/*
 * bios-less APM driver for hp680
 *
 * Copyright 2005 (c) Andriy Skulysh <askulysh@gmail.com>
 *
 * based on ARM APM driver by
 *  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/timer.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/miscdevice.h>
#include <linux/apm_bios.h>
#include <linux/pm.h>
#include <linux/pm_legacy.h>
#include <asm/apm.h>

#define MODNAME "apm"

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

/*
 * 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_DONE	4		/* suspend completed */

	struct apm_queue	queue;
};

/*
 * Local variables
 */
static int suspends_pending;

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 DECLARE_COMPLETION(kapmd_exit);
static DEFINE_SPINLOCK(kapmd_queue_lock);
static struct apm_queue kapmd_queue;

int apm_suspended;
EXPORT_SYMBOL(apm_suspended);

/* Platform-specific apm_read_proc(). */
int (*apm_get_info)(char *buf, char **start, off_t fpos, int length);
EXPORT_SYMBOL(apm_get_info);

/*
 * 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_one_user(struct apm_user *as, apm_event_t event)
{
	if (as->suser && as->writer) {
		switch (event) {
		case APM_SYS_SUSPEND:
		case APM_USER_SUSPEND:
			/*
			 * If this user already has a suspend pending,
			 * don't queue another one.
			 */
			if (as->suspend_state != SUSPEND_NONE)
				return;

			as->suspend_state = SUSPEND_PENDING;
			suspends_pending++;
			break;
		}
	}
	queue_add_event(&as->queue, event);
}

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

	down_read(&user_list_lock);

	list_for_each_entry(as, &apm_user_list, list)
		if (as != sender && as->reader)
			queue_event_one_user(as, event);

	up_read(&user_list_lock);
	wake_up_interruptible(&apm_waitqueue);
}

/**
 * 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)
{
	spin_lock_irq(&kapmd_queue_lock);
	queue_add_event(&kapmd_queue, event);
	spin_unlock_irq(&kapmd_queue_lock);

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

static void apm_suspend(void)
{
	struct apm_user *as;
	int err;

	apm_suspended = 1;
	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, NULL);

	/*
	 * Finally, wake up anyone who is sleeping on the suspend.
	 */
	down_read(&user_list_lock);
	list_for_each_entry(as, &apm_user_list, list) {
		as->suspend_result = err;
		as->suspend_state = SUSPEND_DONE;
	}
	up_read(&user_list_lock);

	wake_up(&apm_suspend_waitqueue);
	apm_suspended = 0;
}

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;

		if (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND)
			as->suspend_state = SUSPEND_READ;

		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;
	unsigned long flags;
	int err = -EINVAL;

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

	switch (cmd) {
	case APM_IOC_SUSPEND:
		as->suspend_result = -EINTR;

		if (as->suspend_state == 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;
			suspends_pending--;
		} else {
			/*
			 * 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.
			 */
			queue_event(APM_USER_SUSPEND, as);
		}

		/*
		 * If there are no further acknowledges required, suspend
		 * the system.
		 */
		if (suspends_pending == 0)
			apm_suspend();

		/*
		 * Wait for the suspend/resume to complete.  If there are
		 * pending acknowledges, we wait here for them.
		 *
		 * Note that we need to ensure that the PM subsystem does
		 * not kick us out of the wait when it suspends the threads.
		 */
		flags = current->flags;
		current->flags |= PF_NOFREEZE;

		/*
		 * Note: do not allow a thread which is acking the suspend
		 * to escape until the resume is complete.
		 */
		if (as->suspend_state == SUSPEND_ACKED)
			wait_event(apm_suspend_waitqueue,
					 as->suspend_state == SUSPEND_DONE);
		else
			wait_event_interruptible(apm_suspend_waitqueue,
					 as->suspend_state == SUSPEND_DONE);

		current->flags = flags;
		err = as->suspend_result;
		as->suspend_state = SUSPEND_NONE;
		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.  However, we
	 * need to balance suspends_pending, which means the
	 * possibility of sleeping.
	 */
	if (as->suspend_state != SUSPEND_NONE) {
		suspends_pending -= 1;
		if (suspends_pending == 0)
			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_read_proc(char *buf, char **start, off_t fpos, int length)
{
	if (likely(apm_get_info))
		return apm_get_info(buf, start, fpos, length);

	return -EINVAL;
}
#endif

static int kapmd(void *arg)
{
	daemonize("kapmd");
	current->flags |= PF_NOFREEZE;

	do {
		apm_event_t event;

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

		if (!pm_active)
			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, NULL);
			break;

		case APM_USER_SUSPEND:
		case APM_SYS_SUSPEND:
			queue_event(event, NULL);
			if (suspends_pending == 0)
				apm_suspend();
			break;

		case APM_CRITICAL_SUSPEND:
			apm_suspend();
			break;
		}
	} while (1);

	complete_and_exit(&kapmd_exit, 0);
}

static int __init apm_init(void)
{
	int ret;

	pm_active = 1;

	ret = kernel_thread(kapmd, NULL, CLONE_KERNEL);
	if (unlikely(ret < 0)) {
		pm_active = 0;
		return ret;
	}

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

	ret = misc_register(&apm_device);
	if (unlikely(ret != 0)) {
		remove_proc_entry("apm", NULL);

		pm_active = 0;
		wake_up(&kapmd_wait);
		wait_for_completion(&kapmd_exit);
	}

	return ret;
}

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

	pm_active = 0;
	wake_up(&kapmd_wait);
	wait_for_completion(&kapmd_exit);
}

module_init(apm_init);
module_exit(apm_exit);

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