大家好，又见面了，我是你们的朋友全栈君。
（1）添加头文件：
#include “core.h”
在core.h文件中有：
#ifdef CONFIG_HAS_EARLYSUSPEND
#include <linux/earlysuspend.h>
#endif
（2）在wifi驱动ath6kl结构体中添加early_suspend结构：
#ifdef CONFIG_HAS_EARLYSUSPEND
struct early_suspend early_suspend;
bool screen_off;
#endif
（3）在wifi驱动的电源管理文件pm.c中填充early_suspend结构体，并将其向android电源管理系统注册：
#ifdef CONFIG_HAS_EARLYSUSPEND
ar->screen_off = false;
ar->early_suspend.suspend = ath6kl_early_suspend;
ar->early_suspend.resume = ath6kl_late_resume;
ar->early_suspend.level = EARLY_SUSPEND_LEVEL_BLANK_SCREEN;
register_early_suspend(&ar->early_suspend);
#endif
所有注册到系统中的early_suspend结构都会按level值按顺序加入到全局链表early_suspend_handlers中。
希望执行early suspend的设备，他的设备驱动程序需要向电源管理系统注册，该结构体用于向电源管理系统注册earlysuspend/lateresume，当电源管理系统启动suspend流程时，回调函数suspend会被调用，相反，resume的最后阶段，回调函数resume会被调用，level字段用于调整该结构体在注册链表中的位置，suspend时，level的数值越小，回调函数的被调用的时间越早，resume时则反过来。
Android在earlysuspend.h中预先定义了3个level等级：
enum {
EARLY_SUSPEND_LEVEL_BLANK_SCREEN = 50,
EARLY_SUSPEND_LEVEL_STOP_DRAWING = 100,
EARLY_SUSPEND_LEVEL_DISABLE_FB = 150,
};
具体请见附件kernel/include/linux/earlysuspend.h
（4）在wifi驱动电源管理文件pm.c中取消early_suspend结构体的注册：
#ifdef CONFIG_HAS_EARLYSUSPEND
unregister_early_suspend(&ar->early_suspend);
#endif
（5）定义相关suspend和resume函数：
#ifdef CONFIG_HAS_EARLYSUSPEND
static void ath6kl_early_suspend(struct early_suspend *handler) { struct ath6kl *ar = container_of(handler, struct ath6kl, early_suspend); if (ar) ar->screen_off = true; } static void ath6kl_late_resume(struct early_suspend *handler) { struct ath6kl *ar = container_of(handler, struct ath6kl, early_suspend); if (ar) ar->screen_off = false; } #endif 附：kernel/include/linux/earlysuspend.h #ifndef _LINUX_EARLYSUSPEND_H #define _LINUX_EARLYSUSPEND_H #ifdef CONFIG_HAS_EARLYSUSPEND #include <linux/list.h> #endif /* The early_suspend structure defines suspend and resume hooks to be called * when the user visible sleep state of the system changes, and a level to * control the order. They can be used to turn off the screen and input * devices that are not used for wakeup. * Suspend handlers are called in low to high level order, resume handlers are * called in the opposite order. If, when calling register_early_suspend, * the suspend handlers have already been called without a matching call to the * Suspend handlers are called in low to high level order, resume handlers are * called in the opposite order. If, when calling register_early_suspend, * the suspend handlers have already been called without a matching call to the * resume handlers, the suspend handler will be called directly from * register_early_suspend. This direct call can violate the normal level order. */ enum { EARLY_SUSPEND_LEVEL_BLANK_SCREEN = 50, EARLY_SUSPEND_LEVEL_STOP_DRAWING = 100, EARLY_SUSPEND_LEVEL_DISABLE_FB = 150, }; struct early_suspend { #ifdef CONFIG_HAS_EARLYSUSPEND struct list_head link; int level; void (*suspend)(struct early_suspend *h); void (*resume)(struct early_suspend *h); #endif }; #ifdef CONFIG_HAS_EARLYSUSPEND void register_early_suspend(struct early_suspend *handler); void unregister_early_suspend(struct early_suspend *handler); #else #define register_early_suspend(handler) do { } while (0) #define unregister_early_suspend(handler) do { } while (0) #endif #endif
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