apm-emulation.c

Go to the documentation of this file.

/*
 * bios-less APM driver for ARM Linux
 *  Jamey Hicks <[email protected]>
 *  adapted from the APM BIOS driver for Linux by Stephen Rothwell ([email protected])
 *
 * APM 1.2 Reference:
 *   Intel Corporation, Microsoft Corporation. Advanced Power Management
 *   (APM) BIOS Interface Specification, Revision 1.2, February 1996.
 *
 * This document is available from Microsoft at:
 *    http://www.microsoft.com/whdc/archive/amp_12.mspx
 */
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/miscdevice.h>
#include <linux/apm_bios.h>
#include <linux/capability.h>
#include <linux/sched.h>
#include <linux/suspend.h>
#include <linux/apm-emulation.h>
#include <linux/freezer.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/kthread.h>
#include <linux/delay.h>


/*
 * The apm_bios device is one of the misc char devices.
 * This is its minor number.
 */
#define APM_MINOR_DEV   134

/*
 * One option can be changed at boot time as follows:
 *  apm=on/off          enable/disable APM
 */

/*
 * Maximum number of events stored
 */
#define APM_MAX_EVENTS      16

struct apm_queue {
    unsigned int        event_head;
    unsigned int        event_tail;
    apm_event_t     events[APM_MAX_EVENTS];
};

/*
 * thread states (for threads using a writable /dev/apm_bios fd):
 *
 * SUSPEND_NONE:    nothing happening
 * SUSPEND_PENDING: suspend event queued for thread and pending to be read
 * SUSPEND_READ:    suspend event read, pending acknowledgement
 * SUSPEND_ACKED:   acknowledgement received from thread (via ioctl),
 *          waiting for resume
 * SUSPEND_ACKTO:   acknowledgement timeout
 * SUSPEND_DONE:    thread had acked suspend and is now notified of
 *          resume
 *
 * SUSPEND_WAIT:    this thread invoked suspend and is waiting for resume
 *
 * A thread migrates in one of three paths:
 *  NONE -1-> PENDING -2-> READ -3-> ACKED -4-> DONE -5-> NONE
 *                  -6-> ACKTO -7-> NONE
 *  NONE -8-> WAIT -9-> NONE
 *
 * While in PENDING or READ, the thread is accounted for in the
 * suspend_acks_pending counter.
 *
 * The transitions are invoked as follows:
 *  1: suspend event is signalled from the core PM code
 *  2: the suspend event is read from the fd by the userspace thread
 *  3: userspace thread issues the APM_IOC_SUSPEND ioctl (as ack)
 *  4: core PM code signals that we have resumed
 *  5: APM_IOC_SUSPEND ioctl returns
 *
 *  6: the notifier invoked from the core PM code timed out waiting
 *     for all relevant threds to enter ACKED state and puts those
 *     that haven't into ACKTO
 *  7: those threads issue APM_IOC_SUSPEND ioctl too late,
 *     get an error
 *
 *  8: userspace thread issues the APM_IOC_SUSPEND ioctl (to suspend),
 *     ioctl code invokes pm_suspend()
 *  9: pm_suspend() returns indicating resume
 */
enum apm_suspend_state {
    SUSPEND_NONE,
    SUSPEND_PENDING,
    SUSPEND_READ,
    SUSPEND_ACKED,
    SUSPEND_ACKTO,
    SUSPEND_WAIT,
    SUSPEND_DONE,
};

/*
 * The per-file APM data
 */
struct apm_user {
    struct list_head    list;

    unsigned int        suser: 1;
    unsigned int        writer: 1;
    unsigned int        reader: 1;

    int         suspend_result;
    enum apm_suspend_state  suspend_state;

    struct apm_queue    queue;
};

/*
 * Local variables
 */
static atomic_t suspend_acks_pending = ATOMIC_INIT(0);
static atomic_t userspace_notification_inhibit = ATOMIC_INIT(0);
static int apm_disabled;
static struct task_struct *kapmd_tsk;

static DECLARE_WAIT_QUEUE_HEAD(apm_waitqueue);
static DECLARE_WAIT_QUEUE_HEAD(apm_suspend_waitqueue);

/*
 * This is a list of everyone who has opened /dev/apm_bios
 */
static DECLARE_RWSEM(user_list_lock);
static LIST_HEAD(apm_user_list);

/*
 * kapmd info.  kapmd provides us a process context to handle
 * "APM" events within - specifically necessary if we're going
 * to be suspending the system.
 */
static DECLARE_WAIT_QUEUE_HEAD(kapmd_wait);
static DEFINE_SPINLOCK(kapmd_queue_lock);
static struct apm_queue kapmd_queue;

static DEFINE_MUTEX(state_lock);

static const char driver_version[] = "1.13";    /* no spaces */



/*
 * Compatibility cruft until the IPAQ people move over to the new
 * interface.
 */
static void __apm_get_power_status(struct apm_power_info *info)
{
}

/*
 * This allows machines to provide their own "apm get power status" function.
 */
void (*apm_get_power_status)(struct apm_power_info *) = __apm_get_power_status;
EXPORT_SYMBOL(apm_get_power_status);


/*
 * APM event queue management.
 */
static inline int queue_empty(struct apm_queue *q)
{
    return q->event_head == q->event_tail;
}

static inline apm_event_t queue_get_event(struct apm_queue *q)
{
    q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
    return q->events[q->event_tail];
}

static void queue_add_event(struct apm_queue *q, apm_event_t event)
{
    q->event_head = (q->event_head + 1) % APM_MAX_EVENTS;
    if (q->event_head == q->event_tail) {
        static int notified;

        if (notified++ == 0)
            printk(KERN_ERR "apm: an event queue overflowed\n");
        q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
    }
    q->events[q->event_head] = event;
}

static void queue_event(apm_event_t event)
{
    struct apm_user *as;

    down_read(&user_list_lock);
    list_for_each_entry(as, &apm_user_list, list) {
        if (as->reader)
            queue_add_event(&as->queue, event);
    }
    up_read(&user_list_lock);
    wake_up_interruptible(&apm_waitqueue);
}

static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
{
    struct apm_user *as = fp->private_data;
    apm_event_t event;
    int i = count, ret = 0;

    if (count < sizeof(apm_event_t))
        return -EINVAL;

    if (queue_empty(&as->queue) && fp->f_flags & O_NONBLOCK)
        return -EAGAIN;

    wait_event_interruptible(apm_waitqueue, !queue_empty(&as->queue));

    while ((i >= sizeof(event)) && !queue_empty(&as->queue)) {
        event = queue_get_event(&as->queue);

        ret = -EFAULT;
        if (copy_to_user(buf, &event, sizeof(event)))
            break;

        mutex_lock(&state_lock);
        if (as->suspend_state == SUSPEND_PENDING &&
            (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND))
            as->suspend_state = SUSPEND_READ;
        mutex_unlock(&state_lock);

        buf += sizeof(event);
        i -= sizeof(event);
    }

    if (i < count)
        ret = count - i;

    return ret;
}

static unsigned int apm_poll(struct file *fp, poll_table * wait)
{
    struct apm_user *as = fp->private_data;

    poll_wait(fp, &apm_waitqueue, wait);
    return queue_empty(&as->queue) ? 0 : POLLIN | POLLRDNORM;
}

/*
 * apm_ioctl - handle APM ioctl
 *
 * APM_IOC_SUSPEND
 *   This IOCTL is overloaded, and performs two functions.  It is used to:
 *     - initiate a suspend
 *     - acknowledge a suspend read from /dev/apm_bios.
 *   Only when everyone who has opened /dev/apm_bios with write permission
 *   has acknowledge does the actual suspend happen.
 */
static long
apm_ioctl(struct file *filp, u_int cmd, u_long arg)
{
    struct apm_user *as = filp->private_data;
    int err = -EINVAL;

    if (!as->suser || !as->writer)
        return -EPERM;

    switch (cmd) {
    case APM_IOC_SUSPEND:
        mutex_lock(&state_lock);

        as->suspend_result = -EINTR;

        switch (as->suspend_state) {
        case SUSPEND_READ:
            /*
             * If we read a suspend command from /dev/apm_bios,
             * then the corresponding APM_IOC_SUSPEND ioctl is
             * interpreted as an acknowledge.
             */
            as->suspend_state = SUSPEND_ACKED;
            atomic_dec(&suspend_acks_pending);
            mutex_unlock(&state_lock);

            /*
             * suspend_acks_pending changed, the notifier needs to
             * be woken up for this
             */
            wake_up(&apm_suspend_waitqueue);

            /*
             * Wait for the suspend/resume to complete.  If there
             * are pending acknowledges, we wait here for them.
             * wait_event_freezable() is interruptible and pending
             * signal can cause busy looping.  We aren't doing
             * anything critical, chill a bit on each iteration.
             */
            while (wait_event_freezable(apm_suspend_waitqueue,
                    as->suspend_state != SUSPEND_ACKED))
                msleep(10);
            break;
        case SUSPEND_ACKTO:
            as->suspend_result = -ETIMEDOUT;
            mutex_unlock(&state_lock);
            break;
        default:
            as->suspend_state = SUSPEND_WAIT;
            mutex_unlock(&state_lock);

            /*
             * Otherwise it is a request to suspend the system.
             * Just invoke pm_suspend(), we'll handle it from
             * there via the notifier.
             */
            as->suspend_result = pm_suspend(PM_SUSPEND_MEM);
        }

        mutex_lock(&state_lock);
        err = as->suspend_result;
        as->suspend_state = SUSPEND_NONE;
        mutex_unlock(&state_lock);
        break;
    }

    return err;
}

static int apm_release(struct inode * inode, struct file * filp)
{
    struct apm_user *as = filp->private_data;

    filp->private_data = NULL;

    down_write(&user_list_lock);
    list_del(&as->list);
    up_write(&user_list_lock);

    /*
     * We are now unhooked from the chain.  As far as new
     * events are concerned, we no longer exist.
     */
    mutex_lock(&state_lock);
    if (as->suspend_state == SUSPEND_PENDING ||
        as->suspend_state == SUSPEND_READ)
        atomic_dec(&suspend_acks_pending);
    mutex_unlock(&state_lock);

    wake_up(&apm_suspend_waitqueue);

    kfree(as);
    return 0;
}

static int apm_open(struct inode * inode, struct file * filp)
{
    struct apm_user *as;

    as = kzalloc(sizeof(*as), GFP_KERNEL);
    if (as) {
        /*
         * XXX - this is a tiny bit broken, when we consider BSD
         * process accounting. If the device is opened by root, we
         * instantly flag that we used superuser privs. Who knows,
         * we might close the device immediately without doing a
         * privileged operation -- cevans
         */
        as->suser = capable(CAP_SYS_ADMIN);
        as->writer = (filp->f_mode & FMODE_WRITE) == FMODE_WRITE;
        as->reader = (filp->f_mode & FMODE_READ) == FMODE_READ;

        down_write(&user_list_lock);
        list_add(&as->list, &apm_user_list);
        up_write(&user_list_lock);

        filp->private_data = as;
    }

    return as ? 0 : -ENOMEM;
}

static const struct file_operations apm_bios_fops = {
    .owner      = THIS_MODULE,
    .read       = apm_read,
    .poll       = apm_poll,
    .unlocked_ioctl = apm_ioctl,
    .open       = apm_open,
    .release    = apm_release,
    .llseek     = noop_llseek,
};

static struct miscdevice apm_device = {
    .minor      = APM_MINOR_DEV,
    .name       = "apm_bios",
    .fops       = &apm_bios_fops
};


#ifdef CONFIG_PROC_FS
/*
 * Arguments, with symbols from linux/apm_bios.h.
 *
 *   0) Linux driver version (this will change if format changes)
 *   1) APM BIOS Version.  Usually 1.0, 1.1 or 1.2.
 *   2) APM flags from APM Installation Check (0x00):
 *  bit 0: APM_16_BIT_SUPPORT
 *  bit 1: APM_32_BIT_SUPPORT
 *  bit 2: APM_IDLE_SLOWS_CLOCK
 *  bit 3: APM_BIOS_DISABLED
 *  bit 4: APM_BIOS_DISENGAGED
 *   3) AC line status
 *  0x00: Off-line
 *  0x01: On-line
 *  0x02: On backup power (BIOS >= 1.1 only)
 *  0xff: Unknown
 *   4) Battery status
 *  0x00: High
 *  0x01: Low
 *  0x02: Critical
 *  0x03: Charging
 *  0x04: Selected battery not present (BIOS >= 1.2 only)
 *  0xff: Unknown
 *   5) Battery flag
 *  bit 0: High
 *  bit 1: Low
 *  bit 2: Critical
 *  bit 3: Charging
 *  bit 7: No system battery
 *  0xff: Unknown
 *   6) Remaining battery life (percentage of charge):
 *  0-100: valid
 *  -1: Unknown
 *   7) Remaining battery life (time units):
 *  Number of remaining minutes or seconds
 *  -1: Unknown
 *   8) min = minutes; sec = seconds
 */
static int proc_apm_show(struct seq_file *m, void *v)
{
    struct apm_power_info info;
    char *units;

    info.ac_line_status = 0xff;
    info.battery_status = 0xff;
    info.battery_flag   = 0xff;
    info.battery_life   = -1;
    info.time       = -1;
    info.units      = -1;

    if (apm_get_power_status)
        apm_get_power_status(&info);

    switch (info.units) {
    default:    units = "?";    break;
    case 0:     units = "min";  break;
    case 1:     units = "sec";  break;
    }

    seq_printf(m, "%s 1.2 0x%02x 0x%02x 0x%02x 0x%02x %d%% %d %s\n",
             driver_version, APM_32_BIT_SUPPORT,
             info.ac_line_status, info.battery_status,
             info.battery_flag, info.battery_life,
             info.time, units);

    return 0;
}

static int proc_apm_open(struct inode *inode, struct file *file)
{
    return single_open(file, proc_apm_show, NULL);
}

static const struct file_operations apm_proc_fops = {
    .owner      = THIS_MODULE,
    .open       = proc_apm_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};
#endif

static int kapmd(void *arg)
{
    do {
        apm_event_t event;

        wait_event_interruptible(kapmd_wait,
                !queue_empty(&kapmd_queue) || kthread_should_stop());

        if (kthread_should_stop())
            break;

        spin_lock_irq(&kapmd_queue_lock);
        event = 0;
        if (!queue_empty(&kapmd_queue))
            event = queue_get_event(&kapmd_queue);
        spin_unlock_irq(&kapmd_queue_lock);

        switch (event) {
        case 0:
            break;

        case APM_LOW_BATTERY:
        case APM_POWER_STATUS_CHANGE:
            queue_event(event);
            break;

        case APM_USER_SUSPEND:
        case APM_SYS_SUSPEND:
            pm_suspend(PM_SUSPEND_MEM);
            break;

        case APM_CRITICAL_SUSPEND:
            atomic_inc(&userspace_notification_inhibit);
            pm_suspend(PM_SUSPEND_MEM);
            atomic_dec(&userspace_notification_inhibit);
            break;
        }
    } while (1);

    return 0;
}

static int apm_suspend_notifier(struct notifier_block *nb,
                unsigned long event,
                void *dummy)
{
    struct apm_user *as;
    int err;

    /* short-cut emergency suspends */
    if (atomic_read(&userspace_notification_inhibit))
        return NOTIFY_DONE;

    switch (event) {
    case PM_SUSPEND_PREPARE:
        /*
         * Queue an event to all "writer" users that we want
         * to suspend and need their ack.
         */
        mutex_lock(&state_lock);
        down_read(&user_list_lock);

        list_for_each_entry(as, &apm_user_list, list) {
            if (as->suspend_state != SUSPEND_WAIT && as->reader &&
                as->writer && as->suser) {
                as->suspend_state = SUSPEND_PENDING;
                atomic_inc(&suspend_acks_pending);
                queue_add_event(&as->queue, APM_USER_SUSPEND);
            }
        }

        up_read(&user_list_lock);
        mutex_unlock(&state_lock);
        wake_up_interruptible(&apm_waitqueue);

        /*
         * Wait for the the suspend_acks_pending variable to drop to
         * zero, meaning everybody acked the suspend event (or the
         * process was killed.)
         *
         * If the app won't answer within a short while we assume it
         * locked up and ignore it.
         */
        err = wait_event_interruptible_timeout(
            apm_suspend_waitqueue,
            atomic_read(&suspend_acks_pending) == 0,
            5*HZ);

        /* timed out */
        if (err == 0) {
            /*
             * Move anybody who timed out to "ack timeout" state.
             *
             * We could time out and the userspace does the ACK
             * right after we time out but before we enter the
             * locked section here, but that's fine.
             */
            mutex_lock(&state_lock);
            down_read(&user_list_lock);
            list_for_each_entry(as, &apm_user_list, list) {
                if (as->suspend_state == SUSPEND_PENDING ||
                    as->suspend_state == SUSPEND_READ) {
                    as->suspend_state = SUSPEND_ACKTO;
                    atomic_dec(&suspend_acks_pending);
                }
            }
            up_read(&user_list_lock);
            mutex_unlock(&state_lock);
        }

        /* let suspend proceed */
        if (err >= 0)
            return NOTIFY_OK;

        /* interrupted by signal */
        return notifier_from_errno(err);

    case PM_POST_SUSPEND:
        /*
         * Anyone on the APM queues will think we're still suspended.
         * Send a message so everyone knows we're now awake again.
         */
        queue_event(APM_NORMAL_RESUME);

        /*
         * Finally, wake up anyone who is sleeping on the suspend.
         */
        mutex_lock(&state_lock);
        down_read(&user_list_lock);
        list_for_each_entry(as, &apm_user_list, list) {
            if (as->suspend_state == SUSPEND_ACKED) {
                /*
                 * TODO: maybe grab error code, needs core
                 * changes to push the error to the notifier
                 * chain (could use the second parameter if
                 * implemented)
                 */
                as->suspend_result = 0;
                as->suspend_state = SUSPEND_DONE;
            }
        }
        up_read(&user_list_lock);
        mutex_unlock(&state_lock);

        wake_up(&apm_suspend_waitqueue);
        return NOTIFY_OK;

    default:
        return NOTIFY_DONE;
    }
}

static struct notifier_block apm_notif_block = {
    .notifier_call = apm_suspend_notifier,
};

static int __init apm_init(void)
{
    int ret;

    if (apm_disabled) {
        printk(KERN_NOTICE "apm: disabled on user request.\n");
        return -ENODEV;
    }

    kapmd_tsk = kthread_create(kapmd, NULL, "kapmd");
    if (IS_ERR(kapmd_tsk)) {
        ret = PTR_ERR(kapmd_tsk);
        kapmd_tsk = NULL;
        goto out;
    }
    wake_up_process(kapmd_tsk);

#ifdef CONFIG_PROC_FS
    proc_create("apm", 0, NULL, &apm_proc_fops);
#endif

    ret = misc_register(&apm_device);
    if (ret)
        goto out_stop;

    ret = register_pm_notifier(&apm_notif_block);
    if (ret)
        goto out_unregister;

    return 0;

 out_unregister:
    misc_deregister(&apm_device);
 out_stop:
    remove_proc_entry("apm", NULL);
    kthread_stop(kapmd_tsk);
 out:
    return ret;
}

static void __exit apm_exit(void)
{
    unregister_pm_notifier(&apm_notif_block);
    misc_deregister(&apm_device);
    remove_proc_entry("apm", NULL);

    kthread_stop(kapmd_tsk);
}

module_init(apm_init);
module_exit(apm_exit);

MODULE_AUTHOR("Stephen Rothwell");
MODULE_DESCRIPTION("Advanced Power Management");
MODULE_LICENSE("GPL");

#ifndef MODULE
static int __init apm_setup(char *str)
{
    while ((str != NULL) && (*str != '\0')) {
        if (strncmp(str, "off", 3) == 0)
            apm_disabled = 1;
        if (strncmp(str, "on", 2) == 0)
            apm_disabled = 0;
        str = strchr(str, ',');
        if (str != NULL)
            str += strspn(str, ", \t");
    }
    return 1;
}

__setup("apm=", apm_setup);
#endif

void apm_queue_event(apm_event_t event)
{
    unsigned long flags;

    spin_lock_irqsave(&kapmd_queue_lock, flags);
    queue_add_event(&kapmd_queue, event);
    spin_unlock_irqrestore(&kapmd_queue_lock, flags);

    wake_up_interruptible(&kapmd_wait);
}
EXPORT_SYMBOL(apm_queue_event);