/* kernel/power/earlysuspend.c
*
* Copyright (C) 2005-2008 Google, Inc.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* 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.
*
*/
#include <linux/earlysuspend.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/rtc.h>
#include <linux/wakelock.h>
#include <linux/workqueue.h>
#include "power.h"
enum {
DEBUG_USER_STATE = 1U << ,
DEBUG_SUSPEND = 1U << ,
DEBUG_VERBOSE = 1U << ,
};
static int debug_mask = DEBUG_USER_STATE;
module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
static DEFINE_MUTEX(early_suspend_lock);
static LIST_HEAD(early_suspend_handlers);
static void early_suspend(struct work_struct *work);
static void late_resume(struct work_struct *work);
static DECLARE_WORK(early_suspend_work, early_suspend);
static DECLARE_WORK(late_resume_work, late_resume);
static DEFINE_SPINLOCK(state_lock);
enum {
SUSPEND_REQUESTED = 0x1,
SUSPENDED = 0x2,
SUSPEND_REQUESTED_AND_SUSPENDED = SUSPEND_REQUESTED | SUSPENDED,
};
static int state;
void register_early_suspend(struct early_suspend *handler)
{
struct list_head *pos;
mutex_lock(&early_suspend_lock);
list_for_each(pos, &early_suspend_handlers) {
struct early_suspend *e;
e = list_entry(pos, struct early_suspend, link);
if (e->level > handler->level)
break;
}
list_add_tail(&handler->link, pos);
if ((state & SUSPENDED) && handler->suspend)
handler->suspend(handler);
mutex_unlock(&early_suspend_lock);
}
EXPORT_SYMBOL(register_early_suspend);
void unregister_early_suspend(struct early_suspend *handler)
{
mutex_lock(&early_suspend_lock);
list_del(&handler->link);
mutex_unlock(&early_suspend_lock);
}
EXPORT_SYMBOL(unregister_early_suspend);
register_early_suspend(struct early_suspend *handler)会按照level从小到大的方式，将handler依次挂在early_suspend_handlers链表头上。
if (e->level > handler->level)判断链表节点e的level大于要插入的handler的level时就break当前遍历，用list_add_tail(&handler->link, pos);将handler->link插到pos节点的前面。
static void early_suspend(struct work_struct *work)
{
struct early_suspend *pos;
unsigned long irqflags;
int abort = ;
mutex_lock(&early_suspend_lock);
spin_lock_irqsave(&state_lock, irqflags);
if (state == SUSPEND_REQUESTED)
state |= SUSPENDED;
else
abort = ;
spin_unlock_irqrestore(&state_lock, irqflags);
if (abort) {
if (debug_mask & DEBUG_SUSPEND)
pr_info("early_suspend: abort, state %d\n", state);
mutex_unlock(&early_suspend_lock);
goto abort;
}
if (debug_mask & DEBUG_SUSPEND)
pr_info("early_suspend: call handlers\n");
list_for_each_entry(pos, &early_suspend_handlers, link) {
if (pos->suspend != NULL) {
if (debug_mask & DEBUG_VERBOSE)
pr_info("early_suspend: calling %pf\n", pos->suspend);
pos->suspend(pos);
}
}
mutex_unlock(&early_suspend_lock);
suspend_sys_sync_queue();
abort:
spin_lock_irqsave(&state_lock, irqflags);
if (state == SUSPEND_REQUESTED_AND_SUSPENDED)
wake_unlock(&main_wake_lock);
spin_unlock_irqrestore(&state_lock, irqflags);
}
static void late_resume(struct work_struct *work)
{
struct early_suspend *pos;
unsigned long irqflags;
int abort = ;
mutex_lock(&early_suspend_lock);
spin_lock_irqsave(&state_lock, irqflags);
if (state == SUSPENDED)
state &= ~SUSPENDED;
else
abort = ;
spin_unlock_irqrestore(&state_lock, irqflags);
if (abort) {
if (debug_mask & DEBUG_SUSPEND)
pr_info("late_resume: abort, state %d\n", state);
goto abort;
}
if (debug_mask & DEBUG_SUSPEND)
pr_info("late_resume: call handlers\n");
list_for_each_entry_reverse(pos, &early_suspend_handlers, link) {
if (pos->resume != NULL) {
if (debug_mask & DEBUG_VERBOSE)
pr_info("late_resume: calling %pf\n", pos->resume);
pos->resume(pos);
}
}
if (debug_mask & DEBUG_SUSPEND)
pr_info("late_resume: done\n");
abort:
mutex_unlock(&early_suspend_lock);
}
early_suspend(struct work_struct *work)和late_resume(struct work_struct *work)分别在第37、38行被声明为了early_suspend_work和late_resume_work，以便在
request_suspend_state(suspend_state_t new_state)中的suspend_work_queue工作队列中使用。
ealry_suspend(struct work_struct *work)中最关键的一句list_for_each_entry(pos, &early_suspend_handlers, link)，表示按照level等级排列的顺序，依次调用pos所指向的各个
驱动中注册的ealrysuspend 指向的suspend handler。
late_resume(struct work_struct *work)中list_for_each_entry_reverse(pos, &early_suspend_handlers, link)，表示按照level等级的逆序，依次调用pos所指向的各个
驱动中注册的earlysuspend 指向的resume handler。
这里有一个很有用的调试信息：pr_info("late_resume: calling %pf\n", pos->resume); %pf可以打印被调函数的函数名。
void request_suspend_state(suspend_state_t new_state)
{
unsigned long irqflags;
int old_sleep;
spin_lock_irqsave(&state_lock, irqflags);
old_sleep = state & SUSPEND_REQUESTED;
if (debug_mask & DEBUG_USER_STATE) {
struct timespec ts;
struct rtc_time tm;
getnstimeofday(&ts);
rtc_time_to_tm(ts.tv_sec, &tm);
pr_info("request_suspend_state: %s (%d->%d) at %lld "
"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
new_state != PM_SUSPEND_ON ? "sleep" : "wakeup",
requested_suspend_state, new_state,
ktime_to_ns(ktime_get()),
tm.tm_year + , tm.tm_mon + , tm.tm_mday,
tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
}
if (!old_sleep && new_state != PM_SUSPEND_ON) {
state |= SUSPEND_REQUESTED;
queue_work(suspend_work_queue, &early_suspend_work);
} else if (old_sleep && new_state == PM_SUSPEND_ON) {
state &= ~SUSPEND_REQUESTED;
wake_lock(&main_wake_lock);
queue_work(suspend_work_queue, &late_resume_work);
}
requested_suspend_state = new_state;
spin_unlock_irqrestore(&state_lock, irqflags);
}
suspend_state_t get_suspend_state(void)
{
return requested_suspend_state;
}
request_suspend_state(suspend_state_t new_state)会被kernel/power/main.c中的state show调用，main.c将会在下一章详细说明。
request_suspend_state(suspend_state_t new_state)传入的参数new_state的类型suspend_state_t为一个typedef类型的变量：typedef int __bitwise suspend_state_t;
当new_state为0时，request_suspend_state调用queue_work(suspend_work_queue, &late_resume_work);分支进行late唤醒。
当new_state为3时，request_suspend_state调用queue_work(suspend_work_queue, &early_suspend_work);分支进行浅度休眠。
当系统休眠/唤醒时，串口上会出现如下打印：
request_suspend_state: sleep (0->3) at 6442598858519 (2012-02-05 01:31:08.172285684 UTC)
request_suspend_state: wakeup (3->0) at 6464854624023 (2012-02-05 01:31:30.428053438 UTC)
0代表唤醒，3代表休眠。
0->3 从唤醒到休眠(sleep);
3->0 从休眠到唤醒(wakeup);
