1 // SPDX-License-Identifier: GPL-2.0+
3 * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
4 * Copyright (C) 2001 Paul Mackerras <paulus@au.ibm.com>, IBM
5 * Copyright (C) 2004 Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp.
6 * Copyright (C) 2004 IBM Corporation
8 * Additional Author(s):
9 * Ryan S. Arnold <rsa@us.ibm.com>
12 #include <linux/console.h>
13 #include <linux/cpumask.h>
14 #include <linux/init.h>
15 #include <linux/kbd_kern.h>
16 #include <linux/kernel.h>
17 #include <linux/kthread.h>
18 #include <linux/list.h>
19 #include <linux/major.h>
20 #include <linux/atomic.h>
21 #include <linux/sysrq.h>
22 #include <linux/tty.h>
23 #include <linux/tty_flip.h>
24 #include <linux/sched.h>
25 #include <linux/spinlock.h>
26 #include <linux/delay.h>
27 #include <linux/freezer.h>
28 #include <linux/slab.h>
29 #include <linux/serial_core.h>
31 #include <linux/uaccess.h>
33 #include "hvc_console.h"
39 * Wait this long per iteration while trying to push buffered data to the
40 * hypervisor before allowing the tty to complete a close operation.
42 #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
45 * These sizes are most efficient for vio, because they are the
46 * native transfer size. We could make them selectable in the
47 * future to better deal with backends that want other buffer sizes.
52 #define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
54 static struct tty_driver *hvc_driver;
55 static struct task_struct *hvc_task;
57 /* Picks up late kicks after list walk but before schedule() */
58 static int hvc_kicked;
60 /* hvc_init is triggered from hvc_alloc, i.e. only when actually used */
61 static atomic_t hvc_needs_init __read_mostly = ATOMIC_INIT(-1);
63 static int hvc_init(void);
65 #ifdef CONFIG_MAGIC_SYSRQ
66 static int sysrq_pressed;
69 /* dynamic list of hvc_struct instances */
70 static LIST_HEAD(hvc_structs);
73 * Protect the list of hvc_struct instances from inserts and removals during
76 static DEFINE_MUTEX(hvc_structs_mutex);
79 * This value is used to assign a tty->index value to a hvc_struct based
80 * upon order of exposure via hvc_probe(), when we can not match it to
81 * a console candidate registered with hvc_instantiate().
83 static int last_hvc = -1;
86 * Do not call this function with either the hvc_structs_mutex or the hvc_struct
87 * lock held. If successful, this function increments the kref reference
88 * count against the target hvc_struct so it should be released when finished.
90 static struct hvc_struct *hvc_get_by_index(int index)
92 struct hvc_struct *hp;
95 mutex_lock(&hvc_structs_mutex);
97 list_for_each_entry(hp, &hvc_structs, next) {
98 spin_lock_irqsave(&hp->lock, flags);
99 if (hp->index == index) {
100 tty_port_get(&hp->port);
101 spin_unlock_irqrestore(&hp->lock, flags);
102 mutex_unlock(&hvc_structs_mutex);
105 spin_unlock_irqrestore(&hp->lock, flags);
108 mutex_unlock(&hvc_structs_mutex);
113 static int __hvc_flush(const struct hv_ops *ops, uint32_t vtermno, bool wait)
119 return ops->flush(vtermno, wait);
123 static int hvc_console_flush(const struct hv_ops *ops, uint32_t vtermno)
125 return __hvc_flush(ops, vtermno, false);
129 * Wait for the console to flush before writing more to it. This sleeps.
131 static int hvc_flush(struct hvc_struct *hp)
133 return __hvc_flush(hp->ops, hp->vtermno, true);
137 * Initial console vtermnos for console API usage prior to full console
138 * initialization. Any vty adapter outside this range will not have usable
139 * console interfaces but can still be used as a tty device. This has to be
140 * static because kmalloc will not work during early console init.
142 static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
143 static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
144 {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
147 * Console APIs, NOT TTY. These APIs are available immediately when
148 * hvc_console_setup() finds adapters.
151 static void hvc_console_print(struct console *co, const char *b,
154 char c[N_OUTBUF] __ALIGNED__;
155 unsigned i = 0, n = 0;
156 int r, donecr = 0, index = co->index;
158 /* Console access attempt outside of acceptable console range. */
159 if (index >= MAX_NR_HVC_CONSOLES)
162 /* This console adapter was removed so it is not usable. */
163 if (vtermnos[index] == -1)
166 while (count > 0 || i > 0) {
167 if (count > 0 && i < sizeof(c)) {
168 if (b[n] == '\n' && !donecr) {
177 r = cons_ops[index]->put_chars(vtermnos[index], c, i);
179 /* throw away characters on error
180 * but spin in case of -EAGAIN */
184 hvc_console_flush(cons_ops[index],
194 hvc_console_flush(cons_ops[index], vtermnos[index]);
197 static struct tty_driver *hvc_console_device(struct console *c, int *index)
199 if (vtermnos[c->index] == -1)
206 static int hvc_console_setup(struct console *co, char *options)
208 if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
211 if (vtermnos[co->index] == -1)
217 static struct console hvc_console = {
219 .write = hvc_console_print,
220 .device = hvc_console_device,
221 .setup = hvc_console_setup,
222 .flags = CON_PRINTBUFFER,
227 * Early console initialization. Precedes driver initialization.
229 * (1) we are first, and the user specified another driver
230 * -- index will remain -1
231 * (2) we are first and the user specified no driver
232 * -- index will be set to 0, then we will fail setup.
233 * (3) we are first and the user specified our driver
234 * -- index will be set to user specified driver, and we will fail
235 * (4) we are after driver, and this initcall will register us
236 * -- if the user didn't specify a driver then the console will match
238 * Note that for cases 2 and 3, we will match later when the io driver
239 * calls hvc_instantiate() and call register again.
241 static int __init hvc_console_init(void)
243 register_console(&hvc_console);
246 console_initcall(hvc_console_init);
248 /* callback when the kboject ref count reaches zero. */
249 static void hvc_port_destruct(struct tty_port *port)
251 struct hvc_struct *hp = container_of(port, struct hvc_struct, port);
254 mutex_lock(&hvc_structs_mutex);
256 spin_lock_irqsave(&hp->lock, flags);
257 list_del(&(hp->next));
258 spin_unlock_irqrestore(&hp->lock, flags);
260 mutex_unlock(&hvc_structs_mutex);
265 static void hvc_check_console(int index)
267 /* Already enabled, bail out */
268 if (hvc_console.flags & CON_ENABLED)
271 /* If this index is what the user requested, then register
272 * now (setup won't fail at this point). It's ok to just
273 * call register again if previously .setup failed.
275 if (index == hvc_console.index)
276 register_console(&hvc_console);
280 * hvc_instantiate() is an early console discovery method which locates
281 * consoles * prior to the vio subsystem discovering them. Hotplugged
282 * vty adapters do NOT get an hvc_instantiate() callback since they
283 * appear after early console init.
285 int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
287 struct hvc_struct *hp;
289 if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
292 if (vtermnos[index] != -1)
295 /* make sure no no tty has been registered in this index */
296 hp = hvc_get_by_index(index);
298 tty_port_put(&hp->port);
302 vtermnos[index] = vtermno;
303 cons_ops[index] = ops;
305 /* reserve all indices up to and including this index */
306 if (last_hvc < index)
309 /* check if we need to re-register the kernel console */
310 hvc_check_console(index);
314 EXPORT_SYMBOL_GPL(hvc_instantiate);
316 /* Wake the sleeping khvcd */
320 wake_up_process(hvc_task);
322 EXPORT_SYMBOL_GPL(hvc_kick);
324 static void hvc_unthrottle(struct tty_struct *tty)
329 static int hvc_install(struct tty_driver *driver, struct tty_struct *tty)
331 struct hvc_struct *hp;
334 /* Auto increments kref reference if found. */
335 hp = hvc_get_by_index(tty->index);
339 tty->driver_data = hp;
341 rc = tty_port_install(&hp->port, driver, tty);
343 tty_port_put(&hp->port);
348 * The TTY interface won't be used until after the vio layer has exposed the vty
349 * adapter to the kernel.
351 static int hvc_open(struct tty_struct *tty, struct file * filp)
353 struct hvc_struct *hp = tty->driver_data;
357 spin_lock_irqsave(&hp->port.lock, flags);
358 /* Check and then increment for fast path open. */
359 if (hp->port.count++ > 0) {
360 spin_unlock_irqrestore(&hp->port.lock, flags);
363 } /* else count == 0 */
364 spin_unlock_irqrestore(&hp->port.lock, flags);
366 tty_port_tty_set(&hp->port, tty);
368 if (hp->ops->notifier_add)
369 rc = hp->ops->notifier_add(hp, hp->data);
372 * If the notifier fails we return an error. The tty layer
373 * will call hvc_close() after a failed open but we don't want to clean
374 * up there so we'll clean up here and clear out the previously set
375 * tty fields and return the kref reference.
378 tty_port_tty_set(&hp->port, NULL);
379 tty->driver_data = NULL;
380 tty_port_put(&hp->port);
381 printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
383 /* We are ready... raise DTR/RTS */
385 if (hp->ops->dtr_rts)
386 hp->ops->dtr_rts(hp, 1);
388 /* Force wakeup of the polling thread */
394 static void hvc_close(struct tty_struct *tty, struct file * filp)
396 struct hvc_struct *hp;
399 if (tty_hung_up_p(filp))
403 * No driver_data means that this close was issued after a failed
404 * hvc_open by the tty layer's release_dev() function and we can just
405 * exit cleanly because the kref reference wasn't made.
407 if (!tty->driver_data)
410 hp = tty->driver_data;
412 spin_lock_irqsave(&hp->port.lock, flags);
414 if (--hp->port.count == 0) {
415 spin_unlock_irqrestore(&hp->port.lock, flags);
416 /* We are done with the tty pointer now. */
417 tty_port_tty_set(&hp->port, NULL);
420 if (hp->ops->dtr_rts)
421 hp->ops->dtr_rts(hp, 0);
423 if (hp->ops->notifier_del)
424 hp->ops->notifier_del(hp, hp->data);
426 /* cancel pending tty resize work */
427 cancel_work_sync(&hp->tty_resize);
430 * Chain calls chars_in_buffer() and returns immediately if
431 * there is no buffered data otherwise sleeps on a wait queue
432 * waking periodically to check chars_in_buffer().
434 tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
436 if (hp->port.count < 0)
437 printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
438 hp->vtermno, hp->port.count);
439 spin_unlock_irqrestore(&hp->port.lock, flags);
443 static void hvc_cleanup(struct tty_struct *tty)
445 struct hvc_struct *hp = tty->driver_data;
447 tty_port_put(&hp->port);
450 static void hvc_hangup(struct tty_struct *tty)
452 struct hvc_struct *hp = tty->driver_data;
458 /* cancel pending tty resize work */
459 cancel_work_sync(&hp->tty_resize);
461 spin_lock_irqsave(&hp->port.lock, flags);
464 * The N_TTY line discipline has problems such that in a close vs
465 * open->hangup case this can be called after the final close so prevent
466 * that from happening for now.
468 if (hp->port.count <= 0) {
469 spin_unlock_irqrestore(&hp->port.lock, flags);
474 spin_unlock_irqrestore(&hp->port.lock, flags);
475 tty_port_tty_set(&hp->port, NULL);
479 if (hp->ops->notifier_hangup)
480 hp->ops->notifier_hangup(hp, hp->data);
484 * Push buffered characters whether they were just recently buffered or waiting
485 * on a blocked hypervisor. Call this function with hp->lock held.
487 static int hvc_push(struct hvc_struct *hp)
491 n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
493 if (n == 0 || n == -EAGAIN) {
497 /* throw away output on error; this happens when
498 there is no session connected to the vterm. */
502 if (hp->n_outbuf > 0)
503 memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
510 static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
512 struct hvc_struct *hp = tty->driver_data;
514 int rsize, written = 0;
516 /* This write was probably executed during a tty close. */
520 /* FIXME what's this (unprotected) check for? */
521 if (hp->port.count <= 0)
525 spin_lock_irqsave(&hp->lock, flags);
527 rsize = hp->outbuf_size - hp->n_outbuf;
532 memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
535 hp->n_outbuf += rsize;
539 if (hp->n_outbuf > 0)
542 spin_unlock_irqrestore(&hp->lock, flags);
545 if (hp->n_outbuf > 0)
552 * Racy, but harmless, kick thread if there is still pending data.
561 * hvc_set_winsz() - Resize the hvc tty terminal window.
562 * @work: work structure.
564 * The routine shall not be called within an atomic context because it
569 static void hvc_set_winsz(struct work_struct *work)
571 struct hvc_struct *hp;
572 unsigned long hvc_flags;
573 struct tty_struct *tty;
576 hp = container_of(work, struct hvc_struct, tty_resize);
578 tty = tty_port_tty_get(&hp->port);
582 spin_lock_irqsave(&hp->lock, hvc_flags);
584 spin_unlock_irqrestore(&hp->lock, hvc_flags);
586 tty_do_resize(tty, &ws);
591 * This is actually a contract between the driver and the tty layer outlining
592 * how much write room the driver can guarantee will be sent OR BUFFERED. This
593 * driver MUST honor the return value.
595 static int hvc_write_room(struct tty_struct *tty)
597 struct hvc_struct *hp = tty->driver_data;
602 return hp->outbuf_size - hp->n_outbuf;
605 static int hvc_chars_in_buffer(struct tty_struct *tty)
607 struct hvc_struct *hp = tty->driver_data;
615 * timeout will vary between the MIN and MAX values defined here. By default
616 * and during console activity we will use a default MIN_TIMEOUT of 10. When
617 * the console is idle, we increase the timeout value on each pass through
618 * msleep until we reach the max. This may be noticeable as a brief (average
619 * one second) delay on the console before the console responds to input when
620 * there has been no input for some time.
622 #define MIN_TIMEOUT (10)
623 #define MAX_TIMEOUT (2000)
624 static u32 timeout = MIN_TIMEOUT;
626 #define HVC_POLL_READ 0x00000001
627 #define HVC_POLL_WRITE 0x00000002
629 static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
631 struct tty_struct *tty;
632 int i, n, count, poll_mask = 0;
633 char buf[N_INBUF] __ALIGNED__;
636 int written_total = 0;
638 spin_lock_irqsave(&hp->lock, flags);
640 /* Push pending writes */
641 if (hp->n_outbuf > 0)
642 written_total = hvc_push(hp);
644 /* Reschedule us if still some write pending */
645 if (hp->n_outbuf > 0) {
646 poll_mask |= HVC_POLL_WRITE;
647 /* If hvc_push() was not able to write, sleep a few msecs */
648 timeout = (written_total) ? 0 : MIN_TIMEOUT;
652 spin_unlock_irqrestore(&hp->lock, flags);
654 spin_lock_irqsave(&hp->lock, flags);
657 /* No tty attached, just skip */
658 tty = tty_port_tty_get(&hp->port);
662 /* Now check if we can get data (are we throttled ?) */
663 if (tty_throttled(tty))
666 /* If we aren't notifier driven and aren't throttled, we always
667 * request a reschedule
669 if (!hp->irq_requested)
670 poll_mask |= HVC_POLL_READ;
672 /* Read data if any */
674 count = tty_buffer_request_room(&hp->port, N_INBUF);
676 /* If flip is full, just reschedule a later read */
678 poll_mask |= HVC_POLL_READ;
682 n = hp->ops->get_chars(hp->vtermno, buf, count);
684 /* Hangup the tty when disconnected from host */
686 spin_unlock_irqrestore(&hp->lock, flags);
688 spin_lock_irqsave(&hp->lock, flags);
689 } else if ( n == -EAGAIN ) {
691 * Some back-ends can only ensure a certain min
692 * num of bytes read, which may be > 'count'.
693 * Let the tty clear the flip buff to make room.
695 poll_mask |= HVC_POLL_READ;
700 for (i = 0; i < n; ++i) {
701 #ifdef CONFIG_MAGIC_SYSRQ
702 if (hp->index == hvc_console.index) {
703 /* Handle the SysRq Hack */
704 /* XXX should support a sequence */
705 if (buf[i] == '\x0f') { /* ^O */
706 /* if ^O is pressed again, reset
707 * sysrq_pressed and flip ^O char */
708 sysrq_pressed = !sysrq_pressed;
711 } else if (sysrq_pressed) {
712 handle_sysrq(buf[i]);
717 #endif /* CONFIG_MAGIC_SYSRQ */
718 tty_insert_flip_char(&hp->port, buf[i], 0);
721 poll_mask |= HVC_POLL_READ;
725 /* Wakeup write queue if necessary */
731 spin_unlock_irqrestore(&hp->lock, flags);
734 /* Activity is occurring, so reset the polling backoff value to
735 a minimum for performance. */
736 timeout = MIN_TIMEOUT;
738 tty_flip_buffer_push(&hp->port);
745 int hvc_poll(struct hvc_struct *hp)
747 return __hvc_poll(hp, false);
749 EXPORT_SYMBOL_GPL(hvc_poll);
752 * __hvc_resize() - Update terminal window size information.
753 * @hp: HVC console pointer
754 * @ws: Terminal window size structure
756 * Stores the specified window size information in the hvc structure of @hp.
757 * The function schedule the tty resize update.
759 * Locking: Locking free; the function MUST be called holding hp->lock
761 void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
764 schedule_work(&hp->tty_resize);
766 EXPORT_SYMBOL_GPL(__hvc_resize);
769 * This kthread is either polling or interrupt driven. This is determined by
770 * calling hvc_poll() who determines whether a console adapter support
773 static int khvcd(void *unused)
776 struct hvc_struct *hp;
784 if (!cpus_are_in_xmon()) {
785 mutex_lock(&hvc_structs_mutex);
786 list_for_each_entry(hp, &hvc_structs, next) {
787 poll_mask |= __hvc_poll(hp, true);
790 mutex_unlock(&hvc_structs_mutex);
792 poll_mask |= HVC_POLL_READ;
795 set_current_state(TASK_INTERRUPTIBLE);
800 unsigned long j_timeout;
802 if (timeout < MAX_TIMEOUT)
803 timeout += (timeout >> 6) + 1;
806 * We don't use msleep_interruptible otherwise
807 * "kick" will fail to wake us up
809 j_timeout = msecs_to_jiffies(timeout) + 1;
810 schedule_timeout_interruptible(j_timeout);
813 __set_current_state(TASK_RUNNING);
814 } while (!kthread_should_stop());
819 static int hvc_tiocmget(struct tty_struct *tty)
821 struct hvc_struct *hp = tty->driver_data;
823 if (!hp || !hp->ops->tiocmget)
825 return hp->ops->tiocmget(hp);
828 static int hvc_tiocmset(struct tty_struct *tty,
829 unsigned int set, unsigned int clear)
831 struct hvc_struct *hp = tty->driver_data;
833 if (!hp || !hp->ops->tiocmset)
835 return hp->ops->tiocmset(hp, set, clear);
838 #ifdef CONFIG_CONSOLE_POLL
839 static int hvc_poll_init(struct tty_driver *driver, int line, char *options)
844 static int hvc_poll_get_char(struct tty_driver *driver, int line)
846 struct tty_struct *tty = driver->ttys[0];
847 struct hvc_struct *hp = tty->driver_data;
851 n = hp->ops->get_chars(hp->vtermno, &ch, 1);
859 static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch)
861 struct tty_struct *tty = driver->ttys[0];
862 struct hvc_struct *hp = tty->driver_data;
866 n = hp->ops->put_chars(hp->vtermno, &ch, 1);
871 static const struct tty_operations hvc_ops = {
872 .install = hvc_install,
875 .cleanup = hvc_cleanup,
877 .hangup = hvc_hangup,
878 .unthrottle = hvc_unthrottle,
879 .write_room = hvc_write_room,
880 .chars_in_buffer = hvc_chars_in_buffer,
881 .tiocmget = hvc_tiocmget,
882 .tiocmset = hvc_tiocmset,
883 #ifdef CONFIG_CONSOLE_POLL
884 .poll_init = hvc_poll_init,
885 .poll_get_char = hvc_poll_get_char,
886 .poll_put_char = hvc_poll_put_char,
890 static const struct tty_port_operations hvc_port_ops = {
891 .destruct = hvc_port_destruct,
894 struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
895 const struct hv_ops *ops,
898 struct hvc_struct *hp;
901 /* We wait until a driver actually comes along */
902 if (atomic_inc_not_zero(&hvc_needs_init)) {
903 int err = hvc_init();
908 hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
911 return ERR_PTR(-ENOMEM);
913 hp->vtermno = vtermno;
916 hp->outbuf_size = outbuf_size;
917 hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
919 tty_port_init(&hp->port);
920 hp->port.ops = &hvc_port_ops;
922 INIT_WORK(&hp->tty_resize, hvc_set_winsz);
923 spin_lock_init(&hp->lock);
924 mutex_lock(&hvc_structs_mutex);
928 * see if this vterm id matches one registered for console.
930 for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
931 if (vtermnos[i] == hp->vtermno &&
932 cons_ops[i] == hp->ops)
935 /* no matching slot, just use a counter */
936 if (i >= MAX_NR_HVC_CONSOLES)
941 vtermnos[i] = vtermno;
943 list_add_tail(&(hp->next), &hvc_structs);
944 mutex_unlock(&hvc_structs_mutex);
946 /* check if we need to re-register the kernel console */
947 hvc_check_console(i);
951 EXPORT_SYMBOL_GPL(hvc_alloc);
953 int hvc_remove(struct hvc_struct *hp)
956 struct tty_struct *tty;
958 tty = tty_port_tty_get(&hp->port);
961 spin_lock_irqsave(&hp->lock, flags);
962 if (hp->index < MAX_NR_HVC_CONSOLES) {
963 vtermnos[hp->index] = -1;
964 cons_ops[hp->index] = NULL;
967 /* Don't whack hp->irq because tty_hangup() will need to free the irq. */
969 spin_unlock_irqrestore(&hp->lock, flags);
973 * We 'put' the instance that was grabbed when the kref instance
974 * was initialized using kref_init(). Let the last holder of this
975 * kref cause it to be removed, which will probably be the tty_vhangup
978 tty_port_put(&hp->port);
981 * This function call will auto chain call hvc_hangup.
989 EXPORT_SYMBOL_GPL(hvc_remove);
991 /* Driver initialization: called as soon as someone uses hvc_alloc(). */
992 static int hvc_init(void)
994 struct tty_driver *drv;
997 /* We need more than hvc_count adapters due to hotplug additions. */
998 drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
1004 drv->driver_name = "hvc";
1006 drv->major = HVC_MAJOR;
1007 drv->minor_start = HVC_MINOR;
1008 drv->type = TTY_DRIVER_TYPE_SYSTEM;
1009 drv->init_termios = tty_std_termios;
1010 drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_RESET_TERMIOS;
1011 tty_set_operations(drv, &hvc_ops);
1013 /* Always start the kthread because there can be hotplug vty adapters
1015 hvc_task = kthread_run(khvcd, NULL, "khvcd");
1016 if (IS_ERR(hvc_task)) {
1017 printk(KERN_ERR "Couldn't create kthread for console.\n");
1018 err = PTR_ERR(hvc_task);
1022 err = tty_register_driver(drv);
1024 printk(KERN_ERR "Couldn't register hvc console driver\n");
1029 * Make sure tty is fully registered before allowing it to be
1030 * found by hvc_console_device.
1037 kthread_stop(hvc_task);
1040 put_tty_driver(drv);