/*
   * 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/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
  ");
  		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
  ",
  		     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;
  	unsigned long apm_event;
  
  	/* short-cut emergency suspends */
  	if (atomic_read(&userspace_notification_inhibit))
  		return NOTIFY_DONE;
  
  	switch (event) {
  	case PM_SUSPEND_PREPARE:
  	case PM_HIBERNATION_PREPARE:
  		apm_event = (event == PM_SUSPEND_PREPARE) ?
  			APM_USER_SUSPEND : APM_USER_HIBERNATION;
  		/*
  		 * 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_event);
  			}
  		}
  
  		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:
  	case PM_POST_HIBERNATION:
  		apm_event = (event == PM_POST_SUSPEND) ?
  			APM_NORMAL_RESUME : APM_HIBERNATION_RESUME;
  		/*
  		 * 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_event);
  
  		/*
  		 * 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.
  ");
  		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
  
  /**
   * 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);