/*
 *  pm.c - Power management interface
 *
 *  Copyright (C) 2000 Andrew Henroid
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/pm.h>
#include <linux/interrupt.h>

int pm_active;

/*
 *      Locking notes:
 *              pm_devs_lock can be a semaphore providing pm ops are not called
 *      from an interrupt handler (already a bad idea so no change here). Each
 *      change must be protected so that an unlink of an entry doesn't clash
 *      with a pm send - which is permitted to sleep in the current architecture
 *
 *      Module unloads clashing with pm events now work out safely, the module 
 *      unload path will block until the event has been sent. It may well block
 *      until a resume but that will be fine.
 */
 
static DECLARE_MUTEX(pm_devs_lock);
static LIST_HEAD(pm_devs);

/**
 *      pm_register - register a device with power management
 *      @type: device type 
 *      @id: device ID
 *      @callback: callback function
 *
 *      Add a device to the list of devices that wish to be notified about
 *      power management events. A &pm_dev structure is returned on success,
 *      on failure the return is %NULL.
 *
 *      The callback function will be called in process context and
 *      it may sleep.
 */
 
struct pm_dev *pm_register(pm_dev_t type,
                           unsigned long id,
                           pm_callback callback)
{
        struct pm_dev *dev = kmalloc(sizeof(struct pm_dev), GFP_KERNEL);
        if (dev) {
                memset(dev, 0, sizeof(*dev));
                dev->type = type;
                dev->id = id;
                dev->callback = callback;

                down(&pm_devs_lock);
                list_add(&dev->entry, &pm_devs);
                up(&pm_devs_lock);
        }
        return dev;
}

/**
 *      pm_unregister -  unregister a device with power management
 *      @dev: device to unregister
 *
 *      Remove a device from the power management notification lists. The
 *      dev passed must be a handle previously returned by pm_register.
 */
 
void pm_unregister(struct pm_dev *dev)
{
        if (dev) {
                down(&pm_devs_lock);
                list_del(&dev->entry);
                up(&pm_devs_lock);

                kfree(dev);
        }
}

static void __pm_unregister(struct pm_dev *dev)
{
        if (dev) {
                list_del(&dev->entry);
                kfree(dev);
        }
}

/**
 *      pm_unregister_all - unregister all devices with matching callback
 *      @callback: callback function pointer
 *
 *      Unregister every device that would call the callback passed. This
 *      is primarily meant as a helper function for loadable modules. It
 *      enables a module to give up all its managed devices without keeping
 *      its own private list.
 */
 
void pm_unregister_all(pm_callback callback)
{
        struct list_head *entry;

        if (!callback)
                return;

        down(&pm_devs_lock);
        entry = pm_devs.next;
        while (entry != &pm_devs) {
                struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
                entry = entry->next;
                if (dev->callback == callback)
                        __pm_unregister(dev);
        }
        up(&pm_devs_lock);
}

/**
 *      pm_send - send request to a single device
 *      @dev: device to send to
 *      @rqst: power management request
 *      @data: data for the callback
 *
 *      Issue a power management request to a given device. The 
 *      %PM_SUSPEND and %PM_RESUME events are handled specially. The
 *      data field must hold the intended next state. No call is made
 *      if the state matches.
 *
 *      BUGS: what stops two power management requests occuring in parallel
 *      and conflicting.
 *
 *      WARNING: Calling pm_send directly is not generally recommended, in
 *      paticular there is no locking against the pm_dev going away. The
 *      caller must maintain all needed locking or have 'inside knowledge'
 *      on the safety. Also remember that this function is not locked against
 *      pm_unregister. This means that you must handle SMP races on callback
 *      execution and unload yourself.
 */
 
int pm_send(struct pm_dev *dev, pm_request_t rqst, void *data)
{
        int status = 0;
        unsigned long prev_state, next_state;

        if (in_interrupt())
                BUG();

        switch (rqst) {
        case PM_SUSPEND:
        case PM_RESUME:
                prev_state = dev->state;
                next_state = (unsigned long) data;
                if (prev_state != next_state) {
                        if (dev->callback)
                                status = (*dev->callback)(dev, rqst, data);
                        if (!status) {
                                dev->state = next_state;
                                dev->prev_state = prev_state;
                        }
                }
                else {
                        dev->prev_state = prev_state;
                }
                break;
        default:
                if (dev->callback)
                        status = (*dev->callback)(dev, rqst, data);
                break;
        }
        return status;
}

/*
 * Undo incomplete request
 */
static void pm_undo_all(struct pm_dev *last)
{
        struct list_head *entry = last->entry.prev;
        while (entry != &pm_devs) {
                struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
                if (dev->state != dev->prev_state) {
                        /* previous state was zero (running) resume or
                         * previous state was non-zero (suspended) suspend
                         */
                        pm_request_t undo = (dev->prev_state
                                             ? PM_SUSPEND:PM_RESUME);
                        pm_send(dev, undo, (void*) dev->prev_state);
                }
                entry = entry->prev;
        }
}

/**
 *      pm_send_all - send request to all managed devices
 *      @rqst: power management request
 *      @data: data for the callback
 *
 *      Issue a power management request to a all devices. The 
 *      %PM_SUSPEND events are handled specially. Any device is 
 *      permitted to fail a suspend by returning a non zero (error)
 *      value from its callback function. If any device vetoes a 
 *      suspend request then all other devices that have suspended 
 *      during the processing of this request are restored to their
 *      previous state.
 *
 *      WARNING:  This function takes the pm_devs_lock. The lock is not dropped until
 *      the callbacks have completed. This prevents races against pm locking
 *      functions, races against module unload pm_unregister code. It does
 *      mean however that you must not issue pm_ functions within the callback
 *      or you will deadlock and users will hate you.
 *
 *      Zero is returned on success. If a suspend fails then the status
 *      from the device that vetoes the suspend is returned.
 *
 *      BUGS: what stops two power management requests occuring in parallel
 *      and conflicting.
 */
 
int pm_send_all(pm_request_t rqst, void *data)
{
        struct list_head *entry;
        
        down(&pm_devs_lock);
        entry = pm_devs.next;
        while (entry != &pm_devs) {
                struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
                if (dev->callback) {
                        int status = pm_send(dev, rqst, data);
                        if (status) {
                                /* return devices to previous state on
                                 * failed suspend request
                                 */
                                if (rqst == PM_SUSPEND)
                                        pm_undo_all(dev);
                                up(&pm_devs_lock);
                                return status;
                        }
                }
                entry = entry->next;
        }
        up(&pm_devs_lock);
        return 0;
}

/**
 *      pm_find  - find a device
 *      @type: type of device
 *      @from: where to start looking
 *
 *      Scan the power management list for devices of a specific type. The
 *      return value for a matching device may be passed to further calls
 *      to this function to find further matches. A %NULL indicates the end
 *      of the list. 
 *
 *      To search from the beginning pass %NULL as the @from value.
 *
 *      The caller MUST hold the pm_devs_lock lock when calling this 
 *      function. The instant that the lock is dropped all pointers returned
 *      may become invalid.
 */
 
struct pm_dev *pm_find(pm_dev_t type, struct pm_dev *from)
{
        struct list_head *entry = from ? from->entry.next:pm_devs.next;
        while (entry != &pm_devs) {
                struct pm_dev *dev = list_entry(entry, struct pm_dev, entry);
                if (type == PM_UNKNOWN_DEV || dev->type == type)
                        return dev;
                entry = entry->next;
        }
        return 0;
}

EXPORT_SYMBOL(pm_register);
EXPORT_SYMBOL(pm_unregister);
EXPORT_SYMBOL(pm_unregister_all);
EXPORT_SYMBOL(pm_send);
EXPORT_SYMBOL(pm_send_all);
EXPORT_SYMBOL(pm_find);
EXPORT_SYMBOL(pm_active);