/* * 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/init.h> #include <linux/module.h> #include <linux/spinlock.h> #include <linux/mm.h> #include <linux/slab.h> #include <linux/pm.h> #include <linux/pm_legacy.h> #include <linux/interrupt.h> #include <linux/mutex.h> /* * 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 DEFINE_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 = kzalloc(sizeof(struct pm_dev), GFP_KERNEL); if (dev) { dev->type = type; dev->id = id; dev->callback = callback; mutex_lock(&pm_devs_lock); list_add(&dev->entry, &pm_devs); mutex_unlock(&pm_devs_lock); } return dev; } /** * 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 occurring in parallel * and conflicting. * * WARNING: Calling pm_send directly is not generally recommended, in * particular 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. */ static 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 occurring in parallel * and conflicting. */ int pm_send_all(pm_request_t rqst, void *data) { struct list_head *entry; mutex_lock(&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); mutex_unlock(&pm_devs_lock); return status; } } entry = entry->next; } mutex_unlock(&pm_devs_lock); return 0; } EXPORT_SYMBOL(pm_register); EXPORT_SYMBOL(pm_send_all);