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/*

 * bios-less APM driver for ARM Linux

 *  Jamey Hicks <jamey@crl.dec.com>

 *  adapted from the APM BIOS driver for Linux by Stephen Rothwell (sfr@linuxcare.com)

 *

 * 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/hwdev/busbios/amp_12.htm]

 */

#include <linux/module.h>

#include <linux/poll.h>

#include <linux/slab.h>

#include <linux/proc_fs.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>

#include <asm/system.h>

/*

 * The apm_bios device is one of the misc char devices.

 * This is its minor number.

 */

#define APM_MINOR_DEV   134

/*

 * See Documentation/Config.help for the configuration options.

 *

 * Various options can be changed at boot time as follows:

 * (We allow underscores for compatibility with the modules code)

 *      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];

};

/*

 * 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;

        unsigned int            suspend_state;

#define SUSPEND_NONE    0                /* no suspend pending */

#define SUSPEND_PENDING 1               /* suspend pending read */

#define SUSPEND_READ    2               /* suspend read, pending ack */

#define SUSPEND_ACKED   3               /* suspend acked */

#define SUSPEND_WAIT    4               /* waiting for suspend */

#define SUSPEND_DONE    5               /* suspend completed */

        struct apm_queue        queue;

};

/*

 * Local variables

 */

static int suspends_pending;

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);

}

/*

 * queue_suspend_event - queue an APM suspend event.

 *

 * Check that we're in a state where we can suspend.  If not,

 * return -EBUSY.  Otherwise, queue an event to all "writer"

 * users.  If there are no "writer" users, return '1' to

 * indicate that we can immediately suspend.

 */

static int queue_suspend_event(apm_event_t event, struct apm_user *sender)

{

        struct apm_user *as;

        int ret = 1;

        mutex_lock(&state_lock);

        down_read(&user_list_lock);

        /*

         * If a thread is still processing, we can't suspend, so reject

         * the request.

         */

        list_for_each_entry(as, &apm_user_list, list) {

                if (as != sender && as->reader && as->writer && as->suser &&

                    as->suspend_state != SUSPEND_NONE) {

                        ret = -EBUSY;

                        goto out;

                }

        }

        list_for_each_entry(as, &apm_user_list, list) {

                if (as != sender && as->reader && as->writer && as->suser) {

                        as->suspend_state = SUSPEND_PENDING;

                        suspends_pending++;

                        queue_add_event(&as->queue, event);

                        ret = 0;

                }

        }

 out:

        up_read(&user_list_lock);

        mutex_unlock(&state_lock);

        wake_up_interruptible(&apm_waitqueue);

        return ret;

}

static void apm_suspend(void)

{

        struct apm_user *as;

        int err = pm_suspend(PM_SUSPEND_MEM);

        /*

         * 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_WAIT ||

                    as->suspend_state == SUSPEND_ACKED) {

                        as->suspend_result = err;

                        as->suspend_state = SUSPEND_DONE;

                }

        }

        up_read(&user_list_lock);

        mutex_unlock(&state_lock);

        wake_up(&apm_suspend_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 int

apm_ioctl(struct inode * inode, 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;

                if (as->suspend_state == SUSPEND_READ) {

                        int pending;

                        /*

                         * 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;

                        suspends_pending--;

                        pending = suspends_pending == 0;

                        mutex_unlock(&state_lock);

                        /*

                         * If there are no further acknowledges required,

                         * suspend the system.

                         */

                        if (pending)

                                apm_suspend();

                        /*

                         * Wait for the suspend/resume to complete.  If there

                         * are pending acknowledges, we wait here for them.

                         */

                        freezer_do_not_count();

                        wait_event(apm_suspend_waitqueue,

                                   as->suspend_state == SUSPEND_DONE);

                        /*

                         * Since we are waiting until the suspend is done, the

                         * try_to_freeze() in freezer_count() will not trigger

                         */

                        freezer_count();

                } else {

                        as->suspend_state = SUSPEND_WAIT;

                        mutex_unlock(&state_lock);

                        /*

                         * Otherwise it is a request to suspend the system.

                         * Queue an event for all readers, and expect an

                         * acknowledge from all writers who haven't already

                         * acknowledged.

                         */

                        err = queue_suspend_event(APM_USER_SUSPEND, as);

                        if (err < 0) {

                                /*

                                 * Avoid taking the lock here - this

                                 * should be fine.

                                 */

                                as->suspend_state = SUSPEND_NONE;

                                break;

                        }

                        if (err > 0)

                                apm_suspend();

                        /*

                         * Wait for the suspend/resume to complete.  If there

                         * are pending acknowledges, we wait here for them.

                         */

                        wait_event_freezable(apm_suspend_waitqueue,

                                         as->suspend_state == SUSPEND_DONE);

                }

                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;

        int pending = 0;

        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.  However, we

         * need to balance suspends_pending, which means the

         * possibility of sleeping.

         */

        mutex_lock(&state_lock);

        if (as->suspend_state != SUSPEND_NONE) {

                suspends_pending -= 1;

                pending = suspends_pending == 0;

        }

        mutex_unlock(&state_lock);

        if (pending)

                apm_suspend();

        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 struct file_operations apm_bios_fops = {

        .owner          = THIS_MODULE,

        .read           = apm_read,

        .poll           = apm_poll,

        .ioctl          = apm_ioctl,

        .open           = apm_open,

        .release        = apm_release,

};

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 apm_get_info(char *buf, char **start, off_t fpos, int length)

{

        struct apm_power_info info;

        char *units;

        int ret;

        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;

        }

        ret = sprintf(buf, "%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 ret;

}

#endif

static int kapmd(void *arg)

{

        do {

                apm_event_t event;

                int ret;

                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:

                        ret = queue_suspend_event(event, NULL);

                        if (ret < 0) {

                                /*

                                 * We were busy.  Try again in 50ms.

                                 */

                                queue_add_event(&kapmd_queue, event);

                                msleep(50);

                        }

                        if (ret > 0)

                                apm_suspend();

                        break;

                case APM_CRITICAL_SUSPEND:

                        apm_suspend();

                        break;

                }

        } while (1);

        return 0;

}

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;

                return ret;

        }

        wake_up_process(kapmd_tsk);

#ifdef CONFIG_PROC_FS

        create_proc_info_entry("apm", 0, NULL, apm_get_info);

#endif

        ret = misc_register(&apm_device);

        if (ret != 0) {

                remove_proc_entry("apm", NULL);

                kthread_stop(kapmd_tsk);

        }

        return ret;

}

static void __exit apm_exit(void)

{

        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

/**

 * apm_queue_event - queue an APM event for kapmd

 * @event: APM event

 *

 * Queue an APM event for kapmd to process and ultimately take the

 * appropriate action.  Only a subset of events are handled:

 *   %APM_LOW_BATTERY

 *   %APM_POWER_STATUS_CHANGE

 *   %APM_USER_SUSPEND

 *   %APM_SYS_SUSPEND

 *   %APM_CRITICAL_SUSPEND

 */

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);