LINUX LED驱动

LINUX LED驱动向用户空间提供/sys/class/leds/keyboard-backlight和/sys/class/leds/lcd-backlight接口

1，在/sys/class目录创建leds子目录

leds_class = class_create(THIS_MODULE, "leds");

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->suspend = led_suspend;
leds_class->resume = led_resume;
return 0;
}

2，在sys/class/leds/目录创建文件keyboard-backlight和lcd-backlight

led_cdev->dev = device_create(leds_class, parent, 0, led_cdev, "%s", led_cdev->name);

int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
{
int rc;

led_cdev->dev = device_create(leds_class, parent, 0, led_cdev,
"%s", led_cdev->name);
if (IS_ERR(led_cdev->dev))
return PTR_ERR(led_cdev->dev);

/* register the attributes */
rc = device_create_file(led_cdev->dev, &dev_attr_brightness);
if (rc)
goto err_out;

#ifdef CONFIG_LEDS_TRIGGERS
init_rwsem(&led_cdev->trigger_lock);
#endif
/* add to the list of leds */
down_write(&leds_list_lock);
list_add_tail(&led_cdev->node, &leds_list);
up_write(&leds_list_lock);

led_update_brightness(led_cdev);

#ifdef CONFIG_LEDS_TRIGGERS
rc = device_create_file(led_cdev->dev, &dev_attr_trigger);
if (rc)
goto err_out_led_list;

led_trigger_set_default(led_cdev);
#endif

printk(KERN_INFO "Registered led device: %s/n",
led_cdev->name);

return 0;

#ifdef CONFIG_LEDS_TRIGGERS
err_out_led_list:
device_remove_file(led_cdev->dev, &dev_attr_brightness);
list_del(&led_cdev->node);
#endif
err_out:
device_unregister(led_cdev->dev);
return rc;
}
EXPORT_SYMBOL_GPL(led_classdev_register);

3，创建 led_brightness的show和store接口

static void led_update_brightness(struct led_classdev *led_cdev)
{
if (led_cdev->brightness_get)
led_cdev->brightness = led_cdev->brightness_get(led_cdev);
}

static ssize_t led_brightness_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct led_classdev *led_cdev = dev_get_drvdata(dev);

/* no lock needed for this */
led_update_brightness(led_cdev);

return sprintf(buf, "%u/n", led_cdev->brightness);
}

static ssize_t led_brightness_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t size)
{
struct led_classdev *led_cdev = dev_get_drvdata(dev);
ssize_t ret = -EINVAL;
char *after;
unsigned long state = simple_strtoul(buf, &after, 10);
size_t count = after - buf;

if (*after && isspace(*after))
count++;

if (count == size) {
ret = count;

if (state == LED_OFF)
led_trigger_remove(led_cdev);
led_set_brightness(led_cdev, state);
}

return ret;
}

static DEVICE_ATTR(brightness, 0644, led_brightness_show, led_brightness_store);