Linux ドライバー | ドライバーで sysfs インターフェイスを作成

//灯灭
echo 0 >/sys/class/leds/firefly:blue:power/brightness 
//灯亮
echo 1 >/sys/class/leds/firefly:blue:power/brightness

static DEVICE_ATTR(led_status, 0600, led_status_show, led_status_store);

static unsigned int led = 0;
/*
*  sys节点的读函数
*  执行 cat /sys/devices/platform/leds/led_status时会调用
*/
static ssize_t led_status_show(struct device *dev, struct device_attribute *attr, char *buf)
{
  //buf是通过cat命令显示到终端的内容，这里显示led变量
 return sprintf(buf, "%s:%d.\n", "led", led);
}

/**
*  sys节点的写函数
*  用echo命令往sys节点写入内容时，会调用该函数
*/
static ssize_t led_status_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
  //写入的内容会存放到buf中，这里将buf内容赋值给led变量
 sscanf(buf, "%d", &led);

 return count;
}

static struct attribute *led_attributes[]={
 
  /*上述使用了DEVICE_ATTR声明节点名字为led_status，
  * 则struct attribute名字应为：
  *  dev_attr_ + (节点名) + .attr
  * 所以名字为dev_attr_led_status.attr
  */
  &dev_attr_led_status.attr,
 NULL,
};


static const struct attribute_group led_attrs={
 .attrs = led_attributes,//引用上述struct attribute数组
};

 leds:leds{
  compatible = "xx,xx-led";
 };

static unsigned int led = 0;

static ssize_t led_status_show(struct device *dev, struct device_attribute *attr, char *buf)
{
 return sprintf(buf, "%s:%d.\n", "led", led);
}

static ssize_t led_status_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
 sscanf(buf, "%d", &led);

 return count;
}

static DEVICE_ATTR(led_status, 0600, led_status_show, led_status_store);

static struct attribute *led_attributes[]={
 &dev_attr_led_status.attr,
 NULL,
};


static const struct attribute_group led_attrs={
 .attrs = led_attributes,
};

static int xx_led_probe(struct platform_device *pdev)
{
 sysfs_create_group(&pdev->dev.kobj, &led_attrs);
 return 0;
}

static int xx_led_remove(struct platform_device *pdev)
{
 sysfs_remove_group(&pdev->dev.kobj, &led_attrs);
 return 0;
}

static const struct of_device_id xx_led_of_match[] = {
 {.compatible = "xx,xx-led"},
};


static struct platform_driver xx_led_driver = {
 .probe = xx_led_probe,
 .remove = xx_led_remove,
 .driver = {
  .name = "xx-led",
  .owner = THIS_MODULE,
  .of_match_table = xx_led_of_match,
 },
};

static int __init xx_led_init(void)
{
 return platform_driver_register(&xx_led_driver );
}

static void __exit xx_led_exit(void)
{
 platform_driver_unregister(&xx_led_driver);
}

module_init(xx_led_init);
module_exit(xx_led_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("xx led driver");
MODULE_AUTHOR("Vincent");
MODULE_VERSION("V1.0.00");

//查看led变量的值
cat /sys/devices/platform/leds/led_status
led:0.

//修改led变量的值为9
echo 9 > /sys/devices/platform/leds/led_status
//查看
cat /sys/devices/platform/leds/led_status
led:9.