1.[Leds]-(Linux leds class睡眠唤醒)

1.led_classdev 结构体
kernel/include/linux/leds.h

struct led_classdev {
	const char		*name; 
	enum led_brightness	 brightness;
	enum led_brightness	 max_brightness;
	int			 flags;     

	/* Lower 16 bits reflect status */
#define LED_SUSPENDED		(1 << 0)
	/* Upper 16 bits reflect control information */
#define LED_CORE_SUSPENDRESUME	(1 << 16)
#define LED_BLINK_ONESHOT	(1 << 17)
#define LED_BLINK_ONESHOT_STOP	(1 << 18)
#define LED_BLINK_INVERT	(1 << 19)
#define LED_SYSFS_DISABLE	(1 << 20)
#define SET_BRIGHTNESS_ASYNC	(1 << 21)
#define SET_BRIGHTNESS_SYNC	(1 << 22)
#define LED_DEV_CAP_FLASH	(1 << 23)

	/* Set LED brightness level */
	/* Must not sleep, use a workqueue if needed */
	void		(*brightness_set)(struct led_classdev *led_cdev,
					  enum led_brightness brightness);
	/*
	 * Set LED brightness level immediately - it can block the caller for
	 * the time required for accessing a LED device register.
	 */
	int		(*brightness_set_sync)(struct led_classdev *led_cdev,
					enum led_brightness brightness);
	/* Get LED brightness level */
	enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);

	/*
	 * Activate hardware accelerated blink, delays are in milliseconds
	 * and if both are zero then a sensible default should be chosen.
	 * The call should adjust the timings in that case and if it can't
	 * match the values specified exactly.
	 * Deactivate blinking again when the brightness is set to a fixed
	 * value via the brightness_set() callback.
	 */
	int		(*blink_set)(struct led_classdev *led_cdev,
				     unsigned long *delay_on,
				     unsigned long *delay_off);

	struct device		*dev;
	const struct attribute_group	**groups;

	struct list_head	 node;			/* LED Device list */
	const char		*default_trigger;	/* Trigger to use */

	unsigned long		 blink_delay_on, blink_delay_off;
	struct timer_list	 blink_timer;
	int			 blink_brightness;
	void			(*flash_resume)(struct led_classdev *led_cdev);

	struct work_struct	set_brightness_work;
	int			delayed_set_value;

#ifdef CONFIG_LEDS_TRIGGERS
	/* Protects the trigger data below */
	struct rw_semaphore	 trigger_lock;

	struct led_trigger	*trigger;
	struct list_head	 trig_list;
	void			*trigger_data;
	/* true if activated - deactivate routine uses it to do cleanup */
	bool			activated;
#endif

	/* Ensures consistent access to the LED Flash Class device */
	struct mutex		led_access;
};

2.kernel/drivers/leds/led-class.c

2.1 初始化时，创建类和绑定PM（power Manager）相关函数，绑定的是类PM，所以休眠/唤醒的时候，
	该类下的所有device都会调用led_suspend和led_resume ,对于某个led_classdev需不需要睡眠，
	由led_classdev中的flag位LED_CORE_SUSPENDRESUME决定)
	
#ifdef CONFIG_PM_SLEEP
//睡眠
static int led_suspend(struct device *dev)
{
	struct led_classdev *led_cdev = dev_get_drvdata(dev);

	if (led_cdev->flags & LED_CORE_SUSPENDRESUME)
		led_classdev_suspend(led_cdev);

	return 0;
}

//唤醒
static int led_resume(struct device *dev)
{
	struct led_classdev *led_cdev = dev_get_drvdata(dev);

	if (led_cdev->flags & LED_CORE_SUSPENDRESUME)
		led_classdev_resume(led_cdev);

	return 0;
}
#endif
static SIMPLE_DEV_PM_OPS(leds_class_dev_pm_ops, led_suspend, led_resume);

//初始化并绑定class PM
static int __init leds_init(void)
{
	leds_class = class_create(THIS_MODULE, "leds");
	if (IS_ERR(leds_class))
		return PTR_ERR(leds_class);
	leds_class->pm = &leds_class_dev_pm_ops;
	leds_class->dev_groups = led_groups;
	return 0;
}