1// SPDX-License-Identifier: GPL-2.0+
2/*
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
7 *
8 * Additional Author(s):
9 *  Ryan S. Arnold <rsa@us.ibm.com>
10 */
11
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>
30
31#include <linux/uaccess.h>
32
33#include "hvc_console.h"
34
35#define HVC_MAJOR	229
36#define HVC_MINOR	0
37
38/*
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.
41 */
42#define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
43
44/*
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.
48 */
49#define N_OUTBUF	16
50#define N_INBUF		16
51
52#define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES)))
53
54static struct tty_driver *hvc_driver;
55static struct task_struct *hvc_task;
56
57/* Picks up late kicks after list walk but before schedule() */
58static int hvc_kicked;
59
60/* hvc_init is triggered from hvc_alloc, i.e. only when actually used */
61static atomic_t hvc_needs_init __read_mostly = ATOMIC_INIT(-1);
62
63static int hvc_init(void);
64
65#ifdef CONFIG_MAGIC_SYSRQ
66static int sysrq_pressed;
67#endif
68
69/* dynamic list of hvc_struct instances */
70static LIST_HEAD(hvc_structs);
71
72/*
73 * Protect the list of hvc_struct instances from inserts and removals during
74 * list traversal.
75 */
76static DEFINE_MUTEX(hvc_structs_mutex);
77
78/*
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().
82 */
83static int last_hvc = -1;
84
85/*
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.
89 */
90static struct hvc_struct *hvc_get_by_index(int index)
91{
92	struct hvc_struct *hp;
93	unsigned long flags;
94
95	mutex_lock(&hvc_structs_mutex);
96
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);
103			return hp;
104		}
105		spin_unlock_irqrestore(&hp->lock, flags);
106	}
107	hp = NULL;
108	mutex_unlock(&hvc_structs_mutex);
109
110	return hp;
111}
112
113static int __hvc_flush(const struct hv_ops *ops, uint32_t vtermno, bool wait)
114{
115	if (wait)
116		might_sleep();
117
118	if (ops->flush)
119		return ops->flush(vtermno, wait);
120	return 0;
121}
122
123static int hvc_console_flush(const struct hv_ops *ops, uint32_t vtermno)
124{
125	return __hvc_flush(ops, vtermno, false);
126}
127
128/*
129 * Wait for the console to flush before writing more to it. This sleeps.
130 */
131static int hvc_flush(struct hvc_struct *hp)
132{
133	return __hvc_flush(hp->ops, hp->vtermno, true);
134}
135
136/*
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.
141 */
142static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
143static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
144	{[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
145
146/*
147 * Console APIs, NOT TTY.  These APIs are available immediately when
148 * hvc_console_setup() finds adapters.
149 */
150
151static void hvc_console_print(struct console *co, const char *b,
152			      unsigned count)
153{
154	char c[N_OUTBUF] __ALIGNED__;
155	unsigned i = 0, n = 0;
156	int r, donecr = 0, index = co->index;
157
158	/* Console access attempt outside of acceptable console range. */
159	if (index >= MAX_NR_HVC_CONSOLES)
160		return;
161
162	/* This console adapter was removed so it is not usable. */
163	if (vtermnos[index] == -1)
164		return;
165
166	while (count > 0 || i > 0) {
167		if (count > 0 && i < sizeof(c)) {
168			if (b[n] == '\n' && !donecr) {
169				c[i++] = '\r';
170				donecr = 1;
171			} else {
172				c[i++] = b[n++];
173				donecr = 0;
174				--count;
175			}
176		} else {
177			r = cons_ops[index]->put_chars(vtermnos[index], c, i);
178			if (r <= 0) {
179				/* throw away characters on error
180				 * but spin in case of -EAGAIN */
181				if (r != -EAGAIN) {
182					i = 0;
183				} else {
184					hvc_console_flush(cons_ops[index],
185						      vtermnos[index]);
186				}
187			} else if (r > 0) {
188				i -= r;
189				if (i > 0)
190					memmove(c, c+r, i);
191			}
192		}
193	}
194	hvc_console_flush(cons_ops[index], vtermnos[index]);
195}
196
197static struct tty_driver *hvc_console_device(struct console *c, int *index)
198{
199	if (vtermnos[c->index] == -1)
200		return NULL;
201
202	*index = c->index;
203	return hvc_driver;
204}
205
206static int hvc_console_setup(struct console *co, char *options)
207{
208	if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
209		return -ENODEV;
210
211	if (vtermnos[co->index] == -1)
212		return -ENODEV;
213
214	return 0;
215}
216
217static struct console hvc_console = {
218	.name		= "hvc",
219	.write		= hvc_console_print,
220	.device		= hvc_console_device,
221	.setup		= hvc_console_setup,
222	.flags		= CON_PRINTBUFFER,
223	.index		= -1,
224};
225
226/*
227 * Early console initialization.  Precedes driver initialization.
228 *
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
237 *
238 * Note that for cases 2 and 3, we will match later when the io driver
239 * calls hvc_instantiate() and call register again.
240 */
241static int __init hvc_console_init(void)
242{
243	register_console(&hvc_console);
244	return 0;
245}
246console_initcall(hvc_console_init);
247
248/* callback when the kboject ref count reaches zero. */
249static void hvc_port_destruct(struct tty_port *port)
250{
251	struct hvc_struct *hp = container_of(port, struct hvc_struct, port);
252	unsigned long flags;
253
254	mutex_lock(&hvc_structs_mutex);
255
256	spin_lock_irqsave(&hp->lock, flags);
257	list_del(&(hp->next));
258	spin_unlock_irqrestore(&hp->lock, flags);
259
260	mutex_unlock(&hvc_structs_mutex);
261
262	kfree(hp);
263}
264
265static void hvc_check_console(int index)
266{
267	/* Already registered, bail out */
268	if (console_is_registered(&hvc_console))
269		return;
270
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.
274	 */
275	if (index == hvc_console.index)
276		register_console(&hvc_console);
277}
278
279/*
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.
284 */
285int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
286{
287	struct hvc_struct *hp;
288
289	if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
290		return -1;
291
292	if (vtermnos[index] != -1)
293		return -1;
294
295	/* make sure no tty has been registered in this index */
296	hp = hvc_get_by_index(index);
297	if (hp) {
298		tty_port_put(&hp->port);
299		return -1;
300	}
301
302	vtermnos[index] = vtermno;
303	cons_ops[index] = ops;
304
305	/* check if we need to re-register the kernel console */
306	hvc_check_console(index);
307
308	return 0;
309}
310EXPORT_SYMBOL_GPL(hvc_instantiate);
311
312/* Wake the sleeping khvcd */
313void hvc_kick(void)
314{
315	hvc_kicked = 1;
316	wake_up_process(hvc_task);
317}
318EXPORT_SYMBOL_GPL(hvc_kick);
319
320static void hvc_unthrottle(struct tty_struct *tty)
321{
322	hvc_kick();
323}
324
325static int hvc_install(struct tty_driver *driver, struct tty_struct *tty)
326{
327	struct hvc_struct *hp;
328	int rc;
329
330	/* Auto increments kref reference if found. */
331	hp = hvc_get_by_index(tty->index);
332	if (!hp)
333		return -ENODEV;
334
335	tty->driver_data = hp;
336
337	rc = tty_port_install(&hp->port, driver, tty);
338	if (rc)
339		tty_port_put(&hp->port);
340	return rc;
341}
342
343/*
344 * The TTY interface won't be used until after the vio layer has exposed the vty
345 * adapter to the kernel.
346 */
347static int hvc_open(struct tty_struct *tty, struct file * filp)
348{
349	struct hvc_struct *hp = tty->driver_data;
350	unsigned long flags;
351	int rc = 0;
352
353	spin_lock_irqsave(&hp->port.lock, flags);
354	/* Check and then increment for fast path open. */
355	if (hp->port.count++ > 0) {
356		spin_unlock_irqrestore(&hp->port.lock, flags);
357		hvc_kick();
358		return 0;
359	} /* else count == 0 */
360	spin_unlock_irqrestore(&hp->port.lock, flags);
361
362	tty_port_tty_set(&hp->port, tty);
363
364	if (hp->ops->notifier_add)
365		rc = hp->ops->notifier_add(hp, hp->data);
366
367	/*
368	 * If the notifier fails we return an error.  The tty layer
369	 * will call hvc_close() after a failed open but we don't want to clean
370	 * up there so we'll clean up here and clear out the previously set
371	 * tty fields and return the kref reference.
372	 */
373	if (rc) {
374		printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
375	} else {
376		/* We are ready... raise DTR/RTS */
377		if (C_BAUD(tty))
378			if (hp->ops->dtr_rts)
379				hp->ops->dtr_rts(hp, true);
380		tty_port_set_initialized(&hp->port, true);
381	}
382
383	/* Force wakeup of the polling thread */
384	hvc_kick();
385
386	return rc;
387}
388
389static void hvc_close(struct tty_struct *tty, struct file * filp)
390{
391	struct hvc_struct *hp = tty->driver_data;
392	unsigned long flags;
393
394	if (tty_hung_up_p(filp))
395		return;
396
397	spin_lock_irqsave(&hp->port.lock, flags);
398
399	if (--hp->port.count == 0) {
400		spin_unlock_irqrestore(&hp->port.lock, flags);
401		/* We are done with the tty pointer now. */
402		tty_port_tty_set(&hp->port, NULL);
403
404		if (!tty_port_initialized(&hp->port))
405			return;
406
407		if (C_HUPCL(tty))
408			if (hp->ops->dtr_rts)
409				hp->ops->dtr_rts(hp, false);
410
411		if (hp->ops->notifier_del)
412			hp->ops->notifier_del(hp, hp->data);
413
414		/* cancel pending tty resize work */
415		cancel_work_sync(&hp->tty_resize);
416
417		/*
418		 * Chain calls chars_in_buffer() and returns immediately if
419		 * there is no buffered data otherwise sleeps on a wait queue
420		 * waking periodically to check chars_in_buffer().
421		 */
422		tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
423		tty_port_set_initialized(&hp->port, false);
424	} else {
425		if (hp->port.count < 0)
426			printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
427				hp->vtermno, hp->port.count);
428		spin_unlock_irqrestore(&hp->port.lock, flags);
429	}
430}
431
432static void hvc_cleanup(struct tty_struct *tty)
433{
434	struct hvc_struct *hp = tty->driver_data;
435
436	tty_port_put(&hp->port);
437}
438
439static void hvc_hangup(struct tty_struct *tty)
440{
441	struct hvc_struct *hp = tty->driver_data;
442	unsigned long flags;
443
444	if (!hp)
445		return;
446
447	/* cancel pending tty resize work */
448	cancel_work_sync(&hp->tty_resize);
449
450	spin_lock_irqsave(&hp->port.lock, flags);
451
452	/*
453	 * The N_TTY line discipline has problems such that in a close vs
454	 * open->hangup case this can be called after the final close so prevent
455	 * that from happening for now.
456	 */
457	if (hp->port.count <= 0) {
458		spin_unlock_irqrestore(&hp->port.lock, flags);
459		return;
460	}
461
462	hp->port.count = 0;
463	spin_unlock_irqrestore(&hp->port.lock, flags);
464	tty_port_tty_set(&hp->port, NULL);
465
466	hp->n_outbuf = 0;
467
468	if (hp->ops->notifier_hangup)
469		hp->ops->notifier_hangup(hp, hp->data);
470}
471
472/*
473 * Push buffered characters whether they were just recently buffered or waiting
474 * on a blocked hypervisor.  Call this function with hp->lock held.
475 */
476static int hvc_push(struct hvc_struct *hp)
477{
478	int n;
479
480	n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
481	if (n <= 0) {
482		if (n == 0 || n == -EAGAIN) {
483			hp->do_wakeup = 1;
484			return 0;
485		}
486		/* throw away output on error; this happens when
487		   there is no session connected to the vterm. */
488		hp->n_outbuf = 0;
489	} else
490		hp->n_outbuf -= n;
491	if (hp->n_outbuf > 0)
492		memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
493	else
494		hp->do_wakeup = 1;
495
496	return n;
497}
498
499static ssize_t hvc_write(struct tty_struct *tty, const u8 *buf, size_t count)
500{
501	struct hvc_struct *hp = tty->driver_data;
502	unsigned long flags;
503	size_t rsize, written = 0;
504
505	/* This write was probably executed during a tty close. */
506	if (!hp)
507		return -EPIPE;
508
509	/* FIXME what's this (unprotected) check for? */
510	if (hp->port.count <= 0)
511		return -EIO;
512
513	while (count > 0) {
514		int ret = 0;
515
516		spin_lock_irqsave(&hp->lock, flags);
517
518		rsize = hp->outbuf_size - hp->n_outbuf;
519
520		if (rsize) {
521			if (rsize > count)
522				rsize = count;
523			memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
524			count -= rsize;
525			buf += rsize;
526			hp->n_outbuf += rsize;
527			written += rsize;
528		}
529
530		if (hp->n_outbuf > 0)
531			ret = hvc_push(hp);
532
533		spin_unlock_irqrestore(&hp->lock, flags);
534
535		if (!ret)
536			break;
537
538		if (count) {
539			if (hp->n_outbuf > 0)
540				hvc_flush(hp);
541			cond_resched();
542		}
543	}
544
545	/*
546	 * Racy, but harmless, kick thread if there is still pending data.
547	 */
548	if (hp->n_outbuf)
549		hvc_kick();
550
551	return written;
552}
553
554/**
555 * hvc_set_winsz() - Resize the hvc tty terminal window.
556 * @work:	work structure.
557 *
558 * The routine shall not be called within an atomic context because it
559 * might sleep.
560 *
561 * Locking:	hp->lock
562 */
563static void hvc_set_winsz(struct work_struct *work)
564{
565	struct hvc_struct *hp;
566	unsigned long hvc_flags;
567	struct tty_struct *tty;
568	struct winsize ws;
569
570	hp = container_of(work, struct hvc_struct, tty_resize);
571
572	tty = tty_port_tty_get(&hp->port);
573	if (!tty)
574		return;
575
576	spin_lock_irqsave(&hp->lock, hvc_flags);
577	ws = hp->ws;
578	spin_unlock_irqrestore(&hp->lock, hvc_flags);
579
580	tty_do_resize(tty, &ws);
581	tty_kref_put(tty);
582}
583
584/*
585 * This is actually a contract between the driver and the tty layer outlining
586 * how much write room the driver can guarantee will be sent OR BUFFERED.  This
587 * driver MUST honor the return value.
588 */
589static unsigned int hvc_write_room(struct tty_struct *tty)
590{
591	struct hvc_struct *hp = tty->driver_data;
592
593	if (!hp)
594		return 0;
595
596	return hp->outbuf_size - hp->n_outbuf;
597}
598
599static unsigned int hvc_chars_in_buffer(struct tty_struct *tty)
600{
601	struct hvc_struct *hp = tty->driver_data;
602
603	if (!hp)
604		return 0;
605	return hp->n_outbuf;
606}
607
608/*
609 * timeout will vary between the MIN and MAX values defined here.  By default
610 * and during console activity we will use a default MIN_TIMEOUT of 10.  When
611 * the console is idle, we increase the timeout value on each pass through
612 * msleep until we reach the max.  This may be noticeable as a brief (average
613 * one second) delay on the console before the console responds to input when
614 * there has been no input for some time.
615 */
616#define MIN_TIMEOUT		(10)
617#define MAX_TIMEOUT		(2000)
618static u32 timeout = MIN_TIMEOUT;
619
620/*
621 * Maximum number of bytes to get from the console driver if hvc_poll is
622 * called from driver (and can't sleep). Any more than this and we break
623 * and start polling with khvcd. This value was derived from an OpenBMC
624 * console with the OPAL driver that results in about 0.25ms interrupts off
625 * latency.
626 */
627#define HVC_ATOMIC_READ_MAX	128
628
629#define HVC_POLL_READ	0x00000001
630#define HVC_POLL_WRITE	0x00000002
631
632static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
633{
634	struct tty_struct *tty;
635	int i, n, count, poll_mask = 0;
636	char buf[N_INBUF] __ALIGNED__;
637	unsigned long flags;
638	int read_total = 0;
639	int written_total = 0;
640
641	spin_lock_irqsave(&hp->lock, flags);
642
643	/* Push pending writes */
644	if (hp->n_outbuf > 0)
645		written_total = hvc_push(hp);
646
647	/* Reschedule us if still some write pending */
648	if (hp->n_outbuf > 0) {
649		poll_mask |= HVC_POLL_WRITE;
650		/* If hvc_push() was not able to write, sleep a few msecs */
651		timeout = (written_total) ? 0 : MIN_TIMEOUT;
652	}
653
654	if (may_sleep) {
655		spin_unlock_irqrestore(&hp->lock, flags);
656		cond_resched();
657		spin_lock_irqsave(&hp->lock, flags);
658	}
659
660	/* No tty attached, just skip */
661	tty = tty_port_tty_get(&hp->port);
662	if (tty == NULL)
663		goto bail;
664
665	/* Now check if we can get data (are we throttled ?) */
666	if (tty_throttled(tty))
667		goto out;
668
669	/* If we aren't notifier driven and aren't throttled, we always
670	 * request a reschedule
671	 */
672	if (!hp->irq_requested)
673		poll_mask |= HVC_POLL_READ;
674
675 read_again:
676	/* Read data if any */
677	count = tty_buffer_request_room(&hp->port, N_INBUF);
678
679	/* If flip is full, just reschedule a later read */
680	if (count == 0) {
681		poll_mask |= HVC_POLL_READ;
682		goto out;
683	}
684
685	n = hp->ops->get_chars(hp->vtermno, buf, count);
686	if (n <= 0) {
687		/* Hangup the tty when disconnected from host */
688		if (n == -EPIPE) {
689			spin_unlock_irqrestore(&hp->lock, flags);
690			tty_hangup(tty);
691			spin_lock_irqsave(&hp->lock, flags);
692		} else if ( n == -EAGAIN ) {
693			/*
694			 * Some back-ends can only ensure a certain min
695			 * num of bytes read, which may be > 'count'.
696			 * Let the tty clear the flip buff to make room.
697			 */
698			poll_mask |= HVC_POLL_READ;
699		}
700		goto out;
701	}
702
703	for (i = 0; i < n; ++i) {
704#ifdef CONFIG_MAGIC_SYSRQ
705		if (hp->index == hvc_console.index) {
706			/* Handle the SysRq Hack */
707			/* XXX should support a sequence */
708			if (buf[i] == '\x0f') {	/* ^O */
709				/* if ^O is pressed again, reset
710				 * sysrq_pressed and flip ^O char */
711				sysrq_pressed = !sysrq_pressed;
712				if (sysrq_pressed)
713					continue;
714			} else if (sysrq_pressed) {
715				handle_sysrq(buf[i]);
716				sysrq_pressed = 0;
717				continue;
718			}
719		}
720#endif /* CONFIG_MAGIC_SYSRQ */
721		tty_insert_flip_char(&hp->port, buf[i], 0);
722	}
723	read_total += n;
724
725	if (may_sleep) {
726		/* Keep going until the flip is full */
727		spin_unlock_irqrestore(&hp->lock, flags);
728		cond_resched();
729		spin_lock_irqsave(&hp->lock, flags);
730		goto read_again;
731	} else if (read_total < HVC_ATOMIC_READ_MAX) {
732		/* Break and defer if it's a large read in atomic */
733		goto read_again;
734	}
735
736	/*
737	 * Latency break, schedule another poll immediately.
738	 */
739	poll_mask |= HVC_POLL_READ;
740
741 out:
742	/* Wakeup write queue if necessary */
743	if (hp->do_wakeup) {
744		hp->do_wakeup = 0;
745		tty_wakeup(tty);
746	}
747 bail:
748	spin_unlock_irqrestore(&hp->lock, flags);
749
750	if (read_total) {
751		/* Activity is occurring, so reset the polling backoff value to
752		   a minimum for performance. */
753		timeout = MIN_TIMEOUT;
754
755		tty_flip_buffer_push(&hp->port);
756	}
757	tty_kref_put(tty);
758
759	return poll_mask;
760}
761
762int hvc_poll(struct hvc_struct *hp)
763{
764	return __hvc_poll(hp, false);
765}
766EXPORT_SYMBOL_GPL(hvc_poll);
767
768/**
769 * __hvc_resize() - Update terminal window size information.
770 * @hp:		HVC console pointer
771 * @ws:		Terminal window size structure
772 *
773 * Stores the specified window size information in the hvc structure of @hp.
774 * The function schedule the tty resize update.
775 *
776 * Locking:	Locking free; the function MUST be called holding hp->lock
777 */
778void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
779{
780	hp->ws = ws;
781	schedule_work(&hp->tty_resize);
782}
783EXPORT_SYMBOL_GPL(__hvc_resize);
784
785/*
786 * This kthread is either polling or interrupt driven.  This is determined by
787 * calling hvc_poll() who determines whether a console adapter support
788 * interrupts.
789 */
790static int khvcd(void *unused)
791{
792	int poll_mask;
793	struct hvc_struct *hp;
794
795	set_freezable();
796	do {
797		poll_mask = 0;
798		hvc_kicked = 0;
799		try_to_freeze();
800		wmb();
801		if (!cpus_are_in_xmon()) {
802			mutex_lock(&hvc_structs_mutex);
803			list_for_each_entry(hp, &hvc_structs, next) {
804				poll_mask |= __hvc_poll(hp, true);
805				cond_resched();
806			}
807			mutex_unlock(&hvc_structs_mutex);
808		} else
809			poll_mask |= HVC_POLL_READ;
810		if (hvc_kicked)
811			continue;
812		set_current_state(TASK_INTERRUPTIBLE);
813		if (!hvc_kicked) {
814			if (poll_mask == 0)
815				schedule();
816			else {
817				unsigned long j_timeout;
818
819				if (timeout < MAX_TIMEOUT)
820					timeout += (timeout >> 6) + 1;
821
822				/*
823				 * We don't use msleep_interruptible otherwise
824				 * "kick" will fail to wake us up
825				 */
826				j_timeout = msecs_to_jiffies(timeout) + 1;
827				schedule_timeout_interruptible(j_timeout);
828			}
829		}
830		__set_current_state(TASK_RUNNING);
831	} while (!kthread_should_stop());
832
833	return 0;
834}
835
836static int hvc_tiocmget(struct tty_struct *tty)
837{
838	struct hvc_struct *hp = tty->driver_data;
839
840	if (!hp || !hp->ops->tiocmget)
841		return -EINVAL;
842	return hp->ops->tiocmget(hp);
843}
844
845static int hvc_tiocmset(struct tty_struct *tty,
846			unsigned int set, unsigned int clear)
847{
848	struct hvc_struct *hp = tty->driver_data;
849
850	if (!hp || !hp->ops->tiocmset)
851		return -EINVAL;
852	return hp->ops->tiocmset(hp, set, clear);
853}
854
855#ifdef CONFIG_CONSOLE_POLL
856static int hvc_poll_init(struct tty_driver *driver, int line, char *options)
857{
858	return 0;
859}
860
861static int hvc_poll_get_char(struct tty_driver *driver, int line)
862{
863	struct tty_struct *tty = driver->ttys[0];
864	struct hvc_struct *hp = tty->driver_data;
865	int n;
866	char ch;
867
868	n = hp->ops->get_chars(hp->vtermno, &ch, 1);
869
870	if (n <= 0)
871		return NO_POLL_CHAR;
872
873	return ch;
874}
875
876static void hvc_poll_put_char(struct tty_driver *driver, int line, char ch)
877{
878	struct tty_struct *tty = driver->ttys[0];
879	struct hvc_struct *hp = tty->driver_data;
880	int n;
881
882	do {
883		n = hp->ops->put_chars(hp->vtermno, &ch, 1);
884	} while (n <= 0);
885}
886#endif
887
888static const struct tty_operations hvc_ops = {
889	.install = hvc_install,
890	.open = hvc_open,
891	.close = hvc_close,
892	.cleanup = hvc_cleanup,
893	.write = hvc_write,
894	.hangup = hvc_hangup,
895	.unthrottle = hvc_unthrottle,
896	.write_room = hvc_write_room,
897	.chars_in_buffer = hvc_chars_in_buffer,
898	.tiocmget = hvc_tiocmget,
899	.tiocmset = hvc_tiocmset,
900#ifdef CONFIG_CONSOLE_POLL
901	.poll_init = hvc_poll_init,
902	.poll_get_char = hvc_poll_get_char,
903	.poll_put_char = hvc_poll_put_char,
904#endif
905};
906
907static const struct tty_port_operations hvc_port_ops = {
908	.destruct = hvc_port_destruct,
909};
910
911struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
912			     const struct hv_ops *ops,
913			     int outbuf_size)
914{
915	struct hvc_struct *hp;
916	int i;
917
918	/* We wait until a driver actually comes along */
919	if (atomic_inc_not_zero(&hvc_needs_init)) {
920		int err = hvc_init();
921		if (err)
922			return ERR_PTR(err);
923	}
924
925	hp = kzalloc(struct_size(hp, outbuf, outbuf_size), GFP_KERNEL);
926	if (!hp)
927		return ERR_PTR(-ENOMEM);
928
929	hp->vtermno = vtermno;
930	hp->data = data;
931	hp->ops = ops;
932	hp->outbuf_size = outbuf_size;
933
934	tty_port_init(&hp->port);
935	hp->port.ops = &hvc_port_ops;
936
937	INIT_WORK(&hp->tty_resize, hvc_set_winsz);
938	spin_lock_init(&hp->lock);
939	mutex_lock(&hvc_structs_mutex);
940
941	/*
942	 * find index to use:
943	 * see if this vterm id matches one registered for console.
944	 */
945	for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
946		if (vtermnos[i] == hp->vtermno &&
947		    cons_ops[i] == hp->ops)
948			break;
949
950	if (i >= MAX_NR_HVC_CONSOLES) {
951
952		/* find 'empty' slot for console */
953		for (i = 0; i < MAX_NR_HVC_CONSOLES && vtermnos[i] != -1; i++) {
954		}
955
956		/* no matching slot, just use a counter */
957		if (i == MAX_NR_HVC_CONSOLES)
958			i = ++last_hvc + MAX_NR_HVC_CONSOLES;
959	}
960
961	hp->index = i;
962	if (i < MAX_NR_HVC_CONSOLES) {
963		cons_ops[i] = ops;
964		vtermnos[i] = vtermno;
965	}
966
967	list_add_tail(&(hp->next), &hvc_structs);
968	mutex_unlock(&hvc_structs_mutex);
969
970	/* check if we need to re-register the kernel console */
971	hvc_check_console(i);
972
973	return hp;
974}
975EXPORT_SYMBOL_GPL(hvc_alloc);
976
977void hvc_remove(struct hvc_struct *hp)
978{
979	unsigned long flags;
980	struct tty_struct *tty;
981
982	tty = tty_port_tty_get(&hp->port);
983
984	console_lock();
985	spin_lock_irqsave(&hp->lock, flags);
986	if (hp->index < MAX_NR_HVC_CONSOLES) {
987		vtermnos[hp->index] = -1;
988		cons_ops[hp->index] = NULL;
989	}
990
991	/* Don't whack hp->irq because tty_hangup() will need to free the irq. */
992
993	spin_unlock_irqrestore(&hp->lock, flags);
994	console_unlock();
995
996	/*
997	 * We 'put' the instance that was grabbed when the kref instance
998	 * was initialized using kref_init().  Let the last holder of this
999	 * kref cause it to be removed, which will probably be the tty_vhangup
1000	 * below.
1001	 */
1002	tty_port_put(&hp->port);
1003
1004	/*
1005	 * This function call will auto chain call hvc_hangup.
1006	 */
1007	if (tty) {
1008		tty_vhangup(tty);
1009		tty_kref_put(tty);
1010	}
1011}
1012EXPORT_SYMBOL_GPL(hvc_remove);
1013
1014/* Driver initialization: called as soon as someone uses hvc_alloc(). */
1015static int hvc_init(void)
1016{
1017	struct tty_driver *drv;
1018	int err;
1019
1020	/* We need more than hvc_count adapters due to hotplug additions. */
1021	drv = tty_alloc_driver(HVC_ALLOC_TTY_ADAPTERS, TTY_DRIVER_REAL_RAW |
1022			TTY_DRIVER_RESET_TERMIOS);
1023	if (IS_ERR(drv)) {
1024		err = PTR_ERR(drv);
1025		goto out;
1026	}
1027
1028	drv->driver_name = "hvc";
1029	drv->name = "hvc";
1030	drv->major = HVC_MAJOR;
1031	drv->minor_start = HVC_MINOR;
1032	drv->type = TTY_DRIVER_TYPE_SYSTEM;
1033	drv->init_termios = tty_std_termios;
1034	tty_set_operations(drv, &hvc_ops);
1035
1036	/* Always start the kthread because there can be hotplug vty adapters
1037	 * added later. */
1038	hvc_task = kthread_run(khvcd, NULL, "khvcd");
1039	if (IS_ERR(hvc_task)) {
1040		printk(KERN_ERR "Couldn't create kthread for console.\n");
1041		err = PTR_ERR(hvc_task);
1042		goto put_tty;
1043	}
1044
1045	err = tty_register_driver(drv);
1046	if (err) {
1047		printk(KERN_ERR "Couldn't register hvc console driver\n");
1048		goto stop_thread;
1049	}
1050
1051	/*
1052	 * Make sure tty is fully registered before allowing it to be
1053	 * found by hvc_console_device.
1054	 */
1055	smp_mb();
1056	hvc_driver = drv;
1057	return 0;
1058
1059stop_thread:
1060	kthread_stop(hvc_task);
1061	hvc_task = NULL;
1062put_tty:
1063	tty_driver_kref_put(drv);
1064out:
1065	return err;
1066}
1067