apm-emulation.c

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/*
 * bios-less APM driver for ARM Linux
 *  Jamey Hicks <[e-mail]>
 *  adapted from the APM BIOS driver for Linux by Stephen Rothwell ([e-mail])
 *
 * 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.
			 */