Merge git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc
[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
42 #include <asm/uaccess.h>
43
44 #include "hvc_console.h"
45
46 #define HVC_MAJOR       229
47 #define HVC_MINOR       0
48
49 #define TIMEOUT         (10)
50
51 /*
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.
54  */
55 #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
56
57 /*
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.
61  */
62 #define N_OUTBUF        16
63 #define N_INBUF         16
64
65 #define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
66
67 static struct tty_driver *hvc_driver;
68 static struct task_struct *hvc_task;
69
70 /* Picks up late kicks after list walk but before schedule() */
71 static int hvc_kicked;
72
73 #ifdef CONFIG_MAGIC_SYSRQ
74 static int sysrq_pressed;
75 #endif
76
77 struct hvc_struct {
78         spinlock_t lock;
79         int index;
80         struct tty_struct *tty;
81         unsigned int count;
82         int do_wakeup;
83         char *outbuf;
84         int outbuf_size;
85         int n_outbuf;
86         uint32_t vtermno;
87         struct hv_ops *ops;
88         int irq_requested;
89         int irq;
90         struct list_head next;
91         struct kobject kobj; /* ref count & hvc_struct lifetime */
92 };
93
94 /* dynamic list of hvc_struct instances */
95 static struct list_head hvc_structs = LIST_HEAD_INIT(hvc_structs);
96
97 /*
98  * Protect the list of hvc_struct instances from inserts and removals during
99  * list traversal.
100  */
101 static DEFINE_SPINLOCK(hvc_structs_lock);
102
103 /*
104  * This value is used to assign a tty->index value to a hvc_struct based
105  * upon order of exposure via hvc_probe(), when we can not match it to
106  * a console canidate registered with hvc_instantiate().
107  */
108 static int last_hvc = -1;
109
110 /*
111  * Do not call this function with either the hvc_strucst_lock or the hvc_struct
112  * lock held.  If successful, this function increments the kobject reference
113  * count against the target hvc_struct so it should be released when finished.
114  */
115 struct hvc_struct *hvc_get_by_index(int index)
116 {
117         struct hvc_struct *hp;
118         unsigned long flags;
119
120         spin_lock(&hvc_structs_lock);
121
122         list_for_each_entry(hp, &hvc_structs, next) {
123                 spin_lock_irqsave(&hp->lock, flags);
124                 if (hp->index == index) {
125                         kobject_get(&hp->kobj);
126                         spin_unlock_irqrestore(&hp->lock, flags);
127                         spin_unlock(&hvc_structs_lock);
128                         return hp;
129                 }
130                 spin_unlock_irqrestore(&hp->lock, flags);
131         }
132         hp = NULL;
133
134         spin_unlock(&hvc_structs_lock);
135         return hp;
136 }
137
138
139 /*
140  * Initial console vtermnos for console API usage prior to full console
141  * initialization.  Any vty adapter outside this range will not have usable
142  * console interfaces but can still be used as a tty device.  This has to be
143  * static because kmalloc will not work during early console init.
144  */
145 static struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
146 static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
147         {[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
148
149 /*
150  * Console APIs, NOT TTY.  These APIs are available immediately when
151  * hvc_console_setup() finds adapters.
152  */
153
154 void hvc_console_print(struct console *co, const char *b, unsigned count)
155 {
156         char c[N_OUTBUF] __ALIGNED__;
157         unsigned i = 0, n = 0;
158         int r, donecr = 0, index = co->index;
159
160         /* Console access attempt outside of acceptable console range. */
161         if (index >= MAX_NR_HVC_CONSOLES)
162                 return;
163
164         /* This console adapter was removed so it is not useable. */
165         if (vtermnos[index] < 0)
166                 return;
167
168         while (count > 0 || i > 0) {
169                 if (count > 0 && i < sizeof(c)) {
170                         if (b[n] == '\n' && !donecr) {
171                                 c[i++] = '\r';
172                                 donecr = 1;
173                         } else {
174                                 c[i++] = b[n++];
175                                 donecr = 0;
176                                 --count;
177                         }
178                 } else {
179                         r = cons_ops[index]->put_chars(vtermnos[index], c, i);
180                         if (r < 0) {
181                                 /* throw away chars on error */
182                                 i = 0;
183                         } else if (r > 0) {
184                                 i -= r;
185                                 if (i > 0)
186                                         memmove(c, c+r, i);
187                         }
188                 }
189         }
190 }
191
192 static struct tty_driver *hvc_console_device(struct console *c, int *index)
193 {
194         if (vtermnos[c->index] == -1)
195                 return NULL;
196
197         *index = c->index;
198         return hvc_driver;
199 }
200
201 static int __init hvc_console_setup(struct console *co, char *options)
202 {
203         if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
204                 return -ENODEV;
205
206         if (vtermnos[co->index] == -1)
207                 return -ENODEV;
208
209         return 0;
210 }
211
212 struct console hvc_con_driver = {
213         .name           = "hvc",
214         .write          = hvc_console_print,
215         .device         = hvc_console_device,
216         .setup          = hvc_console_setup,
217         .flags          = CON_PRINTBUFFER,
218         .index          = -1,
219 };
220
221 /*
222  * Early console initialization.  Preceeds driver initialization.
223  *
224  * (1) we are first, and the user specified another driver
225  * -- index will remain -1
226  * (2) we are first and the user specified no driver
227  * -- index will be set to 0, then we will fail setup.
228  * (3)  we are first and the user specified our driver
229  * -- index will be set to user specified driver, and we will fail
230  * (4) we are after driver, and this initcall will register us
231  * -- if the user didn't specify a driver then the console will match
232  *
233  * Note that for cases 2 and 3, we will match later when the io driver
234  * calls hvc_instantiate() and call register again.
235  */
236 static int __init hvc_console_init(void)
237 {
238         register_console(&hvc_con_driver);
239         return 0;
240 }
241 console_initcall(hvc_console_init);
242
243 /*
244  * hvc_instantiate() is an early console discovery method which locates
245  * consoles * prior to the vio subsystem discovering them.  Hotplugged
246  * vty adapters do NOT get an hvc_instantiate() callback since they
247  * appear after early console init.
248  */
249 int hvc_instantiate(uint32_t vtermno, int index, struct hv_ops *ops)
250 {
251         struct hvc_struct *hp;
252
253         if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
254                 return -1;
255
256         if (vtermnos[index] != -1)
257                 return -1;
258
259         /* make sure no no tty has been registerd in this index */
260         hp = hvc_get_by_index(index);
261         if (hp) {
262                 kobject_put(&hp->kobj);
263                 return -1;
264         }
265
266         vtermnos[index] = vtermno;
267         cons_ops[index] = ops;
268
269         /* reserve all indices upto and including this index */
270         if (last_hvc < index)
271                 last_hvc = index;
272
273         /* if this index is what the user requested, then register
274          * now (setup won't fail at this point).  It's ok to just
275          * call register again if previously .setup failed.
276          */
277         if (index == hvc_con_driver.index)
278                 register_console(&hvc_con_driver);
279
280         return 0;
281 }
282 EXPORT_SYMBOL(hvc_instantiate);
283
284 /* Wake the sleeping khvcd */
285 static void hvc_kick(void)
286 {
287         hvc_kicked = 1;
288         wake_up_process(hvc_task);
289 }
290
291 static int hvc_poll(struct hvc_struct *hp);
292
293 /*
294  * NOTE: This API isn't used if the console adapter doesn't support interrupts.
295  * In this case the console is poll driven.
296  */
297 static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance, struct pt_regs *regs)
298 {
299         /* if hvc_poll request a repoll, then kick the hvcd thread */
300         if (hvc_poll(dev_instance))
301                 hvc_kick();
302         return IRQ_HANDLED;
303 }
304
305 static void hvc_unthrottle(struct tty_struct *tty)
306 {
307         hvc_kick();
308 }
309
310 /*
311  * The TTY interface won't be used until after the vio layer has exposed the vty
312  * adapter to the kernel.
313  */
314 static int hvc_open(struct tty_struct *tty, struct file * filp)
315 {
316         struct hvc_struct *hp;
317         unsigned long flags;
318         int irq = NO_IRQ;
319         int rc = 0;
320         struct kobject *kobjp;
321
322         /* Auto increments kobject reference if found. */
323         if (!(hp = hvc_get_by_index(tty->index)))
324                 return -ENODEV;
325
326         spin_lock_irqsave(&hp->lock, flags);
327         /* Check and then increment for fast path open. */
328         if (hp->count++ > 0) {
329                 spin_unlock_irqrestore(&hp->lock, flags);
330                 hvc_kick();
331                 return 0;
332         } /* else count == 0 */
333
334         tty->driver_data = hp;
335         tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */
336
337         hp->tty = tty;
338         /* Save for request_irq outside of spin_lock. */
339         irq = hp->irq;
340         if (irq != NO_IRQ)
341                 hp->irq_requested = 1;
342
343         kobjp = &hp->kobj;
344
345         spin_unlock_irqrestore(&hp->lock, flags);
346         /* check error, fallback to non-irq */
347         if (irq != NO_IRQ)
348                 rc = request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED, "hvc_console", hp);
349
350         /*
351          * If the request_irq() fails and we return an error.  The tty layer
352          * will call hvc_close() after a failed open but we don't want to clean
353          * up there so we'll clean up here and clear out the previously set
354          * tty fields and return the kobject reference.
355          */
356         if (rc) {
357                 spin_lock_irqsave(&hp->lock, flags);
358                 hp->tty = NULL;
359                 hp->irq_requested = 0;
360                 spin_unlock_irqrestore(&hp->lock, flags);
361                 tty->driver_data = NULL;
362                 kobject_put(kobjp);
363                 printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
364         }
365         /* Force wakeup of the polling thread */
366         hvc_kick();
367
368         return rc;
369 }
370
371 static void hvc_close(struct tty_struct *tty, struct file * filp)
372 {
373         struct hvc_struct *hp;
374         struct kobject *kobjp;
375         int irq = NO_IRQ;
376         unsigned long flags;
377
378         if (tty_hung_up_p(filp))
379                 return;
380
381         /*
382          * No driver_data means that this close was issued after a failed
383          * hvc_open by the tty layer's release_dev() function and we can just
384          * exit cleanly because the kobject reference wasn't made.
385          */
386         if (!tty->driver_data)
387                 return;
388
389         hp = tty->driver_data;
390         spin_lock_irqsave(&hp->lock, flags);
391
392         kobjp = &hp->kobj;
393         if (--hp->count == 0) {
394                 if (hp->irq_requested)
395                         irq = hp->irq;
396                 hp->irq_requested = 0;
397
398                 /* We are done with the tty pointer now. */
399                 hp->tty = NULL;
400                 spin_unlock_irqrestore(&hp->lock, flags);
401
402                 /*
403                  * Chain calls chars_in_buffer() and returns immediately if
404                  * there is no buffered data otherwise sleeps on a wait queue
405                  * waking periodically to check chars_in_buffer().
406                  */
407                 tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
408
409                 if (irq != NO_IRQ)
410                         free_irq(irq, hp);
411
412         } else {
413                 if (hp->count < 0)
414                         printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
415                                 hp->vtermno, hp->count);
416                 spin_unlock_irqrestore(&hp->lock, flags);
417         }
418
419         kobject_put(kobjp);
420 }
421
422 static void hvc_hangup(struct tty_struct *tty)
423 {
424         struct hvc_struct *hp = tty->driver_data;
425         unsigned long flags;
426         int irq = NO_IRQ;
427         int temp_open_count;
428         struct kobject *kobjp;
429
430         if (!hp)
431                 return;
432
433         spin_lock_irqsave(&hp->lock, flags);
434
435         /*
436          * The N_TTY line discipline has problems such that in a close vs
437          * open->hangup case this can be called after the final close so prevent
438          * that from happening for now.
439          */
440         if (hp->count <= 0) {
441                 spin_unlock_irqrestore(&hp->lock, flags);
442                 return;
443         }
444
445         kobjp = &hp->kobj;
446         temp_open_count = hp->count;
447         hp->count = 0;
448         hp->n_outbuf = 0;
449         hp->tty = NULL;
450         if (hp->irq_requested)
451                 /* Saved for use outside of spin_lock. */
452                 irq = hp->irq;
453         hp->irq_requested = 0;
454         spin_unlock_irqrestore(&hp->lock, flags);
455         if (irq != NO_IRQ)
456                 free_irq(irq, hp);
457         while(temp_open_count) {
458                 --temp_open_count;
459                 kobject_put(kobjp);
460         }
461 }
462
463 /*
464  * Push buffered characters whether they were just recently buffered or waiting
465  * on a blocked hypervisor.  Call this function with hp->lock held.
466  */
467 static void hvc_push(struct hvc_struct *hp)
468 {
469         int n;
470
471         n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
472         if (n <= 0) {
473                 if (n == 0) {
474                         hp->do_wakeup = 1;
475                         return;
476                 }
477                 /* throw away output on error; this happens when
478                    there is no session connected to the vterm. */
479                 hp->n_outbuf = 0;
480         } else
481                 hp->n_outbuf -= n;
482         if (hp->n_outbuf > 0)
483                 memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
484         else
485                 hp->do_wakeup = 1;
486 }
487
488 static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
489 {
490         struct hvc_struct *hp = tty->driver_data;
491         unsigned long flags;
492         int rsize, written = 0;
493
494         /* This write was probably executed during a tty close. */
495         if (!hp)
496                 return -EPIPE;
497
498         if (hp->count <= 0)
499                 return -EIO;
500
501         spin_lock_irqsave(&hp->lock, flags);
502
503         /* Push pending writes */
504         if (hp->n_outbuf > 0)
505                 hvc_push(hp);
506
507         while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
508                 if (rsize > count)
509                         rsize = count;
510                 memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
511                 count -= rsize;
512                 buf += rsize;
513                 hp->n_outbuf += rsize;
514                 written += rsize;
515                 hvc_push(hp);
516         }
517         spin_unlock_irqrestore(&hp->lock, flags);
518
519         /*
520          * Racy, but harmless, kick thread if there is still pending data.
521          */
522         if (hp->n_outbuf)
523                 hvc_kick();
524
525         return written;
526 }
527
528 /*
529  * This is actually a contract between the driver and the tty layer outlining
530  * how much write room the driver can guarentee will be sent OR BUFFERED.  This
531  * driver MUST honor the return value.
532  */
533 static int hvc_write_room(struct tty_struct *tty)
534 {
535         struct hvc_struct *hp = tty->driver_data;
536
537         if (!hp)
538                 return -1;
539
540         return hp->outbuf_size - hp->n_outbuf;
541 }
542
543 static int hvc_chars_in_buffer(struct tty_struct *tty)
544 {
545         struct hvc_struct *hp = tty->driver_data;
546
547         if (!hp)
548                 return -1;
549         return hp->n_outbuf;
550 }
551
552 #define HVC_POLL_READ   0x00000001
553 #define HVC_POLL_WRITE  0x00000002
554
555 static int hvc_poll(struct hvc_struct *hp)
556 {
557         struct tty_struct *tty;
558         int i, n, poll_mask = 0;
559         char buf[N_INBUF] __ALIGNED__;
560         unsigned long flags;
561         int read_total = 0;
562
563         spin_lock_irqsave(&hp->lock, flags);
564
565         /* Push pending writes */
566         if (hp->n_outbuf > 0)
567                 hvc_push(hp);
568
569         /* Reschedule us if still some write pending */
570         if (hp->n_outbuf > 0)
571                 poll_mask |= HVC_POLL_WRITE;
572
573         /* No tty attached, just skip */
574         tty = hp->tty;
575         if (tty == NULL)
576                 goto bail;
577
578         /* Now check if we can get data (are we throttled ?) */
579         if (test_bit(TTY_THROTTLED, &tty->flags))
580                 goto throttled;
581
582         /* If we aren't interrupt driven and aren't throttled, we always
583          * request a reschedule
584          */
585         if (hp->irq == NO_IRQ)
586                 poll_mask |= HVC_POLL_READ;
587
588         /* Read data if any */
589         for (;;) {
590                 int count = tty_buffer_request_room(tty, N_INBUF);
591
592                 /* If flip is full, just reschedule a later read */
593                 if (count == 0) {
594                         poll_mask |= HVC_POLL_READ;
595                         break;
596                 }
597
598                 n = hp->ops->get_chars(hp->vtermno, buf, count);
599                 if (n <= 0) {
600                         /* Hangup the tty when disconnected from host */
601                         if (n == -EPIPE) {
602                                 spin_unlock_irqrestore(&hp->lock, flags);
603                                 tty_hangup(tty);
604                                 spin_lock_irqsave(&hp->lock, flags);
605                         } else if ( n == -EAGAIN ) {
606                                 /*
607                                  * Some back-ends can only ensure a certain min
608                                  * num of bytes read, which may be > 'count'.
609                                  * Let the tty clear the flip buff to make room.
610                                  */
611                                 poll_mask |= HVC_POLL_READ;
612                         }
613                         break;
614                 }
615                 for (i = 0; i < n; ++i) {
616 #ifdef CONFIG_MAGIC_SYSRQ
617                         if (hp->index == hvc_con_driver.index) {
618                                 /* Handle the SysRq Hack */
619                                 /* XXX should support a sequence */
620                                 if (buf[i] == '\x0f') { /* ^O */
621                                         sysrq_pressed = 1;
622                                         continue;
623                                 } else if (sysrq_pressed) {
624                                         handle_sysrq(buf[i], NULL, tty);
625                                         sysrq_pressed = 0;
626                                         continue;
627                                 }
628                         }
629 #endif /* CONFIG_MAGIC_SYSRQ */
630                         tty_insert_flip_char(tty, buf[i], 0);
631                 }
632
633                 read_total += n;
634         }
635  throttled:
636         /* Wakeup write queue if necessary */
637         if (hp->do_wakeup) {
638                 hp->do_wakeup = 0;
639                 tty_wakeup(tty);
640         }
641  bail:
642         spin_unlock_irqrestore(&hp->lock, flags);
643
644         if (read_total)
645                 tty_flip_buffer_push(tty);
646         
647         return poll_mask;
648 }
649
650 #if defined(CONFIG_XMON) && defined(CONFIG_SMP)
651 extern cpumask_t cpus_in_xmon;
652 #else
653 static const cpumask_t cpus_in_xmon = CPU_MASK_NONE;
654 #endif
655
656 /*
657  * This kthread is either polling or interrupt driven.  This is determined by
658  * calling hvc_poll() who determines whether a console adapter support
659  * interrupts.
660  */
661 int khvcd(void *unused)
662 {
663         int poll_mask;
664         struct hvc_struct *hp;
665
666         __set_current_state(TASK_RUNNING);
667         do {
668                 poll_mask = 0;
669                 hvc_kicked = 0;
670                 try_to_freeze();
671                 wmb();
672                 if (cpus_empty(cpus_in_xmon)) {
673                         spin_lock(&hvc_structs_lock);
674                         list_for_each_entry(hp, &hvc_structs, next) {
675                                 poll_mask |= hvc_poll(hp);
676                         }
677                         spin_unlock(&hvc_structs_lock);
678                 } else
679                         poll_mask |= HVC_POLL_READ;
680                 if (hvc_kicked)
681                         continue;
682                 if (poll_mask & HVC_POLL_WRITE) {
683                         yield();
684                         continue;
685                 }
686                 set_current_state(TASK_INTERRUPTIBLE);
687                 if (!hvc_kicked) {
688                         if (poll_mask == 0)
689                                 schedule();
690                         else
691                                 msleep_interruptible(TIMEOUT);
692                 }
693                 __set_current_state(TASK_RUNNING);
694         } while (!kthread_should_stop());
695
696         return 0;
697 }
698
699 static struct tty_operations hvc_ops = {
700         .open = hvc_open,
701         .close = hvc_close,
702         .write = hvc_write,
703         .hangup = hvc_hangup,
704         .unthrottle = hvc_unthrottle,
705         .write_room = hvc_write_room,
706         .chars_in_buffer = hvc_chars_in_buffer,
707 };
708
709 /* callback when the kboject ref count reaches zero. */
710 static void destroy_hvc_struct(struct kobject *kobj)
711 {
712         struct hvc_struct *hp = container_of(kobj, struct hvc_struct, kobj);
713         unsigned long flags;
714
715         spin_lock(&hvc_structs_lock);
716
717         spin_lock_irqsave(&hp->lock, flags);
718         list_del(&(hp->next));
719         spin_unlock_irqrestore(&hp->lock, flags);
720
721         spin_unlock(&hvc_structs_lock);
722
723         kfree(hp);
724 }
725
726 static struct kobj_type hvc_kobj_type = {
727         .release = destroy_hvc_struct,
728 };
729
730 struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
731                                         struct hv_ops *ops, int outbuf_size)
732 {
733         struct hvc_struct *hp;
734         int i;
735
736         hp = kmalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
737                         GFP_KERNEL);
738         if (!hp)
739                 return ERR_PTR(-ENOMEM);
740
741         memset(hp, 0x00, sizeof(*hp));
742
743         hp->vtermno = vtermno;
744         hp->irq = irq;
745         hp->ops = ops;
746         hp->outbuf_size = outbuf_size;
747         hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
748
749         kobject_init(&hp->kobj);
750         hp->kobj.ktype = &hvc_kobj_type;
751
752         spin_lock_init(&hp->lock);
753         spin_lock(&hvc_structs_lock);
754
755         /*
756          * find index to use:
757          * see if this vterm id matches one registered for console.
758          */
759         for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
760                 if (vtermnos[i] == hp->vtermno &&
761                     cons_ops[i] == hp->ops)
762                         break;
763
764         /* no matching slot, just use a counter */
765         if (i >= MAX_NR_HVC_CONSOLES)
766                 i = ++last_hvc;
767
768         hp->index = i;
769
770         list_add_tail(&(hp->next), &hvc_structs);
771         spin_unlock(&hvc_structs_lock);
772
773         return hp;
774 }
775 EXPORT_SYMBOL(hvc_alloc);
776
777 int __devexit hvc_remove(struct hvc_struct *hp)
778 {
779         unsigned long flags;
780         struct kobject *kobjp;
781         struct tty_struct *tty;
782
783         spin_lock_irqsave(&hp->lock, flags);
784         tty = hp->tty;
785         kobjp = &hp->kobj;
786
787         if (hp->index < MAX_NR_HVC_CONSOLES)
788                 vtermnos[hp->index] = -1;
789
790         /* Don't whack hp->irq because tty_hangup() will need to free the irq. */
791
792         spin_unlock_irqrestore(&hp->lock, flags);
793
794         /*
795          * We 'put' the instance that was grabbed when the kobject instance
796          * was intialized using kobject_init().  Let the last holder of this
797          * kobject cause it to be removed, which will probably be the tty_hangup
798          * below.
799          */
800         kobject_put(kobjp);
801
802         /*
803          * This function call will auto chain call hvc_hangup.  The tty should
804          * always be valid at this time unless a simultaneous tty close already
805          * cleaned up the hvc_struct.
806          */
807         if (tty)
808                 tty_hangup(tty);
809         return 0;
810 }
811 EXPORT_SYMBOL(hvc_remove);
812
813 /* Driver initialization.  Follow console initialization.  This is where the TTY
814  * interfaces start to become available. */
815 int __init hvc_init(void)
816 {
817         struct tty_driver *drv;
818
819         /* We need more than hvc_count adapters due to hotplug additions. */
820         drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
821         if (!drv)
822                 return -ENOMEM;
823
824         drv->owner = THIS_MODULE;
825         drv->driver_name = "hvc";
826         drv->name = "hvc";
827         drv->major = HVC_MAJOR;
828         drv->minor_start = HVC_MINOR;
829         drv->type = TTY_DRIVER_TYPE_SYSTEM;
830         drv->init_termios = tty_std_termios;
831         drv->flags = TTY_DRIVER_REAL_RAW;
832         tty_set_operations(drv, &hvc_ops);
833
834         /* Always start the kthread because there can be hotplug vty adapters
835          * added later. */
836         hvc_task = kthread_run(khvcd, NULL, "khvcd");
837         if (IS_ERR(hvc_task)) {
838                 panic("Couldn't create kthread for console.\n");
839                 put_tty_driver(drv);
840                 return -EIO;
841         }
842
843         if (tty_register_driver(drv))
844                 panic("Couldn't register hvc console driver\n");
845
846         mb();
847         hvc_driver = drv;
848         return 0;
849 }
850 module_init(hvc_init);
851
852 /* This isn't particularily necessary due to this being a console driver
853  * but it is nice to be thorough.
854  */
855 static void __exit hvc_exit(void)
856 {
857         kthread_stop(hvc_task);
858
859         tty_unregister_driver(hvc_driver);
860         /* return tty_struct instances allocated in hvc_init(). */
861         put_tty_driver(hvc_driver);
862         unregister_console(&hvc_con_driver);
863 }
864 module_exit(hvc_exit);