cc2cd46bedc6ac6dac8dd7d256a3605c784128cf
[linux-2.6.git] / drivers / char / hvc_console.c
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
6  *
7  * Additional Author(s):
8  *  Ryan S. Arnold <rsa@us.ibm.com>
9  *
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.
14  * 
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.
19  * 
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
23  */
24
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/kobject.h>
31 #include <linux/kthread.h>
32 #include <linux/list.h>
33 #include <linux/module.h>
34 #include <linux/major.h>
35 #include <linux/sysrq.h>
36 #include <linux/tty.h>
37 #include <linux/tty_flip.h>
38 #include <linux/sched.h>
39 #include <linux/spinlock.h>
40 #include <linux/delay.h>
41 #include <linux/freezer.h>
42
43 #include <asm/uaccess.h>
44
45 #include "hvc_console.h"
46
47 #define HVC_MAJOR       229
48 #define HVC_MINOR       0
49
50 #define TIMEOUT         (10)
51
52 /*
53  * Wait this long per iteration while trying to push buffered data to the
54  * hypervisor before allowing the tty to complete a close operation.
55  */
56 #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
57
58 /*
59  * These sizes are most efficient for vio, because they are the
60  * native transfer size. We could make them selectable in the
61  * future to better deal with backends that want other buffer sizes.
62  */
63 #define N_OUTBUF        16
64 #define N_INBUF         16
65
66 #define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
67
68 static struct tty_driver *hvc_driver;
69 static struct task_struct *hvc_task;
70
71 /* Picks up late kicks after list walk but before schedule() */
72 static int hvc_kicked;
73
74 #ifdef CONFIG_MAGIC_SYSRQ
75 static int sysrq_pressed;
76 #endif
77
78 struct hvc_struct {
79         spinlock_t lock;
80         int index;
81         struct tty_struct *tty;
82         unsigned int count;
83         int do_wakeup;
84         char *outbuf;
85         int outbuf_size;
86         int n_outbuf;
87         uint32_t vtermno;
88         struct hv_ops *ops;
89         int irq_requested;
90         int irq;
91         struct list_head next;
92         struct kobject kobj; /* ref count & hvc_struct lifetime */
93 };
94
95 /* dynamic list of hvc_struct instances */
96 static struct list_head hvc_structs = LIST_HEAD_INIT(hvc_structs);
97
98 /*
99  * Protect the list of hvc_struct instances from inserts and removals during
100  * list traversal.
101  */
102 static DEFINE_SPINLOCK(hvc_structs_lock);
103
104 /*
105  * This value is used to assign a tty->index value to a hvc_struct based
106  * upon order of exposure via hvc_probe(), when we can not match it to
107  * a console canidate registered with hvc_instantiate().
108  */
109 static int last_hvc = -1;
110
111 /*
112  * Do not call this function with either the hvc_strucst_lock or the hvc_struct
113  * lock held.  If successful, this function increments the kobject reference
114  * count against the target hvc_struct so it should be released when finished.
115  */
116 struct hvc_struct *hvc_get_by_index(int index)
117 {
118         struct hvc_struct *hp;
119         unsigned long flags;
120
121         spin_lock(&hvc_structs_lock);
122
123         list_for_each_entry(hp, &hvc_structs, next) {
124                 spin_lock_irqsave(&hp->lock, flags);
125                 if (hp->index == index) {
126                         kobject_get(&hp->kobj);
127                         spin_unlock_irqrestore(&hp->lock, flags);
128                         spin_unlock(&hvc_structs_lock);
129                         return hp;
130                 }
131                 spin_unlock_irqrestore(&hp->lock, flags);
132         }
133         hp = NULL;
134
135         spin_unlock(&hvc_structs_lock);
136         return hp;
137 }
138
139
140 /*
141  * Initial console vtermnos for console API usage prior to full console
142  * initialization.  Any vty adapter outside this range will not have usable
143  * console interfaces but can still be used as a tty device.  This has to be
144  * static because kmalloc will not work during early console init.
145  */
146 static struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
147 static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
148         {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
149
150 /*
151  * Console APIs, NOT TTY.  These APIs are available immediately when
152  * hvc_console_setup() finds adapters.
153  */
154
155 void hvc_console_print(struct console *co, const char *b, unsigned count)
156 {
157         char c[N_OUTBUF] __ALIGNED__;
158         unsigned i = 0, n = 0;
159         int r, donecr = 0, index = co->index;
160
161         /* Console access attempt outside of acceptable console range. */
162         if (index >= MAX_NR_HVC_CONSOLES)
163                 return;
164
165         /* This console adapter was removed so it is not useable. */
166         if (vtermnos[index] < 0)
167                 return;
168
169         while (count > 0 || i > 0) {
170                 if (count > 0 && i < sizeof(c)) {
171                         if (b[n] == '\n' && !donecr) {
172                                 c[i++] = '\r';
173                                 donecr = 1;
174                         } else {
175                                 c[i++] = b[n++];
176                                 donecr = 0;
177                                 --count;
178                         }
179                 } else {
180                         r = cons_ops[index]->put_chars(vtermnos[index], c, i);
181                         if (r < 0) {
182                                 /* throw away chars on error */
183                                 i = 0;
184                         } else if (r > 0) {
185                                 i -= r;
186                                 if (i > 0)
187                                         memmove(c, c+r, i);
188                         }
189                 }
190         }
191 }
192
193 static struct tty_driver *hvc_console_device(struct console *c, int *index)
194 {
195         if (vtermnos[c->index] == -1)
196                 return NULL;
197
198         *index = c->index;
199         return hvc_driver;
200 }
201
202 static int __init hvc_console_setup(struct console *co, char *options)
203 {
204         if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
205                 return -ENODEV;
206
207         if (vtermnos[co->index] == -1)
208                 return -ENODEV;
209
210         return 0;
211 }
212
213 struct console hvc_con_driver = {
214         .name           = "hvc",
215         .write          = hvc_console_print,
216         .device         = hvc_console_device,
217         .setup          = hvc_console_setup,
218         .flags          = CON_PRINTBUFFER,
219         .index          = -1,
220 };
221
222 /*
223  * Early console initialization.  Preceeds driver initialization.
224  *
225  * (1) we are first, and the user specified another driver
226  * -- index will remain -1
227  * (2) we are first and the user specified no driver
228  * -- index will be set to 0, then we will fail setup.
229  * (3)  we are first and the user specified our driver
230  * -- index will be set to user specified driver, and we will fail
231  * (4) we are after driver, and this initcall will register us
232  * -- if the user didn't specify a driver then the console will match
233  *
234  * Note that for cases 2 and 3, we will match later when the io driver
235  * calls hvc_instantiate() and call register again.
236  */
237 static int __init hvc_console_init(void)
238 {
239         register_console(&hvc_con_driver);
240         return 0;
241 }
242 console_initcall(hvc_console_init);
243
244 /*
245  * hvc_instantiate() is an early console discovery method which locates
246  * consoles * prior to the vio subsystem discovering them.  Hotplugged
247  * vty adapters do NOT get an hvc_instantiate() callback since they
248  * appear after early console init.
249  */
250 int hvc_instantiate(uint32_t vtermno, int index, struct hv_ops *ops)
251 {
252         struct hvc_struct *hp;
253
254         if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
255                 return -1;
256
257         if (vtermnos[index] != -1)
258                 return -1;
259
260         /* make sure no no tty has been registerd in this index */
261         hp = hvc_get_by_index(index);
262         if (hp) {
263                 kobject_put(&hp->kobj);
264                 return -1;
265         }
266
267         vtermnos[index] = vtermno;
268         cons_ops[index] = ops;
269
270         /* reserve all indices upto and including this index */
271         if (last_hvc < index)
272                 last_hvc = index;
273
274         /* if this index is what the user requested, then register
275          * now (setup won't fail at this point).  It's ok to just
276          * call register again if previously .setup failed.
277          */
278         if (index == hvc_con_driver.index)
279                 register_console(&hvc_con_driver);
280
281         return 0;
282 }
283 EXPORT_SYMBOL(hvc_instantiate);
284
285 /* Wake the sleeping khvcd */
286 static void hvc_kick(void)
287 {
288         hvc_kicked = 1;
289         wake_up_process(hvc_task);
290 }
291
292 static int hvc_poll(struct hvc_struct *hp);
293
294 /*
295  * NOTE: This API isn't used if the console adapter doesn't support interrupts.
296  * In this case the console is poll driven.
297  */
298 static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance)
299 {
300         /* if hvc_poll request a repoll, then kick the hvcd thread */
301         if (hvc_poll(dev_instance))
302                 hvc_kick();
303         return IRQ_HANDLED;
304 }
305
306 static void hvc_unthrottle(struct tty_struct *tty)
307 {
308         hvc_kick();
309 }
310
311 /*
312  * The TTY interface won't be used until after the vio layer has exposed the vty
313  * adapter to the kernel.
314  */
315 static int hvc_open(struct tty_struct *tty, struct file * filp)
316 {
317         struct hvc_struct *hp;
318         unsigned long flags;
319         int irq = NO_IRQ;
320         int rc = 0;
321         struct kobject *kobjp;
322
323         /* Auto increments kobject reference if found. */
324         if (!(hp = hvc_get_by_index(tty->index)))
325                 return -ENODEV;
326
327         spin_lock_irqsave(&hp->lock, flags);
328         /* Check and then increment for fast path open. */
329         if (hp->count++ > 0) {
330                 spin_unlock_irqrestore(&hp->lock, flags);
331                 hvc_kick();
332                 return 0;
333         } /* else count == 0 */
334
335         tty->driver_data = hp;
336         tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */
337
338         hp->tty = tty;
339         /* Save for request_irq outside of spin_lock. */
340         irq = hp->irq;
341         if (irq != NO_IRQ)
342                 hp->irq_requested = 1;
343
344         kobjp = &hp->kobj;
345
346         spin_unlock_irqrestore(&hp->lock, flags);
347         /* check error, fallback to non-irq */
348         if (irq != NO_IRQ)
349                 rc = request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED, "hvc_console", hp);
350
351         /*
352          * If the request_irq() fails and we return an error.  The tty layer
353          * will call hvc_close() after a failed open but we don't want to clean
354          * up there so we'll clean up here and clear out the previously set
355          * tty fields and return the kobject reference.
356          */
357         if (rc) {
358                 spin_lock_irqsave(&hp->lock, flags);
359                 hp->tty = NULL;
360                 hp->irq_requested = 0;
361                 spin_unlock_irqrestore(&hp->lock, flags);
362                 tty->driver_data = NULL;
363                 kobject_put(kobjp);
364                 printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
365         }
366         /* Force wakeup of the polling thread */
367         hvc_kick();
368
369         return rc;
370 }
371
372 static void hvc_close(struct tty_struct *tty, struct file * filp)
373 {
374         struct hvc_struct *hp;
375         struct kobject *kobjp;
376         int irq = NO_IRQ;
377         unsigned long flags;
378
379         if (tty_hung_up_p(filp))
380                 return;
381
382         /*
383          * No driver_data means that this close was issued after a failed
384          * hvc_open by the tty layer's release_dev() function and we can just
385          * exit cleanly because the kobject reference wasn't made.
386          */
387         if (!tty->driver_data)
388                 return;
389
390         hp = tty->driver_data;
391         spin_lock_irqsave(&hp->lock, flags);
392
393         kobjp = &hp->kobj;
394         if (--hp->count == 0) {
395                 if (hp->irq_requested)
396                         irq = hp->irq;
397                 hp->irq_requested = 0;
398
399                 /* We are done with the tty pointer now. */
400                 hp->tty = NULL;
401                 spin_unlock_irqrestore(&hp->lock, flags);
402
403                 /*
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().
407                  */
408                 tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
409
410                 if (irq != NO_IRQ)
411                         free_irq(irq, hp);
412
413         } else {
414                 if (hp->count < 0)
415                         printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
416                                 hp->vtermno, hp->count);
417                 spin_unlock_irqrestore(&hp->lock, flags);
418         }
419
420         kobject_put(kobjp);
421 }
422
423 static void hvc_hangup(struct tty_struct *tty)
424 {
425         struct hvc_struct *hp = tty->driver_data;
426         unsigned long flags;
427         int irq = NO_IRQ;
428         int temp_open_count;
429         struct kobject *kobjp;
430
431         if (!hp)
432                 return;
433
434         spin_lock_irqsave(&hp->lock, flags);
435
436         /*
437          * The N_TTY line discipline has problems such that in a close vs
438          * open->hangup case this can be called after the final close so prevent
439          * that from happening for now.
440          */
441         if (hp->count <= 0) {
442                 spin_unlock_irqrestore(&hp->lock, flags);
443                 return;
444         }
445
446         kobjp = &hp->kobj;
447         temp_open_count = hp->count;
448         hp->count = 0;
449         hp->n_outbuf = 0;
450         hp->tty = NULL;
451         if (hp->irq_requested)
452                 /* Saved for use outside of spin_lock. */
453                 irq = hp->irq;
454         hp->irq_requested = 0;
455         spin_unlock_irqrestore(&hp->lock, flags);
456         if (irq != NO_IRQ)
457                 free_irq(irq, hp);
458         while(temp_open_count) {
459                 --temp_open_count;
460                 kobject_put(kobjp);
461         }
462 }
463
464 /*
465  * Push buffered characters whether they were just recently buffered or waiting
466  * on a blocked hypervisor.  Call this function with hp->lock held.
467  */
468 static void hvc_push(struct hvc_struct *hp)
469 {
470         int n;
471
472         n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
473         if (n <= 0) {
474                 if (n == 0) {
475                         hp->do_wakeup = 1;
476                         return;
477                 }
478                 /* throw away output on error; this happens when
479                    there is no session connected to the vterm. */
480                 hp->n_outbuf = 0;
481         } else
482                 hp->n_outbuf -= n;
483         if (hp->n_outbuf > 0)
484                 memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
485         else
486                 hp->do_wakeup = 1;
487 }
488
489 static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
490 {
491         struct hvc_struct *hp = tty->driver_data;
492         unsigned long flags;
493         int rsize, written = 0;
494
495         /* This write was probably executed during a tty close. */
496         if (!hp)
497                 return -EPIPE;
498
499         if (hp->count <= 0)
500                 return -EIO;
501
502         spin_lock_irqsave(&hp->lock, flags);
503
504         /* Push pending writes */
505         if (hp->n_outbuf > 0)
506                 hvc_push(hp);
507
508         while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
509                 if (rsize > count)
510                         rsize = count;
511                 memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
512                 count -= rsize;
513                 buf += rsize;
514                 hp->n_outbuf += rsize;
515                 written += rsize;
516                 hvc_push(hp);
517         }
518         spin_unlock_irqrestore(&hp->lock, flags);
519
520         /*
521          * Racy, but harmless, kick thread if there is still pending data.
522          */
523         if (hp->n_outbuf)
524                 hvc_kick();
525
526         return written;
527 }
528
529 /*
530  * This is actually a contract between the driver and the tty layer outlining
531  * how much write room the driver can guarentee will be sent OR BUFFERED.  This
532  * driver MUST honor the return value.
533  */
534 static int hvc_write_room(struct tty_struct *tty)
535 {
536         struct hvc_struct *hp = tty->driver_data;
537
538         if (!hp)
539                 return -1;
540
541         return hp->outbuf_size - hp->n_outbuf;
542 }
543
544 static int hvc_chars_in_buffer(struct tty_struct *tty)
545 {
546         struct hvc_struct *hp = tty->driver_data;
547
548         if (!hp)
549                 return -1;
550         return hp->n_outbuf;
551 }
552
553 #define HVC_POLL_READ   0x00000001
554 #define HVC_POLL_WRITE  0x00000002
555
556 static int hvc_poll(struct hvc_struct *hp)
557 {
558         struct tty_struct *tty;
559         int i, n, poll_mask = 0;
560         char buf[N_INBUF] __ALIGNED__;
561         unsigned long flags;
562         int read_total = 0;
563
564         spin_lock_irqsave(&hp->lock, flags);
565
566         /* Push pending writes */
567         if (hp->n_outbuf > 0)
568                 hvc_push(hp);
569
570         /* Reschedule us if still some write pending */
571         if (hp->n_outbuf > 0)
572                 poll_mask |= HVC_POLL_WRITE;
573
574         /* No tty attached, just skip */
575         tty = hp->tty;
576         if (tty == NULL)
577                 goto bail;
578
579         /* Now check if we can get data (are we throttled ?) */
580         if (test_bit(TTY_THROTTLED, &tty->flags))
581                 goto throttled;
582
583         /* If we aren't interrupt driven and aren't throttled, we always
584          * request a reschedule
585          */
586         if (hp->irq == NO_IRQ)
587                 poll_mask |= HVC_POLL_READ;
588
589         /* Read data if any */
590         for (;;) {
591                 int count = tty_buffer_request_room(tty, N_INBUF);
592
593                 /* If flip is full, just reschedule a later read */
594                 if (count == 0) {
595                         poll_mask |= HVC_POLL_READ;
596                         break;
597                 }
598
599                 n = hp->ops->get_chars(hp->vtermno, buf, count);
600                 if (n <= 0) {
601                         /* Hangup the tty when disconnected from host */
602                         if (n == -EPIPE) {
603                                 spin_unlock_irqrestore(&hp->lock, flags);
604                                 tty_hangup(tty);
605                                 spin_lock_irqsave(&hp->lock, flags);
606                         } else if ( n == -EAGAIN ) {
607                                 /*
608                                  * Some back-ends can only ensure a certain min
609                                  * num of bytes read, which may be > 'count'.
610                                  * Let the tty clear the flip buff to make room.
611                                  */
612                                 poll_mask |= HVC_POLL_READ;
613                         }
614                         break;
615                 }
616                 for (i = 0; i < n; ++i) {
617 #ifdef CONFIG_MAGIC_SYSRQ
618                         if (hp->index == hvc_con_driver.index) {
619                                 /* Handle the SysRq Hack */
620                                 /* XXX should support a sequence */
621                                 if (buf[i] == '\x0f') { /* ^O */
622                                         sysrq_pressed = 1;
623                                         continue;
624                                 } else if (sysrq_pressed) {
625                                         handle_sysrq(buf[i], tty);
626                                         sysrq_pressed = 0;
627                                         continue;
628                                 }
629                         }
630 #endif /* CONFIG_MAGIC_SYSRQ */
631                         tty_insert_flip_char(tty, buf[i], 0);
632                 }
633
634                 read_total += n;
635         }
636  throttled:
637         /* Wakeup write queue if necessary */
638         if (hp->do_wakeup) {
639                 hp->do_wakeup = 0;
640                 tty_wakeup(tty);
641         }
642  bail:
643         spin_unlock_irqrestore(&hp->lock, flags);
644
645         if (read_total)
646                 tty_flip_buffer_push(tty);
647         
648         return poll_mask;
649 }
650
651 #if defined(CONFIG_XMON) && defined(CONFIG_SMP)
652 extern cpumask_t cpus_in_xmon;
653 #else
654 static const cpumask_t cpus_in_xmon = CPU_MASK_NONE;
655 #endif
656
657 /*
658  * This kthread is either polling or interrupt driven.  This is determined by
659  * calling hvc_poll() who determines whether a console adapter support
660  * interrupts.
661  */
662 int khvcd(void *unused)
663 {
664         int poll_mask;
665         struct hvc_struct *hp;
666
667         __set_current_state(TASK_RUNNING);
668         do {
669                 poll_mask = 0;
670                 hvc_kicked = 0;
671                 try_to_freeze();
672                 wmb();
673                 if (cpus_empty(cpus_in_xmon)) {
674                         spin_lock(&hvc_structs_lock);
675                         list_for_each_entry(hp, &hvc_structs, next) {
676                                 poll_mask |= hvc_poll(hp);
677                         }
678                         spin_unlock(&hvc_structs_lock);
679                 } else
680                         poll_mask |= HVC_POLL_READ;
681                 if (hvc_kicked)
682                         continue;
683                 if (poll_mask & HVC_POLL_WRITE) {
684                         yield();
685                         continue;
686                 }
687                 set_current_state(TASK_INTERRUPTIBLE);
688                 if (!hvc_kicked) {
689                         if (poll_mask == 0)
690                                 schedule();
691                         else
692                                 msleep_interruptible(TIMEOUT);
693                 }
694                 __set_current_state(TASK_RUNNING);
695         } while (!kthread_should_stop());
696
697         return 0;
698 }
699
700 static const struct tty_operations hvc_ops = {
701         .open = hvc_open,
702         .close = hvc_close,
703         .write = hvc_write,
704         .hangup = hvc_hangup,
705         .unthrottle = hvc_unthrottle,
706         .write_room = hvc_write_room,
707         .chars_in_buffer = hvc_chars_in_buffer,
708 };
709
710 /* callback when the kboject ref count reaches zero. */
711 static void destroy_hvc_struct(struct kobject *kobj)
712 {
713         struct hvc_struct *hp = container_of(kobj, struct hvc_struct, kobj);
714         unsigned long flags;
715
716         spin_lock(&hvc_structs_lock);
717
718         spin_lock_irqsave(&hp->lock, flags);
719         list_del(&(hp->next));
720         spin_unlock_irqrestore(&hp->lock, flags);
721
722         spin_unlock(&hvc_structs_lock);
723
724         kfree(hp);
725 }
726
727 static struct kobj_type hvc_kobj_type = {
728         .release = destroy_hvc_struct,
729 };
730
731 struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
732                                         struct hv_ops *ops, int outbuf_size)
733 {
734         struct hvc_struct *hp;
735         int i;
736
737         hp = kmalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
738                         GFP_KERNEL);
739         if (!hp)
740                 return ERR_PTR(-ENOMEM);
741
742         memset(hp, 0x00, sizeof(*hp));
743
744         hp->vtermno = vtermno;
745         hp->irq = irq;
746         hp->ops = ops;
747         hp->outbuf_size = outbuf_size;
748         hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
749
750         kobject_init(&hp->kobj);
751         hp->kobj.ktype = &hvc_kobj_type;
752
753         spin_lock_init(&hp->lock);
754         spin_lock(&hvc_structs_lock);
755
756         /*
757          * find index to use:
758          * see if this vterm id matches one registered for console.
759          */
760         for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
761                 if (vtermnos[i] == hp->vtermno &&
762                     cons_ops[i] == hp->ops)
763                         break;
764
765         /* no matching slot, just use a counter */
766         if (i >= MAX_NR_HVC_CONSOLES)
767                 i = ++last_hvc;
768
769         hp->index = i;
770
771         list_add_tail(&(hp->next), &hvc_structs);
772         spin_unlock(&hvc_structs_lock);
773
774         return hp;
775 }
776 EXPORT_SYMBOL(hvc_alloc);
777
778 int __devexit hvc_remove(struct hvc_struct *hp)
779 {
780         unsigned long flags;
781         struct kobject *kobjp;
782         struct tty_struct *tty;
783
784         spin_lock_irqsave(&hp->lock, flags);
785         tty = hp->tty;
786         kobjp = &hp->kobj;
787
788         if (hp->index < MAX_NR_HVC_CONSOLES)
789                 vtermnos[hp->index] = -1;
790
791         /* Don't whack hp->irq because tty_hangup() will need to free the irq. */
792
793         spin_unlock_irqrestore(&hp->lock, flags);
794
795         /*
796          * We 'put' the instance that was grabbed when the kobject instance
797          * was intialized using kobject_init().  Let the last holder of this
798          * kobject cause it to be removed, which will probably be the tty_hangup
799          * below.
800          */
801         kobject_put(kobjp);
802
803         /*
804          * This function call will auto chain call hvc_hangup.  The tty should
805          * always be valid at this time unless a simultaneous tty close already
806          * cleaned up the hvc_struct.
807          */
808         if (tty)
809                 tty_hangup(tty);
810         return 0;
811 }
812 EXPORT_SYMBOL(hvc_remove);
813
814 /* Driver initialization.  Follow console initialization.  This is where the TTY
815  * interfaces start to become available. */
816 int __init hvc_init(void)
817 {
818         struct tty_driver *drv;
819
820         /* We need more than hvc_count adapters due to hotplug additions. */
821         drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
822         if (!drv)
823                 return -ENOMEM;
824
825         drv->owner = THIS_MODULE;
826         drv->driver_name = "hvc";
827         drv->name = "hvc";
828         drv->major = HVC_MAJOR;
829         drv->minor_start = HVC_MINOR;
830         drv->type = TTY_DRIVER_TYPE_SYSTEM;
831         drv->init_termios = tty_std_termios;
832         drv->flags = TTY_DRIVER_REAL_RAW;
833         tty_set_operations(drv, &hvc_ops);
834
835         /* Always start the kthread because there can be hotplug vty adapters
836          * added later. */
837         hvc_task = kthread_run(khvcd, NULL, "khvcd");
838         if (IS_ERR(hvc_task)) {
839                 panic("Couldn't create kthread for console.\n");
840                 put_tty_driver(drv);
841                 return -EIO;
842         }
843
844         if (tty_register_driver(drv))
845                 panic("Couldn't register hvc console driver\n");
846
847         mb();
848         hvc_driver = drv;
849         return 0;
850 }
851 module_init(hvc_init);
852
853 /* This isn't particularily necessary due to this being a console driver
854  * but it is nice to be thorough.
855  */
856 static void __exit hvc_exit(void)
857 {
858         kthread_stop(hvc_task);
859
860         tty_unregister_driver(hvc_driver);
861         /* return tty_struct instances allocated in hvc_init(). */
862         put_tty_driver(hvc_driver);
863         unregister_console(&hvc_con_driver);
864 }
865 module_exit(hvc_exit);