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/major.h>
33 #include <linux/atomic.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>
42 #include <linux/serial_core.h>
44 #include <linux/uaccess.h>
46 #include "hvc_console.h"
52 * Wait this long per iteration while trying to push buffered data to the
53 * hypervisor before allowing the tty to complete a close operation.
55 #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
58 * These sizes are most efficient for vio, because they are the
59 * native transfer size. We could make them selectable in the
60 * future to better deal with backends that want other buffer sizes.
65 #define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
67 static struct tty_driver *hvc_driver;
68 static struct task_struct *hvc_task;
70 /* Picks up late kicks after list walk but before schedule() */
71 static int hvc_kicked;
73 /* hvc_init is triggered from hvc_alloc, i.e. only when actually used */
74 static atomic_t hvc_needs_init __read_mostly = ATOMIC_INIT(-1);
76 static int hvc_init(void);
78 #ifdef CONFIG_MAGIC_SYSRQ
79 static int sysrq_pressed;
82 /* dynamic list of hvc_struct instances */
83 static LIST_HEAD(hvc_structs);
86 * Protect the list of hvc_struct instances from inserts and removals during
89 static DEFINE_SPINLOCK(hvc_structs_lock);
92 * This value is used to assign a tty->index value to a hvc_struct based
93 * upon order of exposure via hvc_probe(), when we can not match it to
94 * a console candidate registered with hvc_instantiate().
96 static int last_hvc = -1;
99 * Do not call this function with either the hvc_structs_lock or the hvc_struct
100 * lock held. If successful, this function increments the kref reference
101 * count against the target hvc_struct so it should be released when finished.
103 static struct hvc_struct *hvc_get_by_index(int index)
105 struct hvc_struct *hp;
108 spin_lock(&hvc_structs_lock);
110 list_for_each_entry(hp, &hvc_structs, next) {
111 spin_lock_irqsave(&hp->lock, flags);
112 if (hp->index == index) {
113 tty_port_get(&hp->port);
114 spin_unlock_irqrestore(&hp->lock, flags);
115 spin_unlock(&hvc_structs_lock);
118 spin_unlock_irqrestore(&hp->lock, flags);
122 spin_unlock(&hvc_structs_lock);
128 * Initial console vtermnos for console API usage prior to full console
129 * initialization. Any vty adapter outside this range will not have usable
130 * console interfaces but can still be used as a tty device. This has to be
131 * static because kmalloc will not work during early console init.
133 static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
134 static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
135 {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
138 * Console APIs, NOT TTY. These APIs are available immediately when
139 * hvc_console_setup() finds adapters.
142 static void hvc_console_print(struct console *co, const char *b,
145 char c[N_OUTBUF] __ALIGNED__;
146 unsigned i = 0, n = 0;
147 int r, donecr = 0, index = co->index;
149 /* Console access attempt outside of acceptable console range. */
150 if (index >= MAX_NR_HVC_CONSOLES)
153 /* This console adapter was removed so it is not usable. */
154 if (vtermnos[index] == -1)
157 while (count > 0 || i > 0) {
158 if (count > 0 && i < sizeof(c)) {
159 if (b[n] == '\n' && !donecr) {
168 r = cons_ops[index]->put_chars(vtermnos[index], c, i);
170 /* throw away characters on error
171 * but spin in case of -EAGAIN */
183 static struct tty_driver *hvc_console_device(struct console *c, int *index)
185 if (vtermnos[c->index] == -1)
192 static int hvc_console_setup(struct console *co, char *options)
194 if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
197 if (vtermnos[co->index] == -1)
203 static struct console hvc_console = {
205 .write = hvc_console_print,
206 .device = hvc_console_device,
207 .setup = hvc_console_setup,
208 .flags = CON_PRINTBUFFER,
213 * Early console initialization. Precedes driver initialization.
215 * (1) we are first, and the user specified another driver
216 * -- index will remain -1
217 * (2) we are first and the user specified no driver
218 * -- index will be set to 0, then we will fail setup.
219 * (3) we are first and the user specified our driver
220 * -- index will be set to user specified driver, and we will fail
221 * (4) we are after driver, and this initcall will register us
222 * -- if the user didn't specify a driver then the console will match
224 * Note that for cases 2 and 3, we will match later when the io driver
225 * calls hvc_instantiate() and call register again.
227 static int __init hvc_console_init(void)
229 register_console(&hvc_console);
232 console_initcall(hvc_console_init);
234 /* callback when the kboject ref count reaches zero. */
235 static void hvc_port_destruct(struct tty_port *port)
237 struct hvc_struct *hp = container_of(port, struct hvc_struct, port);
240 spin_lock(&hvc_structs_lock);
242 spin_lock_irqsave(&hp->lock, flags);
243 list_del(&(hp->next));
244 spin_unlock_irqrestore(&hp->lock, flags);
246 spin_unlock(&hvc_structs_lock);
251 static void hvc_check_console(int index)
253 /* Already enabled, bail out */
254 if (hvc_console.flags & CON_ENABLED)
257 /* If this index is what the user requested, then register
258 * now (setup won't fail at this point). It's ok to just
259 * call register again if previously .setup failed.
261 if (index == hvc_console.index)
262 register_console(&hvc_console);
266 * hvc_instantiate() is an early console discovery method which locates
267 * consoles * prior to the vio subsystem discovering them. Hotplugged
268 * vty adapters do NOT get an hvc_instantiate() callback since they
269 * appear after early console init.
271 int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
273 struct hvc_struct *hp;
275 if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
278 if (vtermnos[index] != -1)
281 /* make sure no no tty has been registered in this index */
282 hp = hvc_get_by_index(index);
284 tty_port_put(&hp->port);
288 vtermnos[index] = vtermno;
289 cons_ops[index] = ops;
291 /* check if we need to re-register the kernel console */
292 hvc_check_console(index);
296 EXPORT_SYMBOL_GPL(hvc_instantiate);
298 /* Wake the sleeping khvcd */
302 wake_up_process(hvc_task);
304 EXPORT_SYMBOL_GPL(hvc_kick);
306 static void hvc_unthrottle(struct tty_struct *tty)
311 static int hvc_install(struct tty_driver *driver, struct tty_struct *tty)
313 struct hvc_struct *hp;
316 /* Auto increments kref reference if found. */
317 hp = hvc_get_by_index(tty->index);
321 tty->driver_data = hp;
323 rc = tty_port_install(&hp->port, driver, tty);
325 tty_port_put(&hp->port);
330 * The TTY interface won't be used until after the vio layer has exposed the vty
331 * adapter to the kernel.
333 static int hvc_open(struct tty_struct *tty, struct file * filp)
335 struct hvc_struct *hp = tty->driver_data;
339 spin_lock_irqsave(&hp->port.lock, flags);
340 /* Check and then increment for fast path open. */
341 if (hp->port.count++ > 0) {
342 spin_unlock_irqrestore(&hp->port.lock, flags);
345 } /* else count == 0 */
346 spin_unlock_irqrestore(&hp->port.lock, flags);
348 tty_port_tty_set(&hp->port, tty);
350 if (hp->ops->notifier_add)
351 rc = hp->ops->notifier_add(hp, hp->data);
354 * If the notifier fails we return an error. The tty layer
355 * will call hvc_close() after a failed open but we don't want to clean
356 * up there so we'll clean up here and clear out the previously set
357 * tty fields and return the kref reference.
360 printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
362 /* We are ready... raise DTR/RTS */
364 if (hp->ops->dtr_rts)
365 hp->ops->dtr_rts(hp, 1);
366 tty_port_set_initialized(&hp->port, true);
369 /* Force wakeup of the polling thread */
375 static void hvc_close(struct tty_struct *tty, struct file * filp)
377 struct hvc_struct *hp = tty->driver_data;
380 if (tty_hung_up_p(filp))
383 spin_lock_irqsave(&hp->port.lock, flags);
385 if (--hp->port.count == 0) {
386 spin_unlock_irqrestore(&hp->port.lock, flags);
387 /* We are done with the tty pointer now. */
388 tty_port_tty_set(&hp->port, NULL);
390 if (!tty_port_initialized(&hp->port))
394 if (hp->ops->dtr_rts)
395 hp->ops->dtr_rts(hp, 0);
397 if (hp->ops->notifier_del)
398 hp->ops->notifier_del(hp, hp->data);
400 /* cancel pending tty resize work */
401 cancel_work_sync(&hp->tty_resize);
404 * Chain calls chars_in_buffer() and returns immediately if
405 * there is no buffered data otherwise sleeps on a wait queue
406 * waking periodically to check chars_in_buffer().
408 tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
409 tty_port_set_initialized(&hp->port, false);
411 if (hp->port.count < 0)
412 printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
413 hp->vtermno, hp->port.count);
414 spin_unlock_irqrestore(&hp->port.lock, flags);
418 static void hvc_cleanup(struct tty_struct *tty)
420 struct hvc_struct *hp = tty->driver_data;
422 tty_port_put(&hp->port);
425 static void hvc_hangup(struct tty_struct *tty)
427 struct hvc_struct *hp = tty->driver_data;
433 /* cancel pending tty resize work */
434 cancel_work_sync(&hp->tty_resize);
436 spin_lock_irqsave(&hp->port.lock, flags);
439 * The N_TTY line discipline has problems such that in a close vs
440 * open->hangup case this can be called after the final close so prevent
441 * that from happening for now.
443 if (hp->port.count <= 0) {
444 spin_unlock_irqrestore(&hp->port.lock, flags);
449 spin_unlock_irqrestore(&hp->port.lock, flags);
450 tty_port_tty_set(&hp->port, NULL);
454 if (hp->ops->notifier_hangup)
455 hp->ops->notifier_hangup(hp, hp->data);
459 * Push buffered characters whether they were just recently buffered or waiting
460 * on a blocked hypervisor. Call this function with hp->lock held.
462 static int hvc_push(struct hvc_struct *hp)
466 n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
468 if (n == 0 || n == -EAGAIN) {
472 /* throw away output on error; this happens when
473 there is no session connected to the vterm. */
477 if (hp->n_outbuf > 0)
478 memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
485 static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
487 struct hvc_struct *hp = tty->driver_data;
489 int rsize, written = 0;
491 /* This write was probably executed during a tty close. */
495 /* FIXME what's this (unprotected) check for? */
496 if (hp->port.count <= 0)
499 spin_lock_irqsave(&hp->lock, flags);
501 /* Push pending writes */
502 if (hp->n_outbuf > 0)
505 while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
508 memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
511 hp->n_outbuf += rsize;
515 spin_unlock_irqrestore(&hp->lock, flags);
518 * Racy, but harmless, kick thread if there is still pending data.
527 * hvc_set_winsz() - Resize the hvc tty terminal window.
528 * @work: work structure.
530 * The routine shall not be called within an atomic context because it
535 static void hvc_set_winsz(struct work_struct *work)
537 struct hvc_struct *hp;
538 unsigned long hvc_flags;
539 struct tty_struct *tty;
542 hp = container_of(work, struct hvc_struct, tty_resize);
544 tty = tty_port_tty_get(&hp->port);
548 spin_lock_irqsave(&hp->lock, hvc_flags);
550 spin_unlock_irqrestore(&hp->lock, hvc_flags);
552 tty_do_resize(tty, &ws);
557 * This is actually a contract between the driver and the tty layer outlining
558 * how much write room the driver can guarantee will be sent OR BUFFERED. This
559 * driver MUST honor the return value.
561 static int hvc_write_room(struct tty_struct *tty)
563 struct hvc_struct *hp = tty->driver_data;
568 return hp->outbuf_size - hp->n_outbuf;
571 static int hvc_chars_in_buffer(struct tty_struct *tty)
573 struct hvc_struct *hp = tty->driver_data;
581 * timeout will vary between the MIN and MAX values defined here. By default
582 * and during console activity we will use a default MIN_TIMEOUT of 10. When
583 * the console is idle, we increase the timeout value on each pass through
584 * msleep until we reach the max. This may be noticeable as a brief (average
585 * one second) delay on the console before the console responds to input when
586 * there has been no input for some time.
588 #define MIN_TIMEOUT (10)
589 #define MAX_TIMEOUT (2000)
590 static u32 timeout = MIN_TIMEOUT;
592 #define HVC_POLL_READ 0x00000001
593 #define HVC_POLL_WRITE 0x00000002
595 int hvc_poll(struct hvc_struct *hp)
597 struct tty_struct *tty;
598 int i, n, poll_mask = 0;
599 char buf[N_INBUF] __ALIGNED__;
602 int written_total = 0;
604 spin_lock_irqsave(&hp->lock, flags);
606 /* Push pending writes */
607 if (hp->n_outbuf > 0)
608 written_total = hvc_push(hp);
610 /* Reschedule us if still some write pending */
611 if (hp->n_outbuf > 0) {
612 poll_mask |= HVC_POLL_WRITE;
613 /* If hvc_push() was not able to write, sleep a few msecs */
614 timeout = (written_total) ? 0 : MIN_TIMEOUT;
617 /* No tty attached, just skip */
618 tty = tty_port_tty_get(&hp->port);
622 /* Now check if we can get data (are we throttled ?) */
623 if (tty_throttled(tty))
626 /* If we aren't notifier driven and aren't throttled, we always
627 * request a reschedule
629 if (!hp->irq_requested)
630 poll_mask |= HVC_POLL_READ;
632 /* Read data if any */
634 int count = tty_buffer_request_room(&hp->port, N_INBUF);
636 /* If flip is full, just reschedule a later read */
638 poll_mask |= HVC_POLL_READ;
642 n = hp->ops->get_chars(hp->vtermno, buf, count);
644 /* Hangup the tty when disconnected from host */
646 spin_unlock_irqrestore(&hp->lock, flags);
648 spin_lock_irqsave(&hp->lock, flags);
649 } else if ( n == -EAGAIN ) {
651 * Some back-ends can only ensure a certain min
652 * num of bytes read, which may be > 'count'.
653 * Let the tty clear the flip buff to make room.
655 poll_mask |= HVC_POLL_READ;
659 for (i = 0; i < n; ++i) {
660 #ifdef CONFIG_MAGIC_SYSRQ
661 if (hp->index == hvc_console.index) {
662 /* Handle the SysRq Hack */
663 /* XXX should support a sequence */
664 if (buf[i] == '\x0f') { /* ^O */
665 /* if ^O is pressed again, reset
666 * sysrq_pressed and flip ^O char */
667 sysrq_pressed = !sysrq_pressed;
670 } else if (sysrq_pressed) {
671 handle_sysrq(buf[i]);
676 #endif /* CONFIG_MAGIC_SYSRQ */
677 tty_insert_flip_char(&hp->port, buf[i], 0);
683 /* Wakeup write queue if necessary */
689 spin_unlock_irqrestore(&hp->lock, flags);
692 /* Activity is occurring, so reset the polling backoff value to
693 a minimum for performance. */
694 timeout = MIN_TIMEOUT;
696 tty_flip_buffer_push(&hp->port);
702 EXPORT_SYMBOL_GPL(hvc_poll);
705 * __hvc_resize() - Update terminal window size information.
706 * @hp: HVC console pointer
707 * @ws: Terminal window size structure
709 * Stores the specified window size information in the hvc structure of @hp.
710 * The function schedule the tty resize update.
712 * Locking: Locking free; the function MUST be called holding hp->lock
714 void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
717 schedule_work(&hp->tty_resize);
719 EXPORT_SYMBOL_GPL(__hvc_resize);
722 * This kthread is either polling or interrupt driven. This is determined by
723 * calling hvc_poll() who determines whether a console adapter support
726 static int khvcd(void *unused)
729 struct hvc_struct *hp;
737 if (!cpus_are_in_xmon()) {
738 spin_lock(&hvc_structs_lock);
739 list_for_each_entry(hp, &hvc_structs, next) {
740 poll_mask |= hvc_poll(hp);
742 spin_unlock(&hvc_structs_lock);
744 poll_mask |= HVC_POLL_READ;
747 set_current_state(TASK_INTERRUPTIBLE);
752 unsigned long j_timeout;
754 if (timeout < MAX_TIMEOUT)
755 timeout += (timeout >> 6) + 1;
758 * We don't use msleep_interruptible otherwise
759 * "kick" will fail to wake us up
761 j_timeout = msecs_to_jiffies(timeout) + 1;
762 schedule_timeout_interruptible(j_timeout);
765 __set_current_state(TASK_RUNNING);
766 } while (!kthread_should_stop());
771 static int hvc_tiocmget(struct tty_struct *tty)
773 struct hvc_struct *hp = tty->driver_data;
775 if (!hp || !hp->ops->tiocmget)
777 return hp->ops->tiocmget(hp);
780 static int hvc_tiocmset(struct tty_struct *tty,
781 unsigned int set, unsigned int clear)
783 struct hvc_struct *hp = tty->driver_data;
785 if (!hp || !hp->ops->tiocmset)
787 return hp->ops->tiocmset(hp, set, clear);
790 #ifdef CONFIG_CONSOLE_POLL
791 static int hvc_poll_init(struct tty_driver *driver, int line, char *options)
796 static int hvc_poll_get_char(struct tty_driver *driver, int line)
798 struct tty_struct *tty = driver->ttys[0];
799 struct hvc_struct *hp = tty->driver_data;
803 n = hp->ops->get_chars(hp->vtermno, &ch, 1);
811 static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch)
813 struct tty_struct *tty = driver->ttys[0];
814 struct hvc_struct *hp = tty->driver_data;
818 n = hp->ops->put_chars(hp->vtermno, &ch, 1);
823 static const struct tty_operations hvc_ops = {
824 .install = hvc_install,
827 .cleanup = hvc_cleanup,
829 .hangup = hvc_hangup,
830 .unthrottle = hvc_unthrottle,
831 .write_room = hvc_write_room,
832 .chars_in_buffer = hvc_chars_in_buffer,
833 .tiocmget = hvc_tiocmget,
834 .tiocmset = hvc_tiocmset,
835 #ifdef CONFIG_CONSOLE_POLL
836 .poll_init = hvc_poll_init,
837 .poll_get_char = hvc_poll_get_char,
838 .poll_put_char = hvc_poll_put_char,
842 static const struct tty_port_operations hvc_port_ops = {
843 .destruct = hvc_port_destruct,
846 struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
847 const struct hv_ops *ops,
850 struct hvc_struct *hp;
853 /* We wait until a driver actually comes along */
854 if (atomic_inc_not_zero(&hvc_needs_init)) {
855 int err = hvc_init();
860 hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
863 return ERR_PTR(-ENOMEM);
865 hp->vtermno = vtermno;
868 hp->outbuf_size = outbuf_size;
869 hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
871 tty_port_init(&hp->port);
872 hp->port.ops = &hvc_port_ops;
874 INIT_WORK(&hp->tty_resize, hvc_set_winsz);
875 spin_lock_init(&hp->lock);
876 spin_lock(&hvc_structs_lock);
880 * see if this vterm id matches one registered for console.
882 for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
883 if (vtermnos[i] == hp->vtermno &&
884 cons_ops[i] == hp->ops)
887 if (i >= MAX_NR_HVC_CONSOLES) {
889 /* find 'empty' slot for console */
890 for (i = 0; i < MAX_NR_HVC_CONSOLES && vtermnos[i] != -1; i++) {
893 /* no matching slot, just use a counter */
894 if (i == MAX_NR_HVC_CONSOLES)
895 i = ++last_hvc + MAX_NR_HVC_CONSOLES;
899 if (i < MAX_NR_HVC_CONSOLES) {
901 vtermnos[i] = vtermno;
904 list_add_tail(&(hp->next), &hvc_structs);
905 spin_unlock(&hvc_structs_lock);
907 /* check if we need to re-register the kernel console */
908 hvc_check_console(i);
912 EXPORT_SYMBOL_GPL(hvc_alloc);
914 int hvc_remove(struct hvc_struct *hp)
917 struct tty_struct *tty;
919 tty = tty_port_tty_get(&hp->port);
922 spin_lock_irqsave(&hp->lock, flags);
923 if (hp->index < MAX_NR_HVC_CONSOLES) {
924 vtermnos[hp->index] = -1;
925 cons_ops[hp->index] = NULL;
928 /* Don't whack hp->irq because tty_hangup() will need to free the irq. */
930 spin_unlock_irqrestore(&hp->lock, flags);
934 * We 'put' the instance that was grabbed when the kref instance
935 * was initialized using kref_init(). Let the last holder of this
936 * kref cause it to be removed, which will probably be the tty_vhangup
939 tty_port_put(&hp->port);
942 * This function call will auto chain call hvc_hangup.
950 EXPORT_SYMBOL_GPL(hvc_remove);
952 /* Driver initialization: called as soon as someone uses hvc_alloc(). */
953 static int hvc_init(void)
955 struct tty_driver *drv;
958 /* We need more than hvc_count adapters due to hotplug additions. */
959 drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
965 drv->driver_name = "hvc";
967 drv->major = HVC_MAJOR;
968 drv->minor_start = HVC_MINOR;
969 drv->type = TTY_DRIVER_TYPE_SYSTEM;
970 drv->init_termios = tty_std_termios;
971 drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_RESET_TERMIOS;
972 tty_set_operations(drv, &hvc_ops);
974 /* Always start the kthread because there can be hotplug vty adapters
976 hvc_task = kthread_run(khvcd, NULL, "khvcd");
977 if (IS_ERR(hvc_task)) {
978 printk(KERN_ERR "Couldn't create kthread for console.\n");
979 err = PTR_ERR(hvc_task);
983 err = tty_register_driver(drv);
985 printk(KERN_ERR "Couldn't register hvc console driver\n");
990 * Make sure tty is fully registered before allowing it to be
991 * found by hvc_console_device.
998 kthread_stop(hvc_task);
1001 put_tty_driver(drv);