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apm-emulation.c

/*
 * 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);

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