時代不同了，連led都成子系統了，針對內核提供的通用模型，分析一下，好久沒寫文章了也！
代碼位於drivers/leds下，看一下Makefile 模型文件主要是：
# LED Core
obj-$(CONFIG_LEDS_CLASS) += led-class.o
obj-$(CONFIG_LEDS_TRIGGERS) += led-triggers.o
直接看led-core文件吧，這個文件無比個性，主體內容四行
DECLARE_RWSEM(leds_list_lock);
EXPORT_SYMBOL_GPL(leds_list_lock);
LIST_HEAD(leds_list); //鏈接所有led的全局鏈表
EXPORT_SYMBOL_GPL(leds_list);
再來看下led-class.c函數，這裡先來介紹一下描述led的核心結構體
struct led_classdev {
const char *name; //名字
int brightness; //亮度值，也可以用來表示開關特性
int max_brightness; //允許的最大亮度值
int flags; //標志
/* Lower 16 bits reflect status */
#define LED_SUSPENDED (1 << 0)
/* Upper 16 bits reflect control information */
#define LED_CORE_SUSPENDRESUME (1 << 16)
/* Set LED brightness level */
/* Must not sleep, use a workqueue if needed */
void (*brightness_set)(struct led_classdev *led_cdev, //核心回調函數，當設置/sys/class/leds/下的led接口裡的brightness屬性文件時，會回調該函數
enum led_brightness brightness);
/* Get LED brightness level */
enum led_brightness (*brightness_get)(struct led_classdev *led_cdev); //核心回調函數，當獲得led當前值時會調用
/* Activate hardware accelerated blink, delays are in
* miliseconds and if none is provided then a sensible default
* should be chosen. The call can adjust the timings if it can't
* match the values specified exactly. */
int (*blink_set)(struct led_classdev *led_cdev,
unsigned long *delay_on,
unsigned long *delay_off);
struct device *dev; //嵌入的標准設備模型
struct list_head node; /* LED Device list */ //上面提到的全局led設備的掛接點
const char *default_trigger; /* Trigger to use */
#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;
#endif
};
好了，下面說下初始化函數：
static int __init leds_init(void)
