GNU Linux-libre 5.19-rc6-gnu
[releases.git] / drivers / char / apm-emulation.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * bios-less APM driver for ARM Linux
4  *  Jamey Hicks <jamey@crl.dec.com>
5  *  adapted from the APM BIOS driver for Linux by Stephen Rothwell (sfr@linuxcare.com)
6  *
7  * APM 1.2 Reference:
8  *   Intel Corporation, Microsoft Corporation. Advanced Power Management
9  *   (APM) BIOS Interface Specification, Revision 1.2, February 1996.
10  *
11  * This document is available from Microsoft at:
12  *    http://www.microsoft.com/whdc/archive/amp_12.mspx
13  */
14 #include <linux/module.h>
15 #include <linux/poll.h>
16 #include <linux/slab.h>
17 #include <linux/mutex.h>
18 #include <linux/proc_fs.h>
19 #include <linux/seq_file.h>
20 #include <linux/miscdevice.h>
21 #include <linux/apm_bios.h>
22 #include <linux/capability.h>
23 #include <linux/sched.h>
24 #include <linux/suspend.h>
25 #include <linux/apm-emulation.h>
26 #include <linux/freezer.h>
27 #include <linux/device.h>
28 #include <linux/kernel.h>
29 #include <linux/list.h>
30 #include <linux/init.h>
31 #include <linux/completion.h>
32 #include <linux/kthread.h>
33 #include <linux/delay.h>
34
35 /*
36  * One option can be changed at boot time as follows:
37  *      apm=on/off                      enable/disable APM
38  */
39
40 /*
41  * Maximum number of events stored
42  */
43 #define APM_MAX_EVENTS          16
44
45 struct apm_queue {
46         unsigned int            event_head;
47         unsigned int            event_tail;
48         apm_event_t             events[APM_MAX_EVENTS];
49 };
50
51 /*
52  * thread states (for threads using a writable /dev/apm_bios fd):
53  *
54  * SUSPEND_NONE:        nothing happening
55  * SUSPEND_PENDING:     suspend event queued for thread and pending to be read
56  * SUSPEND_READ:        suspend event read, pending acknowledgement
57  * SUSPEND_ACKED:       acknowledgement received from thread (via ioctl),
58  *                      waiting for resume
59  * SUSPEND_ACKTO:       acknowledgement timeout
60  * SUSPEND_DONE:        thread had acked suspend and is now notified of
61  *                      resume
62  *
63  * SUSPEND_WAIT:        this thread invoked suspend and is waiting for resume
64  *
65  * A thread migrates in one of three paths:
66  *      NONE -1-> PENDING -2-> READ -3-> ACKED -4-> DONE -5-> NONE
67  *                                  -6-> ACKTO -7-> NONE
68  *      NONE -8-> WAIT -9-> NONE
69  *
70  * While in PENDING or READ, the thread is accounted for in the
71  * suspend_acks_pending counter.
72  *
73  * The transitions are invoked as follows:
74  *      1: suspend event is signalled from the core PM code
75  *      2: the suspend event is read from the fd by the userspace thread
76  *      3: userspace thread issues the APM_IOC_SUSPEND ioctl (as ack)
77  *      4: core PM code signals that we have resumed
78  *      5: APM_IOC_SUSPEND ioctl returns
79  *
80  *      6: the notifier invoked from the core PM code timed out waiting
81  *         for all relevant threds to enter ACKED state and puts those
82  *         that haven't into ACKTO
83  *      7: those threads issue APM_IOC_SUSPEND ioctl too late,
84  *         get an error
85  *
86  *      8: userspace thread issues the APM_IOC_SUSPEND ioctl (to suspend),
87  *         ioctl code invokes pm_suspend()
88  *      9: pm_suspend() returns indicating resume
89  */
90 enum apm_suspend_state {
91         SUSPEND_NONE,
92         SUSPEND_PENDING,
93         SUSPEND_READ,
94         SUSPEND_ACKED,
95         SUSPEND_ACKTO,
96         SUSPEND_WAIT,
97         SUSPEND_DONE,
98 };
99
100 /*
101  * The per-file APM data
102  */
103 struct apm_user {
104         struct list_head        list;
105
106         unsigned int            suser: 1;
107         unsigned int            writer: 1;
108         unsigned int            reader: 1;
109
110         int                     suspend_result;
111         enum apm_suspend_state  suspend_state;
112
113         struct apm_queue        queue;
114 };
115
116 /*
117  * Local variables
118  */
119 static atomic_t suspend_acks_pending = ATOMIC_INIT(0);
120 static atomic_t userspace_notification_inhibit = ATOMIC_INIT(0);
121 static int apm_disabled;
122 static struct task_struct *kapmd_tsk;
123
124 static DECLARE_WAIT_QUEUE_HEAD(apm_waitqueue);
125 static DECLARE_WAIT_QUEUE_HEAD(apm_suspend_waitqueue);
126
127 /*
128  * This is a list of everyone who has opened /dev/apm_bios
129  */
130 static DECLARE_RWSEM(user_list_lock);
131 static LIST_HEAD(apm_user_list);
132
133 /*
134  * kapmd info.  kapmd provides us a process context to handle
135  * "APM" events within - specifically necessary if we're going
136  * to be suspending the system.
137  */
138 static DECLARE_WAIT_QUEUE_HEAD(kapmd_wait);
139 static DEFINE_SPINLOCK(kapmd_queue_lock);
140 static struct apm_queue kapmd_queue;
141
142 static DEFINE_MUTEX(state_lock);
143
144 static const char driver_version[] = "1.13";    /* no spaces */
145
146
147
148 /*
149  * Compatibility cruft until the IPAQ people move over to the new
150  * interface.
151  */
152 static void __apm_get_power_status(struct apm_power_info *info)
153 {
154 }
155
156 /*
157  * This allows machines to provide their own "apm get power status" function.
158  */
159 void (*apm_get_power_status)(struct apm_power_info *) = __apm_get_power_status;
160 EXPORT_SYMBOL(apm_get_power_status);
161
162
163 /*
164  * APM event queue management.
165  */
166 static inline int queue_empty(struct apm_queue *q)
167 {
168         return q->event_head == q->event_tail;
169 }
170
171 static inline apm_event_t queue_get_event(struct apm_queue *q)
172 {
173         q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
174         return q->events[q->event_tail];
175 }
176
177 static void queue_add_event(struct apm_queue *q, apm_event_t event)
178 {
179         q->event_head = (q->event_head + 1) % APM_MAX_EVENTS;
180         if (q->event_head == q->event_tail) {
181                 static int notified;
182
183                 if (notified++ == 0)
184                     printk(KERN_ERR "apm: an event queue overflowed\n");
185                 q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
186         }
187         q->events[q->event_head] = event;
188 }
189
190 static void queue_event(apm_event_t event)
191 {
192         struct apm_user *as;
193
194         down_read(&user_list_lock);
195         list_for_each_entry(as, &apm_user_list, list) {
196                 if (as->reader)
197                         queue_add_event(&as->queue, event);
198         }
199         up_read(&user_list_lock);
200         wake_up_interruptible(&apm_waitqueue);
201 }
202
203 static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
204 {
205         struct apm_user *as = fp->private_data;
206         apm_event_t event;
207         int i = count, ret = 0;
208
209         if (count < sizeof(apm_event_t))
210                 return -EINVAL;
211
212         if (queue_empty(&as->queue) && fp->f_flags & O_NONBLOCK)
213                 return -EAGAIN;
214
215         wait_event_interruptible(apm_waitqueue, !queue_empty(&as->queue));
216
217         while ((i >= sizeof(event)) && !queue_empty(&as->queue)) {
218                 event = queue_get_event(&as->queue);
219
220                 ret = -EFAULT;
221                 if (copy_to_user(buf, &event, sizeof(event)))
222                         break;
223
224                 mutex_lock(&state_lock);
225                 if (as->suspend_state == SUSPEND_PENDING &&
226                     (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND))
227                         as->suspend_state = SUSPEND_READ;
228                 mutex_unlock(&state_lock);
229
230                 buf += sizeof(event);
231                 i -= sizeof(event);
232         }
233
234         if (i < count)
235                 ret = count - i;
236
237         return ret;
238 }
239
240 static __poll_t apm_poll(struct file *fp, poll_table * wait)
241 {
242         struct apm_user *as = fp->private_data;
243
244         poll_wait(fp, &apm_waitqueue, wait);
245         return queue_empty(&as->queue) ? 0 : EPOLLIN | EPOLLRDNORM;
246 }
247
248 /*
249  * apm_ioctl - handle APM ioctl
250  *
251  * APM_IOC_SUSPEND
252  *   This IOCTL is overloaded, and performs two functions.  It is used to:
253  *     - initiate a suspend
254  *     - acknowledge a suspend read from /dev/apm_bios.
255  *   Only when everyone who has opened /dev/apm_bios with write permission
256  *   has acknowledge does the actual suspend happen.
257  */
258 static long
259 apm_ioctl(struct file *filp, u_int cmd, u_long arg)
260 {
261         struct apm_user *as = filp->private_data;
262         int err = -EINVAL;
263
264         if (!as->suser || !as->writer)
265                 return -EPERM;
266
267         switch (cmd) {
268         case APM_IOC_SUSPEND:
269                 mutex_lock(&state_lock);
270
271                 as->suspend_result = -EINTR;
272
273                 switch (as->suspend_state) {
274                 case SUSPEND_READ:
275                         /*
276                          * If we read a suspend command from /dev/apm_bios,
277                          * then the corresponding APM_IOC_SUSPEND ioctl is
278                          * interpreted as an acknowledge.
279                          */
280                         as->suspend_state = SUSPEND_ACKED;
281                         atomic_dec(&suspend_acks_pending);
282                         mutex_unlock(&state_lock);
283
284                         /*
285                          * suspend_acks_pending changed, the notifier needs to
286                          * be woken up for this
287                          */
288                         wake_up(&apm_suspend_waitqueue);
289
290                         /*
291                          * Wait for the suspend/resume to complete.  If there
292                          * are pending acknowledges, we wait here for them.
293                          * wait_event_freezable() is interruptible and pending
294                          * signal can cause busy looping.  We aren't doing
295                          * anything critical, chill a bit on each iteration.
296                          */
297                         while (wait_event_freezable(apm_suspend_waitqueue,
298                                         as->suspend_state != SUSPEND_ACKED))
299                                 msleep(10);
300                         break;
301                 case SUSPEND_ACKTO:
302                         as->suspend_result = -ETIMEDOUT;
303                         mutex_unlock(&state_lock);
304                         break;
305                 default:
306                         as->suspend_state = SUSPEND_WAIT;
307                         mutex_unlock(&state_lock);
308
309                         /*
310                          * Otherwise it is a request to suspend the system.
311                          * Just invoke pm_suspend(), we'll handle it from
312                          * there via the notifier.
313                          */
314                         as->suspend_result = pm_suspend(PM_SUSPEND_MEM);
315                 }
316
317                 mutex_lock(&state_lock);
318                 err = as->suspend_result;
319                 as->suspend_state = SUSPEND_NONE;
320                 mutex_unlock(&state_lock);
321                 break;
322         }
323
324         return err;
325 }
326
327 static int apm_release(struct inode * inode, struct file * filp)
328 {
329         struct apm_user *as = filp->private_data;
330
331         filp->private_data = NULL;
332
333         down_write(&user_list_lock);
334         list_del(&as->list);
335         up_write(&user_list_lock);
336
337         /*
338          * We are now unhooked from the chain.  As far as new
339          * events are concerned, we no longer exist.
340          */
341         mutex_lock(&state_lock);
342         if (as->suspend_state == SUSPEND_PENDING ||
343             as->suspend_state == SUSPEND_READ)
344                 atomic_dec(&suspend_acks_pending);
345         mutex_unlock(&state_lock);
346
347         wake_up(&apm_suspend_waitqueue);
348
349         kfree(as);
350         return 0;
351 }
352
353 static int apm_open(struct inode * inode, struct file * filp)
354 {
355         struct apm_user *as;
356
357         as = kzalloc(sizeof(*as), GFP_KERNEL);
358         if (as) {
359                 /*
360                  * XXX - this is a tiny bit broken, when we consider BSD
361                  * process accounting. If the device is opened by root, we
362                  * instantly flag that we used superuser privs. Who knows,
363                  * we might close the device immediately without doing a
364                  * privileged operation -- cevans
365                  */
366                 as->suser = capable(CAP_SYS_ADMIN);
367                 as->writer = (filp->f_mode & FMODE_WRITE) == FMODE_WRITE;
368                 as->reader = (filp->f_mode & FMODE_READ) == FMODE_READ;
369
370                 down_write(&user_list_lock);
371                 list_add(&as->list, &apm_user_list);
372                 up_write(&user_list_lock);
373
374                 filp->private_data = as;
375         }
376
377         return as ? 0 : -ENOMEM;
378 }
379
380 static const struct file_operations apm_bios_fops = {
381         .owner          = THIS_MODULE,
382         .read           = apm_read,
383         .poll           = apm_poll,
384         .unlocked_ioctl = apm_ioctl,
385         .open           = apm_open,
386         .release        = apm_release,
387         .llseek         = noop_llseek,
388 };
389
390 static struct miscdevice apm_device = {
391         .minor          = APM_MINOR_DEV,
392         .name           = "apm_bios",
393         .fops           = &apm_bios_fops
394 };
395
396
397 #ifdef CONFIG_PROC_FS
398 /*
399  * Arguments, with symbols from linux/apm_bios.h.
400  *
401  *   0) Linux driver version (this will change if format changes)
402  *   1) APM BIOS Version.  Usually 1.0, 1.1 or 1.2.
403  *   2) APM flags from APM Installation Check (0x00):
404  *      bit 0: APM_16_BIT_SUPPORT
405  *      bit 1: APM_32_BIT_SUPPORT
406  *      bit 2: APM_IDLE_SLOWS_CLOCK
407  *      bit 3: APM_BIOS_DISABLED
408  *      bit 4: APM_BIOS_DISENGAGED
409  *   3) AC line status
410  *      0x00: Off-line
411  *      0x01: On-line
412  *      0x02: On backup power (BIOS >= 1.1 only)
413  *      0xff: Unknown
414  *   4) Battery status
415  *      0x00: High
416  *      0x01: Low
417  *      0x02: Critical
418  *      0x03: Charging
419  *      0x04: Selected battery not present (BIOS >= 1.2 only)
420  *      0xff: Unknown
421  *   5) Battery flag
422  *      bit 0: High
423  *      bit 1: Low
424  *      bit 2: Critical
425  *      bit 3: Charging
426  *      bit 7: No system battery
427  *      0xff: Unknown
428  *   6) Remaining battery life (percentage of charge):
429  *      0-100: valid
430  *      -1: Unknown
431  *   7) Remaining battery life (time units):
432  *      Number of remaining minutes or seconds
433  *      -1: Unknown
434  *   8) min = minutes; sec = seconds
435  */
436 static int proc_apm_show(struct seq_file *m, void *v)
437 {
438         struct apm_power_info info;
439         char *units;
440
441         info.ac_line_status = 0xff;
442         info.battery_status = 0xff;
443         info.battery_flag   = 0xff;
444         info.battery_life   = -1;
445         info.time           = -1;
446         info.units          = -1;
447
448         if (apm_get_power_status)
449                 apm_get_power_status(&info);
450
451         switch (info.units) {
452         default:        units = "?";    break;
453         case 0:         units = "min";  break;
454         case 1:         units = "sec";  break;
455         }
456
457         seq_printf(m, "%s 1.2 0x%02x 0x%02x 0x%02x 0x%02x %d%% %d %s\n",
458                      driver_version, APM_32_BIT_SUPPORT,
459                      info.ac_line_status, info.battery_status,
460                      info.battery_flag, info.battery_life,
461                      info.time, units);
462
463         return 0;
464 }
465 #endif
466
467 static int kapmd(void *arg)
468 {
469         do {
470                 apm_event_t event;
471
472                 wait_event_interruptible(kapmd_wait,
473                                 !queue_empty(&kapmd_queue) || kthread_should_stop());
474
475                 if (kthread_should_stop())
476                         break;
477
478                 spin_lock_irq(&kapmd_queue_lock);
479                 event = 0;
480                 if (!queue_empty(&kapmd_queue))
481                         event = queue_get_event(&kapmd_queue);
482                 spin_unlock_irq(&kapmd_queue_lock);
483
484                 switch (event) {
485                 case 0:
486                         break;
487
488                 case APM_LOW_BATTERY:
489                 case APM_POWER_STATUS_CHANGE:
490                         queue_event(event);
491                         break;
492
493                 case APM_USER_SUSPEND:
494                 case APM_SYS_SUSPEND:
495                         pm_suspend(PM_SUSPEND_MEM);
496                         break;
497
498                 case APM_CRITICAL_SUSPEND:
499                         atomic_inc(&userspace_notification_inhibit);
500                         pm_suspend(PM_SUSPEND_MEM);
501                         atomic_dec(&userspace_notification_inhibit);
502                         break;
503                 }
504         } while (1);
505
506         return 0;
507 }
508
509 static int apm_suspend_notifier(struct notifier_block *nb,
510                                 unsigned long event,
511                                 void *dummy)
512 {
513         struct apm_user *as;
514         int err;
515         unsigned long apm_event;
516
517         /* short-cut emergency suspends */
518         if (atomic_read(&userspace_notification_inhibit))
519                 return NOTIFY_DONE;
520
521         switch (event) {
522         case PM_SUSPEND_PREPARE:
523         case PM_HIBERNATION_PREPARE:
524                 apm_event = (event == PM_SUSPEND_PREPARE) ?
525                         APM_USER_SUSPEND : APM_USER_HIBERNATION;
526                 /*
527                  * Queue an event to all "writer" users that we want
528                  * to suspend and need their ack.
529                  */
530                 mutex_lock(&state_lock);
531                 down_read(&user_list_lock);
532
533                 list_for_each_entry(as, &apm_user_list, list) {
534                         if (as->suspend_state != SUSPEND_WAIT && as->reader &&
535                             as->writer && as->suser) {
536                                 as->suspend_state = SUSPEND_PENDING;
537                                 atomic_inc(&suspend_acks_pending);
538                                 queue_add_event(&as->queue, apm_event);
539                         }
540                 }
541
542                 up_read(&user_list_lock);
543                 mutex_unlock(&state_lock);
544                 wake_up_interruptible(&apm_waitqueue);
545
546                 /*
547                  * Wait for the the suspend_acks_pending variable to drop to
548                  * zero, meaning everybody acked the suspend event (or the
549                  * process was killed.)
550                  *
551                  * If the app won't answer within a short while we assume it
552                  * locked up and ignore it.
553                  */
554                 err = wait_event_interruptible_timeout(
555                         apm_suspend_waitqueue,
556                         atomic_read(&suspend_acks_pending) == 0,
557                         5*HZ);
558
559                 /* timed out */
560                 if (err == 0) {
561                         /*
562                          * Move anybody who timed out to "ack timeout" state.
563                          *
564                          * We could time out and the userspace does the ACK
565                          * right after we time out but before we enter the
566                          * locked section here, but that's fine.
567                          */
568                         mutex_lock(&state_lock);
569                         down_read(&user_list_lock);
570                         list_for_each_entry(as, &apm_user_list, list) {
571                                 if (as->suspend_state == SUSPEND_PENDING ||
572                                     as->suspend_state == SUSPEND_READ) {
573                                         as->suspend_state = SUSPEND_ACKTO;
574                                         atomic_dec(&suspend_acks_pending);
575                                 }
576                         }
577                         up_read(&user_list_lock);
578                         mutex_unlock(&state_lock);
579                 }
580
581                 /* let suspend proceed */
582                 if (err >= 0)
583                         return NOTIFY_OK;
584
585                 /* interrupted by signal */
586                 return notifier_from_errno(err);
587
588         case PM_POST_SUSPEND:
589         case PM_POST_HIBERNATION:
590                 apm_event = (event == PM_POST_SUSPEND) ?
591                         APM_NORMAL_RESUME : APM_HIBERNATION_RESUME;
592                 /*
593                  * Anyone on the APM queues will think we're still suspended.
594                  * Send a message so everyone knows we're now awake again.
595                  */
596                 queue_event(apm_event);
597
598                 /*
599                  * Finally, wake up anyone who is sleeping on the suspend.
600                  */
601                 mutex_lock(&state_lock);
602                 down_read(&user_list_lock);
603                 list_for_each_entry(as, &apm_user_list, list) {
604                         if (as->suspend_state == SUSPEND_ACKED) {
605                                 /*
606                                  * TODO: maybe grab error code, needs core
607                                  * changes to push the error to the notifier
608                                  * chain (could use the second parameter if
609                                  * implemented)
610                                  */
611                                 as->suspend_result = 0;
612                                 as->suspend_state = SUSPEND_DONE;
613                         }
614                 }
615                 up_read(&user_list_lock);
616                 mutex_unlock(&state_lock);
617
618                 wake_up(&apm_suspend_waitqueue);
619                 return NOTIFY_OK;
620
621         default:
622                 return NOTIFY_DONE;
623         }
624 }
625
626 static struct notifier_block apm_notif_block = {
627         .notifier_call = apm_suspend_notifier,
628 };
629
630 static int __init apm_init(void)
631 {
632         int ret;
633
634         if (apm_disabled) {
635                 printk(KERN_NOTICE "apm: disabled on user request.\n");
636                 return -ENODEV;
637         }
638
639         kapmd_tsk = kthread_create(kapmd, NULL, "kapmd");
640         if (IS_ERR(kapmd_tsk)) {
641                 ret = PTR_ERR(kapmd_tsk);
642                 kapmd_tsk = NULL;
643                 goto out;
644         }
645         wake_up_process(kapmd_tsk);
646
647 #ifdef CONFIG_PROC_FS
648         proc_create_single("apm", 0, NULL, proc_apm_show);
649 #endif
650
651         ret = misc_register(&apm_device);
652         if (ret)
653                 goto out_stop;
654
655         ret = register_pm_notifier(&apm_notif_block);
656         if (ret)
657                 goto out_unregister;
658
659         return 0;
660
661  out_unregister:
662         misc_deregister(&apm_device);
663  out_stop:
664         remove_proc_entry("apm", NULL);
665         kthread_stop(kapmd_tsk);
666  out:
667         return ret;
668 }
669
670 static void __exit apm_exit(void)
671 {
672         unregister_pm_notifier(&apm_notif_block);
673         misc_deregister(&apm_device);
674         remove_proc_entry("apm", NULL);
675
676         kthread_stop(kapmd_tsk);
677 }
678
679 module_init(apm_init);
680 module_exit(apm_exit);
681
682 MODULE_AUTHOR("Stephen Rothwell");
683 MODULE_DESCRIPTION("Advanced Power Management");
684 MODULE_LICENSE("GPL");
685
686 #ifndef MODULE
687 static int __init apm_setup(char *str)
688 {
689         while ((str != NULL) && (*str != '\0')) {
690                 if (strncmp(str, "off", 3) == 0)
691                         apm_disabled = 1;
692                 if (strncmp(str, "on", 2) == 0)
693                         apm_disabled = 0;
694                 str = strchr(str, ',');
695                 if (str != NULL)
696                         str += strspn(str, ", \t");
697         }
698         return 1;
699 }
700
701 __setup("apm=", apm_setup);
702 #endif
703
704 /**
705  * apm_queue_event - queue an APM event for kapmd
706  * @event: APM event
707  *
708  * Queue an APM event for kapmd to process and ultimately take the
709  * appropriate action.  Only a subset of events are handled:
710  *   %APM_LOW_BATTERY
711  *   %APM_POWER_STATUS_CHANGE
712  *   %APM_USER_SUSPEND
713  *   %APM_SYS_SUSPEND
714  *   %APM_CRITICAL_SUSPEND
715  */
716 void apm_queue_event(apm_event_t event)
717 {
718         unsigned long flags;
719
720         spin_lock_irqsave(&kapmd_queue_lock, flags);
721         queue_add_event(&kapmd_queue, event);
722         spin_unlock_irqrestore(&kapmd_queue_lock, flags);
723
724         wake_up_interruptible(&kapmd_wait);
725 }
726 EXPORT_SYMBOL(apm_queue_event);