hvc_console: Improve tty/console put_chars handling
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / tty / hvc / hvc_console.c
blob59000750cc73819e9bf6c5bf0dd80757aa247d86
1 /*
2 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
3 * Copyright (C) 2001 Paul Mackerras <paulus@au.ibm.com>, IBM
4 * Copyright (C) 2004 Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp.
5 * Copyright (C) 2004 IBM Corporation
7 * Additional Author(s):
8 * Ryan S. Arnold <rsa@us.ibm.com>
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
25 #include <linux/console.h>
26 #include <linux/cpumask.h>
27 #include <linux/init.h>
28 #include <linux/kbd_kern.h>
29 #include <linux/kernel.h>
30 #include <linux/kthread.h>
31 #include <linux/list.h>
32 #include <linux/module.h>
33 #include <linux/major.h>
34 #include <linux/sysrq.h>
35 #include <linux/tty.h>
36 #include <linux/tty_flip.h>
37 #include <linux/sched.h>
38 #include <linux/spinlock.h>
39 #include <linux/delay.h>
40 #include <linux/freezer.h>
41 #include <linux/slab.h>
43 #include <asm/uaccess.h>
45 #include "hvc_console.h"
47 #define HVC_MAJOR 229
48 #define HVC_MINOR 0
51 * Wait this long per iteration while trying to push buffered data to the
52 * hypervisor before allowing the tty to complete a close operation.
54 #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
57 * These sizes are most efficient for vio, because they are the
58 * native transfer size. We could make them selectable in the
59 * future to better deal with backends that want other buffer sizes.
61 #define N_OUTBUF 16
62 #define N_INBUF 16
64 #define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
66 static struct tty_driver *hvc_driver;
67 static struct task_struct *hvc_task;
69 /* Picks up late kicks after list walk but before schedule() */
70 static int hvc_kicked;
72 static int hvc_init(void);
74 #ifdef CONFIG_MAGIC_SYSRQ
75 static int sysrq_pressed;
76 #endif
78 /* dynamic list of hvc_struct instances */
79 static LIST_HEAD(hvc_structs);
82 * Protect the list of hvc_struct instances from inserts and removals during
83 * list traversal.
85 static DEFINE_SPINLOCK(hvc_structs_lock);
88 * This value is used to assign a tty->index value to a hvc_struct based
89 * upon order of exposure via hvc_probe(), when we can not match it to
90 * a console candidate registered with hvc_instantiate().
92 static int last_hvc = -1;
95 * Do not call this function with either the hvc_structs_lock or the hvc_struct
96 * lock held. If successful, this function increments the kref reference
97 * count against the target hvc_struct so it should be released when finished.
99 static struct hvc_struct *hvc_get_by_index(int index)
101 struct hvc_struct *hp;
102 unsigned long flags;
104 spin_lock(&hvc_structs_lock);
106 list_for_each_entry(hp, &hvc_structs, next) {
107 spin_lock_irqsave(&hp->lock, flags);
108 if (hp->index == index) {
109 kref_get(&hp->kref);
110 spin_unlock_irqrestore(&hp->lock, flags);
111 spin_unlock(&hvc_structs_lock);
112 return hp;
114 spin_unlock_irqrestore(&hp->lock, flags);
116 hp = NULL;
118 spin_unlock(&hvc_structs_lock);
119 return hp;
124 * Initial console vtermnos for console API usage prior to full console
125 * initialization. Any vty adapter outside this range will not have usable
126 * console interfaces but can still be used as a tty device. This has to be
127 * static because kmalloc will not work during early console init.
129 static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
130 static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
131 {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
134 * Console APIs, NOT TTY. These APIs are available immediately when
135 * hvc_console_setup() finds adapters.
138 static void hvc_console_print(struct console *co, const char *b,
139 unsigned count)
141 char c[N_OUTBUF] __ALIGNED__;
142 unsigned i = 0, n = 0;
143 int r, donecr = 0, index = co->index;
145 /* Console access attempt outside of acceptable console range. */
146 if (index >= MAX_NR_HVC_CONSOLES)
147 return;
149 /* This console adapter was removed so it is not usable. */
150 if (vtermnos[index] == -1)
151 return;
153 while (count > 0 || i > 0) {
154 if (count > 0 && i < sizeof(c)) {
155 if (b[n] == '\n' && !donecr) {
156 c[i++] = '\r';
157 donecr = 1;
158 } else {
159 c[i++] = b[n++];
160 donecr = 0;
161 --count;
163 } else {
164 r = cons_ops[index]->put_chars(vtermnos[index], c, i);
165 if (r <= 0) {
166 /* throw away characters on error
167 * but spin in case of -EAGAIN */
168 if (r != -EAGAIN)
169 i = 0;
170 } else if (r > 0) {
171 i -= r;
172 if (i > 0)
173 memmove(c, c+r, i);
179 static struct tty_driver *hvc_console_device(struct console *c, int *index)
181 if (vtermnos[c->index] == -1)
182 return NULL;
184 *index = c->index;
185 return hvc_driver;
188 static int __init hvc_console_setup(struct console *co, char *options)
190 if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
191 return -ENODEV;
193 if (vtermnos[co->index] == -1)
194 return -ENODEV;
196 return 0;
199 static struct console hvc_console = {
200 .name = "hvc",
201 .write = hvc_console_print,
202 .device = hvc_console_device,
203 .setup = hvc_console_setup,
204 .flags = CON_PRINTBUFFER,
205 .index = -1,
209 * Early console initialization. Precedes driver initialization.
211 * (1) we are first, and the user specified another driver
212 * -- index will remain -1
213 * (2) we are first and the user specified no driver
214 * -- index will be set to 0, then we will fail setup.
215 * (3) we are first and the user specified our driver
216 * -- index will be set to user specified driver, and we will fail
217 * (4) we are after driver, and this initcall will register us
218 * -- if the user didn't specify a driver then the console will match
220 * Note that for cases 2 and 3, we will match later when the io driver
221 * calls hvc_instantiate() and call register again.
223 static int __init hvc_console_init(void)
225 register_console(&hvc_console);
226 return 0;
228 console_initcall(hvc_console_init);
230 /* callback when the kboject ref count reaches zero. */
231 static void destroy_hvc_struct(struct kref *kref)
233 struct hvc_struct *hp = container_of(kref, struct hvc_struct, kref);
234 unsigned long flags;
236 spin_lock(&hvc_structs_lock);
238 spin_lock_irqsave(&hp->lock, flags);
239 list_del(&(hp->next));
240 spin_unlock_irqrestore(&hp->lock, flags);
242 spin_unlock(&hvc_structs_lock);
244 kfree(hp);
248 * hvc_instantiate() is an early console discovery method which locates
249 * consoles * prior to the vio subsystem discovering them. Hotplugged
250 * vty adapters do NOT get an hvc_instantiate() callback since they
251 * appear after early console init.
253 int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
255 struct hvc_struct *hp;
257 if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
258 return -1;
260 if (vtermnos[index] != -1)
261 return -1;
263 /* make sure no no tty has been registered in this index */
264 hp = hvc_get_by_index(index);
265 if (hp) {
266 kref_put(&hp->kref, destroy_hvc_struct);
267 return -1;
270 vtermnos[index] = vtermno;
271 cons_ops[index] = ops;
273 /* reserve all indices up to and including this index */
274 if (last_hvc < index)
275 last_hvc = index;
277 /* if this index is what the user requested, then register
278 * now (setup won't fail at this point). It's ok to just
279 * call register again if previously .setup failed.
281 if (index == hvc_console.index)
282 register_console(&hvc_console);
284 return 0;
286 EXPORT_SYMBOL_GPL(hvc_instantiate);
288 /* Wake the sleeping khvcd */
289 void hvc_kick(void)
291 hvc_kicked = 1;
292 wake_up_process(hvc_task);
294 EXPORT_SYMBOL_GPL(hvc_kick);
296 static void hvc_unthrottle(struct tty_struct *tty)
298 hvc_kick();
302 * The TTY interface won't be used until after the vio layer has exposed the vty
303 * adapter to the kernel.
305 static int hvc_open(struct tty_struct *tty, struct file * filp)
307 struct hvc_struct *hp;
308 unsigned long flags;
309 int rc = 0;
311 /* Auto increments kref reference if found. */
312 if (!(hp = hvc_get_by_index(tty->index)))
313 return -ENODEV;
315 spin_lock_irqsave(&hp->lock, flags);
316 /* Check and then increment for fast path open. */
317 if (hp->count++ > 0) {
318 tty_kref_get(tty);
319 spin_unlock_irqrestore(&hp->lock, flags);
320 hvc_kick();
321 return 0;
322 } /* else count == 0 */
324 tty->driver_data = hp;
326 hp->tty = tty_kref_get(tty);
328 spin_unlock_irqrestore(&hp->lock, flags);
330 if (hp->ops->notifier_add)
331 rc = hp->ops->notifier_add(hp, hp->data);
334 * If the notifier fails we return an error. The tty layer
335 * will call hvc_close() after a failed open but we don't want to clean
336 * up there so we'll clean up here and clear out the previously set
337 * tty fields and return the kref reference.
339 if (rc) {
340 spin_lock_irqsave(&hp->lock, flags);
341 hp->tty = NULL;
342 spin_unlock_irqrestore(&hp->lock, flags);
343 tty_kref_put(tty);
344 tty->driver_data = NULL;
345 kref_put(&hp->kref, destroy_hvc_struct);
346 printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
348 /* Force wakeup of the polling thread */
349 hvc_kick();
351 return rc;
354 static void hvc_close(struct tty_struct *tty, struct file * filp)
356 struct hvc_struct *hp;
357 unsigned long flags;
359 if (tty_hung_up_p(filp))
360 return;
363 * No driver_data means that this close was issued after a failed
364 * hvc_open by the tty layer's release_dev() function and we can just
365 * exit cleanly because the kref reference wasn't made.
367 if (!tty->driver_data)
368 return;
370 hp = tty->driver_data;
372 spin_lock_irqsave(&hp->lock, flags);
374 if (--hp->count == 0) {
375 /* We are done with the tty pointer now. */
376 hp->tty = NULL;
377 spin_unlock_irqrestore(&hp->lock, flags);
379 if (hp->ops->notifier_del)
380 hp->ops->notifier_del(hp, hp->data);
382 /* cancel pending tty resize work */
383 cancel_work_sync(&hp->tty_resize);
386 * Chain calls chars_in_buffer() and returns immediately if
387 * there is no buffered data otherwise sleeps on a wait queue
388 * waking periodically to check chars_in_buffer().
390 tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
391 } else {
392 if (hp->count < 0)
393 printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
394 hp->vtermno, hp->count);
395 spin_unlock_irqrestore(&hp->lock, flags);
398 tty_kref_put(tty);
399 kref_put(&hp->kref, destroy_hvc_struct);
402 static void hvc_hangup(struct tty_struct *tty)
404 struct hvc_struct *hp = tty->driver_data;
405 unsigned long flags;
406 int temp_open_count;
408 if (!hp)
409 return;
411 /* cancel pending tty resize work */
412 cancel_work_sync(&hp->tty_resize);
414 spin_lock_irqsave(&hp->lock, flags);
417 * The N_TTY line discipline has problems such that in a close vs
418 * open->hangup case this can be called after the final close so prevent
419 * that from happening for now.
421 if (hp->count <= 0) {
422 spin_unlock_irqrestore(&hp->lock, flags);
423 return;
426 temp_open_count = hp->count;
427 hp->count = 0;
428 hp->n_outbuf = 0;
429 hp->tty = NULL;
431 spin_unlock_irqrestore(&hp->lock, flags);
433 if (hp->ops->notifier_hangup)
434 hp->ops->notifier_hangup(hp, hp->data);
436 while(temp_open_count) {
437 --temp_open_count;
438 tty_kref_put(tty);
439 kref_put(&hp->kref, destroy_hvc_struct);
444 * Push buffered characters whether they were just recently buffered or waiting
445 * on a blocked hypervisor. Call this function with hp->lock held.
447 static int hvc_push(struct hvc_struct *hp)
449 int n;
451 n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
452 if (n <= 0) {
453 if (n == 0 || n == -EAGAIN) {
454 hp->do_wakeup = 1;
455 return 0;
457 /* throw away output on error; this happens when
458 there is no session connected to the vterm. */
459 hp->n_outbuf = 0;
460 } else
461 hp->n_outbuf -= n;
462 if (hp->n_outbuf > 0)
463 memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
464 else
465 hp->do_wakeup = 1;
467 return n;
470 static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
472 struct hvc_struct *hp = tty->driver_data;
473 unsigned long flags;
474 int rsize, written = 0;
476 /* This write was probably executed during a tty close. */
477 if (!hp)
478 return -EPIPE;
480 if (hp->count <= 0)
481 return -EIO;
483 spin_lock_irqsave(&hp->lock, flags);
485 /* Push pending writes */
486 if (hp->n_outbuf > 0)
487 hvc_push(hp);
489 while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
490 if (rsize > count)
491 rsize = count;
492 memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
493 count -= rsize;
494 buf += rsize;
495 hp->n_outbuf += rsize;
496 written += rsize;
497 hvc_push(hp);
499 spin_unlock_irqrestore(&hp->lock, flags);
502 * Racy, but harmless, kick thread if there is still pending data.
504 if (hp->n_outbuf)
505 hvc_kick();
507 return written;
511 * hvc_set_winsz() - Resize the hvc tty terminal window.
512 * @work: work structure.
514 * The routine shall not be called within an atomic context because it
515 * might sleep.
517 * Locking: hp->lock
519 static void hvc_set_winsz(struct work_struct *work)
521 struct hvc_struct *hp;
522 unsigned long hvc_flags;
523 struct tty_struct *tty;
524 struct winsize ws;
526 hp = container_of(work, struct hvc_struct, tty_resize);
528 spin_lock_irqsave(&hp->lock, hvc_flags);
529 if (!hp->tty) {
530 spin_unlock_irqrestore(&hp->lock, hvc_flags);
531 return;
533 ws = hp->ws;
534 tty = tty_kref_get(hp->tty);
535 spin_unlock_irqrestore(&hp->lock, hvc_flags);
537 tty_do_resize(tty, &ws);
538 tty_kref_put(tty);
542 * This is actually a contract between the driver and the tty layer outlining
543 * how much write room the driver can guarantee will be sent OR BUFFERED. This
544 * driver MUST honor the return value.
546 static int hvc_write_room(struct tty_struct *tty)
548 struct hvc_struct *hp = tty->driver_data;
550 if (!hp)
551 return -1;
553 return hp->outbuf_size - hp->n_outbuf;
556 static int hvc_chars_in_buffer(struct tty_struct *tty)
558 struct hvc_struct *hp = tty->driver_data;
560 if (!hp)
561 return 0;
562 return hp->n_outbuf;
566 * timeout will vary between the MIN and MAX values defined here. By default
567 * and during console activity we will use a default MIN_TIMEOUT of 10. When
568 * the console is idle, we increase the timeout value on each pass through
569 * msleep until we reach the max. This may be noticeable as a brief (average
570 * one second) delay on the console before the console responds to input when
571 * there has been no input for some time.
573 #define MIN_TIMEOUT (10)
574 #define MAX_TIMEOUT (2000)
575 static u32 timeout = MIN_TIMEOUT;
577 #define HVC_POLL_READ 0x00000001
578 #define HVC_POLL_WRITE 0x00000002
580 int hvc_poll(struct hvc_struct *hp)
582 struct tty_struct *tty;
583 int i, n, poll_mask = 0;
584 char buf[N_INBUF] __ALIGNED__;
585 unsigned long flags;
586 int read_total = 0;
587 int written_total = 0;
589 spin_lock_irqsave(&hp->lock, flags);
591 /* Push pending writes */
592 if (hp->n_outbuf > 0)
593 written_total = hvc_push(hp);
595 /* Reschedule us if still some write pending */
596 if (hp->n_outbuf > 0) {
597 poll_mask |= HVC_POLL_WRITE;
598 /* If hvc_push() was not able to write, sleep a few msecs */
599 timeout = (written_total) ? 0 : MIN_TIMEOUT;
602 /* No tty attached, just skip */
603 tty = tty_kref_get(hp->tty);
604 if (tty == NULL)
605 goto bail;
607 /* Now check if we can get data (are we throttled ?) */
608 if (test_bit(TTY_THROTTLED, &tty->flags))
609 goto throttled;
611 /* If we aren't notifier driven and aren't throttled, we always
612 * request a reschedule
614 if (!hp->irq_requested)
615 poll_mask |= HVC_POLL_READ;
617 /* Read data if any */
618 for (;;) {
619 int count = tty_buffer_request_room(tty, N_INBUF);
621 /* If flip is full, just reschedule a later read */
622 if (count == 0) {
623 poll_mask |= HVC_POLL_READ;
624 break;
627 n = hp->ops->get_chars(hp->vtermno, buf, count);
628 if (n <= 0) {
629 /* Hangup the tty when disconnected from host */
630 if (n == -EPIPE) {
631 spin_unlock_irqrestore(&hp->lock, flags);
632 tty_hangup(tty);
633 spin_lock_irqsave(&hp->lock, flags);
634 } else if ( n == -EAGAIN ) {
636 * Some back-ends can only ensure a certain min
637 * num of bytes read, which may be > 'count'.
638 * Let the tty clear the flip buff to make room.
640 poll_mask |= HVC_POLL_READ;
642 break;
644 for (i = 0; i < n; ++i) {
645 #ifdef CONFIG_MAGIC_SYSRQ
646 if (hp->index == hvc_console.index) {
647 /* Handle the SysRq Hack */
648 /* XXX should support a sequence */
649 if (buf[i] == '\x0f') { /* ^O */
650 /* if ^O is pressed again, reset
651 * sysrq_pressed and flip ^O char */
652 sysrq_pressed = !sysrq_pressed;
653 if (sysrq_pressed)
654 continue;
655 } else if (sysrq_pressed) {
656 handle_sysrq(buf[i]);
657 sysrq_pressed = 0;
658 continue;
661 #endif /* CONFIG_MAGIC_SYSRQ */
662 tty_insert_flip_char(tty, buf[i], 0);
665 read_total += n;
667 throttled:
668 /* Wakeup write queue if necessary */
669 if (hp->do_wakeup) {
670 hp->do_wakeup = 0;
671 tty_wakeup(tty);
673 bail:
674 spin_unlock_irqrestore(&hp->lock, flags);
676 if (read_total) {
677 /* Activity is occurring, so reset the polling backoff value to
678 a minimum for performance. */
679 timeout = MIN_TIMEOUT;
681 tty_flip_buffer_push(tty);
683 if (tty)
684 tty_kref_put(tty);
686 return poll_mask;
688 EXPORT_SYMBOL_GPL(hvc_poll);
691 * __hvc_resize() - Update terminal window size information.
692 * @hp: HVC console pointer
693 * @ws: Terminal window size structure
695 * Stores the specified window size information in the hvc structure of @hp.
696 * The function schedule the tty resize update.
698 * Locking: Locking free; the function MUST be called holding hp->lock
700 void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
702 hp->ws = ws;
703 schedule_work(&hp->tty_resize);
705 EXPORT_SYMBOL_GPL(__hvc_resize);
708 * This kthread is either polling or interrupt driven. This is determined by
709 * calling hvc_poll() who determines whether a console adapter support
710 * interrupts.
712 static int khvcd(void *unused)
714 int poll_mask;
715 struct hvc_struct *hp;
717 set_freezable();
718 do {
719 poll_mask = 0;
720 hvc_kicked = 0;
721 try_to_freeze();
722 wmb();
723 if (!cpus_are_in_xmon()) {
724 spin_lock(&hvc_structs_lock);
725 list_for_each_entry(hp, &hvc_structs, next) {
726 poll_mask |= hvc_poll(hp);
728 spin_unlock(&hvc_structs_lock);
729 } else
730 poll_mask |= HVC_POLL_READ;
731 if (hvc_kicked)
732 continue;
733 set_current_state(TASK_INTERRUPTIBLE);
734 if (!hvc_kicked) {
735 if (poll_mask == 0)
736 schedule();
737 else {
738 if (timeout < MAX_TIMEOUT)
739 timeout += (timeout >> 6) + 1;
741 msleep_interruptible(timeout);
744 __set_current_state(TASK_RUNNING);
745 } while (!kthread_should_stop());
747 return 0;
750 static int hvc_tiocmget(struct tty_struct *tty)
752 struct hvc_struct *hp = tty->driver_data;
754 if (!hp || !hp->ops->tiocmget)
755 return -EINVAL;
756 return hp->ops->tiocmget(hp);
759 static int hvc_tiocmset(struct tty_struct *tty,
760 unsigned int set, unsigned int clear)
762 struct hvc_struct *hp = tty->driver_data;
764 if (!hp || !hp->ops->tiocmset)
765 return -EINVAL;
766 return hp->ops->tiocmset(hp, set, clear);
769 static const struct tty_operations hvc_ops = {
770 .open = hvc_open,
771 .close = hvc_close,
772 .write = hvc_write,
773 .hangup = hvc_hangup,
774 .unthrottle = hvc_unthrottle,
775 .write_room = hvc_write_room,
776 .chars_in_buffer = hvc_chars_in_buffer,
777 .tiocmget = hvc_tiocmget,
778 .tiocmset = hvc_tiocmset,
781 struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
782 const struct hv_ops *ops,
783 int outbuf_size)
785 struct hvc_struct *hp;
786 int i;
788 /* We wait until a driver actually comes along */
789 if (!hvc_driver) {
790 int err = hvc_init();
791 if (err)
792 return ERR_PTR(err);
795 hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
796 GFP_KERNEL);
797 if (!hp)
798 return ERR_PTR(-ENOMEM);
800 hp->vtermno = vtermno;
801 hp->data = data;
802 hp->ops = ops;
803 hp->outbuf_size = outbuf_size;
804 hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
806 kref_init(&hp->kref);
808 INIT_WORK(&hp->tty_resize, hvc_set_winsz);
809 spin_lock_init(&hp->lock);
810 spin_lock(&hvc_structs_lock);
813 * find index to use:
814 * see if this vterm id matches one registered for console.
816 for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
817 if (vtermnos[i] == hp->vtermno &&
818 cons_ops[i] == hp->ops)
819 break;
821 /* no matching slot, just use a counter */
822 if (i >= MAX_NR_HVC_CONSOLES)
823 i = ++last_hvc;
825 hp->index = i;
827 list_add_tail(&(hp->next), &hvc_structs);
828 spin_unlock(&hvc_structs_lock);
830 return hp;
832 EXPORT_SYMBOL_GPL(hvc_alloc);
834 int hvc_remove(struct hvc_struct *hp)
836 unsigned long flags;
837 struct tty_struct *tty;
839 spin_lock_irqsave(&hp->lock, flags);
840 tty = tty_kref_get(hp->tty);
842 if (hp->index < MAX_NR_HVC_CONSOLES)
843 vtermnos[hp->index] = -1;
845 /* Don't whack hp->irq because tty_hangup() will need to free the irq. */
847 spin_unlock_irqrestore(&hp->lock, flags);
850 * We 'put' the instance that was grabbed when the kref instance
851 * was initialized using kref_init(). Let the last holder of this
852 * kref cause it to be removed, which will probably be the tty_vhangup
853 * below.
855 kref_put(&hp->kref, destroy_hvc_struct);
858 * This function call will auto chain call hvc_hangup.
860 if (tty) {
861 tty_vhangup(tty);
862 tty_kref_put(tty);
864 return 0;
866 EXPORT_SYMBOL_GPL(hvc_remove);
868 /* Driver initialization: called as soon as someone uses hvc_alloc(). */
869 static int hvc_init(void)
871 struct tty_driver *drv;
872 int err;
874 /* We need more than hvc_count adapters due to hotplug additions. */
875 drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
876 if (!drv) {
877 err = -ENOMEM;
878 goto out;
881 drv->owner = THIS_MODULE;
882 drv->driver_name = "hvc";
883 drv->name = "hvc";
884 drv->major = HVC_MAJOR;
885 drv->minor_start = HVC_MINOR;
886 drv->type = TTY_DRIVER_TYPE_SYSTEM;
887 drv->init_termios = tty_std_termios;
888 drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_RESET_TERMIOS;
889 tty_set_operations(drv, &hvc_ops);
891 /* Always start the kthread because there can be hotplug vty adapters
892 * added later. */
893 hvc_task = kthread_run(khvcd, NULL, "khvcd");
894 if (IS_ERR(hvc_task)) {
895 printk(KERN_ERR "Couldn't create kthread for console.\n");
896 err = PTR_ERR(hvc_task);
897 goto put_tty;
900 err = tty_register_driver(drv);
901 if (err) {
902 printk(KERN_ERR "Couldn't register hvc console driver\n");
903 goto stop_thread;
907 * Make sure tty is fully registered before allowing it to be
908 * found by hvc_console_device.
910 smp_mb();
911 hvc_driver = drv;
912 return 0;
914 stop_thread:
915 kthread_stop(hvc_task);
916 hvc_task = NULL;
917 put_tty:
918 put_tty_driver(drv);
919 out:
920 return err;
923 /* This isn't particularly necessary due to this being a console driver
924 * but it is nice to be thorough.
926 static void __exit hvc_exit(void)
928 if (hvc_driver) {
929 kthread_stop(hvc_task);
931 tty_unregister_driver(hvc_driver);
932 /* return tty_struct instances allocated in hvc_init(). */
933 put_tty_driver(hvc_driver);
934 unregister_console(&hvc_console);
937 module_exit(hvc_exit);