing = 1;
585
586 if (tty_port_initialized(port)) {
587 /* Don't block on a stalled port, just pull the chain */
588 if (tty->flow_stopped)
589 tty_driver_flush_buffer(tty);
590 if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
591 tty_wait_until_sent(tty, port->closing_wait);
592 if (port->drain_delay)
593 tty_port_drain_delay(port, tty);
594 }
595 /* Flush the ldisc buffering */
596 tty_ldisc_flush(tty);
597
598 /* Report to caller this is the last port reference */
599 return 1;
600}
601EXPORT_SYMBOL(tty_port_close_start);
602
603/* Caller holds tty lock */
604void tty_port_close_end(struct tty_port *port, struct tty_struct *tty)
605{
606 unsigned long flags;
607
608 tty_ldisc_flush(tty);
609 tty->closing = 0;
610
611 spin_lock_irqsave(&port->lock, flags);
612
613 if (port->blocked_open) {
614 spin_unlock_irqrestore(&port->lock, flags);
615 if (port->close_delay)
616 msleep_interruptible(jiffies_to_msecs(port->close_delay));
617 spin_lock_irqsave(&port->lock, flags);
618 wake_up_interruptible(&port->open_wait);
619 }
620 spin_unlock_irqrestore(&port->lock, flags);
621 tty_port_set_active(port, 0);
622}
623EXPORT_SYMBOL(tty_port_close_end);
624
625/**
626 * tty_port_close
627 *
628 * Caller holds tty lock
629 */
630void tty_port_close(struct tty_port *port, struct tty_struct *tty,
631 struct file *filp)
632{
633 if (tty_port_close_start(port, tty, filp) == 0)
634 return;
635 tty_port_shutdown(port, tty);
636 if (!port->console)
637 set_bit(TTY_IO_ERROR, &tty->flags);
638 tty_port_close_end(port, tty);
639 tty_port_tty_set(port, NULL);
640}
641EXPORT_SYMBOL(tty_port_close);
642
643/**
644 * tty_port_install - generic tty->ops->install handler
645 * @port: tty_port of the device
646 * @driver: tty_driver for this device
647 * @tty: tty to be installed
648 *
649 * It is the same as tty_standard_install except the provided @port is linked
650 * to a concrete tty specified by @tty. Use this or tty_port_register_device
651 * (or both). Call tty_port_link_device as a last resort.
652 */
653int tty_port_install(struct tty_port *port, struct tty_driver *driver,
654 struct tty_struct *tty)
655{
656 tty->port = port;
657 return tty_standard_install(driver, tty);
658}
659EXPORT_SYMBOL_GPL(tty_port_install);
660
661/**
662 * tty_port_open
663 *
664 * Caller holds tty lock.
665 *
666 * NB: may drop and reacquire tty lock (in tty_port_block_til_ready()) so
667 * tty and tty_port may have changed state (eg., may be hung up now)
668 */
669int tty_port_open(struct tty_port *port, struct tty_struct *tty,
670 struct file *filp)
671{
672 spin_lock_irq(&port->lock);
673 ++port->count;
674 spin_unlock_irq(&port->lock);
675 tty_port_tty_set(port, tty);
676
677 /*
678 * Do the device-specific open only if the hardware isn't
679 * already initialized. Serialize open and shutdown using the
680 * port mutex.
681 */
682
683 mutex_lock(&port->mutex);
684
685 if (!tty_port_initialized(port)) {
686 clear_bit(TTY_IO_ERROR, &tty->flags);
687 if (port->ops->activate) {
688 int retval = port->ops->activate(port, tty);
689 if (retval) {
690 mutex_unlock(&port->mutex);
691 return retval;
692 }
693 }
694 tty_port_set_initialized(port, 1);
695 }
696 mutex_unlock(&port->mutex);
697 return tty_port_block_til_ready(port, tty, filp);
698}
699
700EXPORT_SYMBOL(tty_port_open);
701