Root/drivers/char/apm-emulation.c

1/*
2 * bios-less APM driver for ARM Linux
3 * Jamey Hicks <jamey@crl.dec.com>
4 * adapted from the APM BIOS driver for Linux by Stephen Rothwell (sfr@linuxcare.com)
5 *
6 * APM 1.2 Reference:
7 * Intel Corporation, Microsoft Corporation. Advanced Power Management
8 * (APM) BIOS Interface Specification, Revision 1.2, February 1996.
9 *
10 * This document is available from Microsoft at:
11 * http://www.microsoft.com/whdc/archive/amp_12.mspx
12 */
13#include <linux/module.h>
14#include <linux/poll.h>
15#include <linux/slab.h>
16#include <linux/mutex.h>
17#include <linux/proc_fs.h>
18#include <linux/seq_file.h>
19#include <linux/miscdevice.h>
20#include <linux/apm_bios.h>
21#include <linux/capability.h>
22#include <linux/sched.h>
23#include <linux/suspend.h>
24#include <linux/apm-emulation.h>
25#include <linux/freezer.h>
26#include <linux/device.h>
27#include <linux/kernel.h>
28#include <linux/list.h>
29#include <linux/init.h>
30#include <linux/completion.h>
31#include <linux/kthread.h>
32#include <linux/delay.h>
33
34
35/*
36 * The apm_bios device is one of the misc char devices.
37 * This is its minor number.
38 */
39#define APM_MINOR_DEV 134
40
41/*
42 * One option can be changed at boot time as follows:
43 * apm=on/off enable/disable APM
44 */
45
46/*
47 * Maximum number of events stored
48 */
49#define APM_MAX_EVENTS 16
50
51struct apm_queue {
52    unsigned int event_head;
53    unsigned int event_tail;
54    apm_event_t events[APM_MAX_EVENTS];
55};
56
57/*
58 * thread states (for threads using a writable /dev/apm_bios fd):
59 *
60 * SUSPEND_NONE: nothing happening
61 * SUSPEND_PENDING: suspend event queued for thread and pending to be read
62 * SUSPEND_READ: suspend event read, pending acknowledgement
63 * SUSPEND_ACKED: acknowledgement received from thread (via ioctl),
64 * waiting for resume
65 * SUSPEND_ACKTO: acknowledgement timeout
66 * SUSPEND_DONE: thread had acked suspend and is now notified of
67 * resume
68 *
69 * SUSPEND_WAIT: this thread invoked suspend and is waiting for resume
70 *
71 * A thread migrates in one of three paths:
72 * NONE -1-> PENDING -2-> READ -3-> ACKED -4-> DONE -5-> NONE
73 * -6-> ACKTO -7-> NONE
74 * NONE -8-> WAIT -9-> NONE
75 *
76 * While in PENDING or READ, the thread is accounted for in the
77 * suspend_acks_pending counter.
78 *
79 * The transitions are invoked as follows:
80 * 1: suspend event is signalled from the core PM code
81 * 2: the suspend event is read from the fd by the userspace thread
82 * 3: userspace thread issues the APM_IOC_SUSPEND ioctl (as ack)
83 * 4: core PM code signals that we have resumed
84 * 5: APM_IOC_SUSPEND ioctl returns
85 *
86 * 6: the notifier invoked from the core PM code timed out waiting
87 * for all relevant threds to enter ACKED state and puts those
88 * that haven't into ACKTO
89 * 7: those threads issue APM_IOC_SUSPEND ioctl too late,
90 * get an error
91 *
92 * 8: userspace thread issues the APM_IOC_SUSPEND ioctl (to suspend),
93 * ioctl code invokes pm_suspend()
94 * 9: pm_suspend() returns indicating resume
95 */
96enum apm_suspend_state {
97    SUSPEND_NONE,
98    SUSPEND_PENDING,
99    SUSPEND_READ,
100    SUSPEND_ACKED,
101    SUSPEND_ACKTO,
102    SUSPEND_WAIT,
103    SUSPEND_DONE,
104};
105
106/*
107 * The per-file APM data
108 */
109struct apm_user {
110    struct list_head list;
111
112    unsigned int suser: 1;
113    unsigned int writer: 1;
114    unsigned int reader: 1;
115
116    int suspend_result;
117    enum apm_suspend_state suspend_state;
118
119    struct apm_queue queue;
120};
121
122/*
123 * Local variables
124 */
125static atomic_t suspend_acks_pending = ATOMIC_INIT(0);
126static atomic_t userspace_notification_inhibit = ATOMIC_INIT(0);
127static int apm_disabled;
128static struct task_struct *kapmd_tsk;
129
130static DECLARE_WAIT_QUEUE_HEAD(apm_waitqueue);
131static DECLARE_WAIT_QUEUE_HEAD(apm_suspend_waitqueue);
132
133/*
134 * This is a list of everyone who has opened /dev/apm_bios
135 */
136static DECLARE_RWSEM(user_list_lock);
137static LIST_HEAD(apm_user_list);
138
139/*
140 * kapmd info. kapmd provides us a process context to handle
141 * "APM" events within - specifically necessary if we're going
142 * to be suspending the system.
143 */
144static DECLARE_WAIT_QUEUE_HEAD(kapmd_wait);
145static DEFINE_SPINLOCK(kapmd_queue_lock);
146static struct apm_queue kapmd_queue;
147
148static DEFINE_MUTEX(state_lock);
149
150static const char driver_version[] = "1.13"; /* no spaces */
151
152
153
154/*
155 * Compatibility cruft until the IPAQ people move over to the new
156 * interface.
157 */
158static void __apm_get_power_status(struct apm_power_info *info)
159{
160}
161
162/*
163 * This allows machines to provide their own "apm get power status" function.
164 */
165void (*apm_get_power_status)(struct apm_power_info *) = __apm_get_power_status;
166EXPORT_SYMBOL(apm_get_power_status);
167
168
169/*
170 * APM event queue management.
171 */
172static inline int queue_empty(struct apm_queue *q)
173{
174    return q->event_head == q->event_tail;
175}
176
177static inline apm_event_t queue_get_event(struct apm_queue *q)
178{
179    q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
180    return q->events[q->event_tail];
181}
182
183static void queue_add_event(struct apm_queue *q, apm_event_t event)
184{
185    q->event_head = (q->event_head + 1) % APM_MAX_EVENTS;
186    if (q->event_head == q->event_tail) {
187        static int notified;
188
189        if (notified++ == 0)
190            printk(KERN_ERR "apm: an event queue overflowed\n");
191        q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
192    }
193    q->events[q->event_head] = event;
194}
195
196static void queue_event(apm_event_t event)
197{
198    struct apm_user *as;
199
200    down_read(&user_list_lock);
201    list_for_each_entry(as, &apm_user_list, list) {
202        if (as->reader)
203            queue_add_event(&as->queue, event);
204    }
205    up_read(&user_list_lock);
206    wake_up_interruptible(&apm_waitqueue);
207}
208
209static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
210{
211    struct apm_user *as = fp->private_data;
212    apm_event_t event;
213    int i = count, ret = 0;
214
215    if (count < sizeof(apm_event_t))
216        return -EINVAL;
217
218    if (queue_empty(&as->queue) && fp->f_flags & O_NONBLOCK)
219        return -EAGAIN;
220
221    wait_event_interruptible(apm_waitqueue, !queue_empty(&as->queue));
222
223    while ((i >= sizeof(event)) && !queue_empty(&as->queue)) {
224        event = queue_get_event(&as->queue);
225
226        ret = -EFAULT;
227        if (copy_to_user(buf, &event, sizeof(event)))
228            break;
229
230        mutex_lock(&state_lock);
231        if (as->suspend_state == SUSPEND_PENDING &&
232            (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND))
233            as->suspend_state = SUSPEND_READ;
234        mutex_unlock(&state_lock);
235
236        buf += sizeof(event);
237        i -= sizeof(event);
238    }
239
240    if (i < count)
241        ret = count - i;
242
243    return ret;
244}
245
246static unsigned int apm_poll(struct file *fp, poll_table * wait)
247{
248    struct apm_user *as = fp->private_data;
249
250    poll_wait(fp, &apm_waitqueue, wait);
251    return queue_empty(&as->queue) ? 0 : POLLIN | POLLRDNORM;
252}
253
254/*
255 * apm_ioctl - handle APM ioctl
256 *
257 * APM_IOC_SUSPEND
258 * This IOCTL is overloaded, and performs two functions. It is used to:
259 * - initiate a suspend
260 * - acknowledge a suspend read from /dev/apm_bios.
261 * Only when everyone who has opened /dev/apm_bios with write permission
262 * has acknowledge does the actual suspend happen.
263 */
264static long
265apm_ioctl(struct file *filp, u_int cmd, u_long arg)
266{
267    struct apm_user *as = filp->private_data;
268    int err = -EINVAL;
269
270    if (!as->suser || !as->writer)
271        return -EPERM;
272
273    switch (cmd) {
274    case APM_IOC_SUSPEND:
275        mutex_lock(&state_lock);
276
277        as->suspend_result = -EINTR;
278
279        switch (as->suspend_state) {
280        case SUSPEND_READ:
281            /*
282             * If we read a suspend command from /dev/apm_bios,
283             * then the corresponding APM_IOC_SUSPEND ioctl is
284             * interpreted as an acknowledge.
285             */
286            as->suspend_state = SUSPEND_ACKED;
287            atomic_dec(&suspend_acks_pending);
288            mutex_unlock(&state_lock);
289
290            /*
291             * suspend_acks_pending changed, the notifier needs to
292             * be woken up for this
293             */
294            wake_up(&apm_suspend_waitqueue);
295
296            /*
297             * Wait for the suspend/resume to complete. If there
298             * are pending acknowledges, we wait here for them.
299             * wait_event_freezable() is interruptible and pending
300             * signal can cause busy looping. We aren't doing
301             * anything critical, chill a bit on each iteration.
302             */
303            while (wait_event_freezable(apm_suspend_waitqueue,
304                    as->suspend_state != SUSPEND_ACKED))
305                msleep(10);
306            break;
307        case SUSPEND_ACKTO:
308            as->suspend_result = -ETIMEDOUT;
309            mutex_unlock(&state_lock);
310            break;
311        default:
312            as->suspend_state = SUSPEND_WAIT;
313            mutex_unlock(&state_lock);
314
315            /*
316             * Otherwise it is a request to suspend the system.
317             * Just invoke pm_suspend(), we'll handle it from
318             * there via the notifier.
319             */
320            as->suspend_result = pm_suspend(PM_SUSPEND_MEM);
321        }
322
323        mutex_lock(&state_lock);
324        err = as->suspend_result;
325        as->suspend_state = SUSPEND_NONE;
326        mutex_unlock(&state_lock);
327        break;
328    }
329
330    return err;
331}
332
333static int apm_release(struct inode * inode, struct file * filp)
334{
335    struct apm_user *as = filp->private_data;
336
337    filp->private_data = NULL;
338
339    down_write(&user_list_lock);
340    list_del(&as->list);
341    up_write(&user_list_lock);
342
343    /*
344     * We are now unhooked from the chain. As far as new
345     * events are concerned, we no longer exist.
346     */
347    mutex_lock(&state_lock);
348    if (as->suspend_state == SUSPEND_PENDING ||
349        as->suspend_state == SUSPEND_READ)
350        atomic_dec(&suspend_acks_pending);
351    mutex_unlock(&state_lock);
352
353    wake_up(&apm_suspend_waitqueue);
354
355    kfree(as);
356    return 0;
357}
358
359static int apm_open(struct inode * inode, struct file * filp)
360{
361    struct apm_user *as;
362
363    as = kzalloc(sizeof(*as), GFP_KERNEL);
364    if (as) {
365        /*
366         * XXX - this is a tiny bit broken, when we consider BSD
367         * process accounting. If the device is opened by root, we
368         * instantly flag that we used superuser privs. Who knows,
369         * we might close the device immediately without doing a
370         * privileged operation -- cevans
371         */
372        as->suser = capable(CAP_SYS_ADMIN);
373        as->writer = (filp->f_mode & FMODE_WRITE) == FMODE_WRITE;
374        as->reader = (filp->f_mode & FMODE_READ) == FMODE_READ;
375
376        down_write(&user_list_lock);
377        list_add(&as->list, &apm_user_list);
378        up_write(&user_list_lock);
379
380        filp->private_data = as;
381    }
382
383    return as ? 0 : -ENOMEM;
384}
385
386static const struct file_operations apm_bios_fops = {
387    .owner = THIS_MODULE,
388    .read = apm_read,
389    .poll = apm_poll,
390    .unlocked_ioctl = apm_ioctl,
391    .open = apm_open,
392    .release = apm_release,
393    .llseek = noop_llseek,
394};
395
396static struct miscdevice apm_device = {
397    .minor = APM_MINOR_DEV,
398    .name = "apm_bios",
399    .fops = &apm_bios_fops
400};
401
402
403#ifdef CONFIG_PROC_FS
404/*
405 * Arguments, with symbols from linux/apm_bios.h.
406 *
407 * 0) Linux driver version (this will change if format changes)
408 * 1) APM BIOS Version. Usually 1.0, 1.1 or 1.2.
409 * 2) APM flags from APM Installation Check (0x00):
410 * bit 0: APM_16_BIT_SUPPORT
411 * bit 1: APM_32_BIT_SUPPORT
412 * bit 2: APM_IDLE_SLOWS_CLOCK
413 * bit 3: APM_BIOS_DISABLED
414 * bit 4: APM_BIOS_DISENGAGED
415 * 3) AC line status
416 * 0x00: Off-line
417 * 0x01: On-line
418 * 0x02: On backup power (BIOS >= 1.1 only)
419 * 0xff: Unknown
420 * 4) Battery status
421 * 0x00: High
422 * 0x01: Low
423 * 0x02: Critical
424 * 0x03: Charging
425 * 0x04: Selected battery not present (BIOS >= 1.2 only)
426 * 0xff: Unknown
427 * 5) Battery flag
428 * bit 0: High
429 * bit 1: Low
430 * bit 2: Critical
431 * bit 3: Charging
432 * bit 7: No system battery
433 * 0xff: Unknown
434 * 6) Remaining battery life (percentage of charge):
435 * 0-100: valid
436 * -1: Unknown
437 * 7) Remaining battery life (time units):
438 * Number of remaining minutes or seconds
439 * -1: Unknown
440 * 8) min = minutes; sec = seconds
441 */
442static int proc_apm_show(struct seq_file *m, void *v)
443{
444    struct apm_power_info info;
445    char *units;
446
447    info.ac_line_status = 0xff;
448    info.battery_status = 0xff;
449    info.battery_flag = 0xff;
450    info.battery_life = -1;
451    info.time = -1;
452    info.units = -1;
453
454    if (apm_get_power_status)
455        apm_get_power_status(&info);
456
457    switch (info.units) {
458    default: units = "?"; break;
459    case 0: units = "min"; break;
460    case 1: units = "sec"; break;
461    }
462
463    seq_printf(m, "%s 1.2 0x%02x 0x%02x 0x%02x 0x%02x %d%% %d %s\n",
464             driver_version, APM_32_BIT_SUPPORT,
465             info.ac_line_status, info.battery_status,
466             info.battery_flag, info.battery_life,
467             info.time, units);
468
469    return 0;
470}
471
472static int proc_apm_open(struct inode *inode, struct file *file)
473{
474    return single_open(file, proc_apm_show, NULL);
475}
476
477static const struct file_operations apm_proc_fops = {
478    .owner = THIS_MODULE,
479    .open = proc_apm_open,
480    .read = seq_read,
481    .llseek = seq_lseek,
482    .release = single_release,
483};
484#endif
485
486static int kapmd(void *arg)
487{
488    do {
489        apm_event_t event;
490
491        wait_event_interruptible(kapmd_wait,
492                !queue_empty(&kapmd_queue) || kthread_should_stop());
493
494        if (kthread_should_stop())
495            break;
496
497        spin_lock_irq(&kapmd_queue_lock);
498        event = 0;
499        if (!queue_empty(&kapmd_queue))
500            event = queue_get_event(&kapmd_queue);
501        spin_unlock_irq(&kapmd_queue_lock);
502
503        switch (event) {
504        case 0:
505            break;
506
507        case APM_LOW_BATTERY:
508        case APM_POWER_STATUS_CHANGE:
509            queue_event(event);
510            break;
511
512        case APM_USER_SUSPEND:
513        case APM_SYS_SUSPEND:
514            pm_suspend(PM_SUSPEND_MEM);
515            break;
516
517        case APM_CRITICAL_SUSPEND:
518            atomic_inc(&userspace_notification_inhibit);
519            pm_suspend(PM_SUSPEND_MEM);
520            atomic_dec(&userspace_notification_inhibit);
521            break;
522        }
523    } while (1);
524
525    return 0;
526}
527
528static int apm_suspend_notifier(struct notifier_block *nb,
529                unsigned long event,
530                void *dummy)
531{
532    struct apm_user *as;
533    int err;
534
535    /* short-cut emergency suspends */
536    if (atomic_read(&userspace_notification_inhibit))
537        return NOTIFY_DONE;
538
539    switch (event) {
540    case PM_SUSPEND_PREPARE:
541        /*
542         * Queue an event to all "writer" users that we want
543         * to suspend and need their ack.
544         */
545        mutex_lock(&state_lock);
546        down_read(&user_list_lock);
547
548        list_for_each_entry(as, &apm_user_list, list) {
549            if (as->suspend_state != SUSPEND_WAIT && as->reader &&
550                as->writer && as->suser) {
551                as->suspend_state = SUSPEND_PENDING;
552                atomic_inc(&suspend_acks_pending);
553                queue_add_event(&as->queue, APM_USER_SUSPEND);
554            }
555        }
556
557        up_read(&user_list_lock);
558        mutex_unlock(&state_lock);
559        wake_up_interruptible(&apm_waitqueue);
560
561        /*
562         * Wait for the the suspend_acks_pending variable to drop to
563         * zero, meaning everybody acked the suspend event (or the
564         * process was killed.)
565         *
566         * If the app won't answer within a short while we assume it
567         * locked up and ignore it.
568         */
569        err = wait_event_interruptible_timeout(
570            apm_suspend_waitqueue,
571            atomic_read(&suspend_acks_pending) == 0,
572            5*HZ);
573
574        /* timed out */
575        if (err == 0) {
576            /*
577             * Move anybody who timed out to "ack timeout" state.
578             *
579             * We could time out and the userspace does the ACK
580             * right after we time out but before we enter the
581             * locked section here, but that's fine.
582             */
583            mutex_lock(&state_lock);
584            down_read(&user_list_lock);
585            list_for_each_entry(as, &apm_user_list, list) {
586                if (as->suspend_state == SUSPEND_PENDING ||
587                    as->suspend_state == SUSPEND_READ) {
588                    as->suspend_state = SUSPEND_ACKTO;
589                    atomic_dec(&suspend_acks_pending);
590                }
591            }
592            up_read(&user_list_lock);
593            mutex_unlock(&state_lock);
594        }
595
596        /* let suspend proceed */
597        if (err >= 0)
598            return NOTIFY_OK;
599
600        /* interrupted by signal */
601        return notifier_from_errno(err);
602
603    case PM_POST_SUSPEND:
604        /*
605         * Anyone on the APM queues will think we're still suspended.
606         * Send a message so everyone knows we're now awake again.
607         */
608        queue_event(APM_NORMAL_RESUME);
609
610        /*
611         * Finally, wake up anyone who is sleeping on the suspend.
612         */
613        mutex_lock(&state_lock);
614        down_read(&user_list_lock);
615        list_for_each_entry(as, &apm_user_list, list) {
616            if (as->suspend_state == SUSPEND_ACKED) {
617                /*
618                 * TODO: maybe grab error code, needs core
619                 * changes to push the error to the notifier
620                 * chain (could use the second parameter if
621                 * implemented)
622                 */
623                as->suspend_result = 0;
624                as->suspend_state = SUSPEND_DONE;
625            }
626        }
627        up_read(&user_list_lock);
628        mutex_unlock(&state_lock);
629
630        wake_up(&apm_suspend_waitqueue);
631        return NOTIFY_OK;
632
633    default:
634        return NOTIFY_DONE;
635    }
636}
637
638static struct notifier_block apm_notif_block = {
639    .notifier_call = apm_suspend_notifier,
640};
641
642static int __init apm_init(void)
643{
644    int ret;
645
646    if (apm_disabled) {
647        printk(KERN_NOTICE "apm: disabled on user request.\n");
648        return -ENODEV;
649    }
650
651    kapmd_tsk = kthread_create(kapmd, NULL, "kapmd");
652    if (IS_ERR(kapmd_tsk)) {
653        ret = PTR_ERR(kapmd_tsk);
654        kapmd_tsk = NULL;
655        goto out;
656    }
657    wake_up_process(kapmd_tsk);
658
659#ifdef CONFIG_PROC_FS
660    proc_create("apm", 0, NULL, &apm_proc_fops);
661#endif
662
663    ret = misc_register(&apm_device);
664    if (ret)
665        goto out_stop;
666
667    ret = register_pm_notifier(&apm_notif_block);
668    if (ret)
669        goto out_unregister;
670
671    return 0;
672
673 out_unregister:
674    misc_deregister(&apm_device);
675 out_stop:
676    remove_proc_entry("apm", NULL);
677    kthread_stop(kapmd_tsk);
678 out:
679    return ret;
680}
681
682static void __exit apm_exit(void)
683{
684    unregister_pm_notifier(&apm_notif_block);
685    misc_deregister(&apm_device);
686    remove_proc_entry("apm", NULL);
687
688    kthread_stop(kapmd_tsk);
689}
690
691module_init(apm_init);
692module_exit(apm_exit);
693
694MODULE_AUTHOR("Stephen Rothwell");
695MODULE_DESCRIPTION("Advanced Power Management");
696MODULE_LICENSE("GPL");
697
698#ifndef MODULE
699static int __init apm_setup(char *str)
700{
701    while ((str != NULL) && (*str != '\0')) {
702        if (strncmp(str, "off", 3) == 0)
703            apm_disabled = 1;
704        if (strncmp(str, "on", 2) == 0)
705            apm_disabled = 0;
706        str = strchr(str, ',');
707        if (str != NULL)
708            str += strspn(str, ", \t");
709    }
710    return 1;
711}
712
713__setup("apm=", apm_setup);
714#endif
715
716/**
717 * apm_queue_event - queue an APM event for kapmd
718 * @event: APM event
719 *
720 * Queue an APM event for kapmd to process and ultimately take the
721 * appropriate action. Only a subset of events are handled:
722 * %APM_LOW_BATTERY
723 * %APM_POWER_STATUS_CHANGE
724 * %APM_USER_SUSPEND
725 * %APM_SYS_SUSPEND
726 * %APM_CRITICAL_SUSPEND
727 */
728void apm_queue_event(apm_event_t event)
729{
730    unsigned long flags;
731
732    spin_lock_irqsave(&kapmd_queue_lock, flags);
733    queue_add_event(&kapmd_queue, event);
734    spin_unlock_irqrestore(&kapmd_queue_lock, flags);
735
736    wake_up_interruptible(&kapmd_wait);
737}
738EXPORT_SYMBOL(apm_queue_event);
739

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