android leds简单代码总结

linux leds

【源码：linux-3.2-rc7】

关于led，前两天被问道一个问题，这里顺便总结下吧。

led，对于我们所有的人来说这是一个比较简单的模块，当然也是学习时比较好入口的一个模块。

分析驱动，都了解先看Makefile &Kconfig

# LED Core

obj-$(CONFIG_NEW_LEDS) += led-core.o

obj-$(CONFIG_LEDS_CLASS) += led-class.o

obj-$(CONFIG_LEDS_TRIGGERS) += led-triggers.o

# LED Platform Drivers

obj-$(CONFIG_LEDS_88PM860X) += leds-88pm860x.o

obj-$(CONFIG_LEDS_ATMEL_PWM) += leds-atmel-pwm.o

obj-$(CONFIG_LEDS_S3C24XX) += leds-s3c24xx.o

............

# LED SPI Drivers

obj-$(CONFIG_LEDS_DAC124S085) += leds-dac124s085.o

# LED Triggers

obj-$(CONFIG_LEDS_TRIGGER_HEARTBEAT) += ledtrig-heartbeat.o

obj-$(CONFIG_LEDS_TRIGGER_BACKLIGHT) += ledtrig-backlight.o

.........

再来看看Kconfig对这些宏的定义

先看看NEW_LEDS

bool"LED Support"

help

Say Y to enable Linux LED support. This allows control of supported

LEDs from both userspace and optionally, bykernel events (triggers).

This is not related to standard keyboard LEDswhich are controlled

via the input system.

configLEDS_CLASS

bool"LED Class Support"

help

This option enables the led sysfs class in/sys/class/leds. You'll

need this to do anything useful withLEDs. If unsure, say N.

configLEDS_TRIGGERS

bool"LED Trigger support"

dependson LEDS_CLASS

help

This option enables trigger support for theleds class.

These triggers allow kernel events to drivethe LEDs and can

be configured via sysfs. If unsure, say Y.

看了上面的解释，大家也都有一个基本的了解了，这里我们拿2410的例子来解释。

makefile中定义

obj-$(CONFIG_LEDS_S3C24XX) += leds-s3c24xx.o

Kconfig中定义

config LEDS_S3C24XX

tristate"LED Support for Samsung S3C24XX GPIO LEDs"

dependson LEDS_CLASS

dependson ARCH_S3C2410

help

This option enables support for LEDsconnected to GPIO lines

on Samsung S3C24XX series CPUs, such as theS3C2410 and S3C2440.

在Kconfig中，我们注意到使用leds-s3c24xx.c需要打开LEDS_CLASS，并且依赖于ARCH S3C2410。

下面我们分析具体的代码

代码路径linux-3.2-rc7/drivers/leds/leds-s3c24xx.c

static inline struct s3c24xx_gpio_led*pdev_to_gpio(struct platform_device *dev)

static inline struct s3c24xx_gpio_led*to_gpio(struct led_classdev *led_cdev)

static void s3c24xx_led_set(structled_classdev *led_cdev,

enum led_brightness value)

static int s3c24xx_led_remove(structplatform_device *dev)

static int s3c24xx_led_probe(structplatform_device *dev)

{

structs3c24xx_led_platdata *pdata = dev->dev.platform_data;

structs3c24xx_gpio_led *led;

intret;

led= kzalloc(sizeof(struct s3c24xx_gpio_led), GFP_KERNEL);

if(led == NULL) {

dev_err(&dev->dev,"No memory for device\n");

return-ENOMEM;

}

platform_set_drvdata(dev,led);

led->cdev.brightness_set= s3c24xx_led_set;

led->cdev.default_trigger= pdata->def_trigger;

led->cdev.name= pdata->name;

led->cdev.flags|= LED_CORE_SUSPENDRESUME;

led->pdata= pdata;

/*no point in having a pull-up if we are always driving */

if(pdata->flags & S3C24XX_LEDF_TRISTATE) {

s3c2410_gpio_setpin(pdata->gpio,0);

s3c2410_gpio_cfgpin(pdata->gpio,S3C2410_GPIO_INPUT);

}else {

s3c2410_gpio_pullup(pdata->gpio,0);

s3c2410_gpio_setpin(pdata->gpio,0);

s3c2410_gpio_cfgpin(pdata->gpio,S3C2410_GPIO_OUTPUT);

}

/*register our new led device */

ret= led_classdev_register(&dev->dev, &led->cdev);

if(ret < 0) {

dev_err(&dev->dev,"led_classdev_register failed\n");

kfree(led);

returnret;

}

return0;

}

static struct platform_drivers3c24xx_led_driver = {

.probe = s3c24xx_led_probe,

.remove = s3c24xx_led_remove,

.driver = {

.name = "s3c24xx_led",

.owner = THIS_MODULE,

};

static int __init s3c24xx_led_init(void)

{

returnplatform_driver_register(&s3c24xx_led_driver);

}

static void __exit s3c24xx_led_exit(void)

{

platform_driver_unregister(&s3c24xx_led_driver);

}

这里可以看到整个的驱动是一个简单的设备注册的过程，只不过这里对led的注册的时候出现了led_classdev_register这样的注册的方式。

在leds-class.txt中找到的对其的简单的描述如下：

In its simplest form, the LED class justallows control of LEDs from

userspace. LEDs appear in /sys/class/leds/.

在Android中的基本的框架图是：

在android的手机中可以看到如上的分布

R,G,B三色LED，button-backlight，keyboard-backlight，lcd-backlight，torch-flash。而这里的spotlight则要根据你具体的外设看有没有了。

Have Fun！

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