linux 2.6.32 在arm9（s3c2440）平台的移植 - LCD背光驱动

LCD背光是通过 CPU的 LCD_PWR引脚来控制的, 当LCD_PWR输出1, 亮 , 输出0则灭.

以下的代码均参考mini2440的移植手册

(1)新建/drivers/video/mini2440_backlight.c

#include

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#include

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#undef DEBUG

#ifdef DEBUG

#define DPRINTK(x...) {printk(__FUNCTION__"(%d): ",__LINE__);printk(##x);}

#else

#define DPRINTK(x...) (void)(0)

#endif

#define DEVICE_NAME "backlight"

static unsigned int bl_state;

static inline void set_bl(int state)

{

        bl_state = !!state;

        s3c2410_gpio_setpin(S3C2410_GPG(4), bl_state);

}

static inline unsigned int get_bl(void)

{

         return bl_state;

}

static ssize_t dev_write(struct file *file, const char *buffer, size_t count, loff_t * ppos)

{

        unsigned char ch;

        int ret;

        if (count == 0) {

                return count;

        }

        ret = copy_from_user(&ch, buffer, sizeof ch)?-EFAULT:0;

        if (ret) {

                return ret;

        }

        ch &= 0x01;

        set_bl(ch);

        return count;

}

static ssize_t dev_read(struct file *filp, char *buffer, size_t count, loff_t *ppos)

{

        int ret;

        unsigned char str[] = {'0', '1' };

        if (count == 0) {

                return 0;

        }

        ret = copy_to_user(buffer, str + get_bl(), sizeof(unsigned char) ) ? -EFAULT : 0;

        if (ret) {

                return ret;

        }

        return sizeof(unsigned char);

}

static struct file_operations dev_fops = {

        owner: THIS_MODULE,

        read:dev_read,

        write: dev_write,

};

static struct miscdevice misc = {

        .minor = MISC_DYNAMIC_MINOR,

        .name = DEVICE_NAME,

        .fops = &dev_fops,

};

static int __init dev_init(void)

{

        int ret;

        ret = misc_register(&misc);

        printk (DEVICE_NAME"/tinitialized/n");

        s3c2410_gpio_cfgpin(S3C2410_GPG(4), S3C2410_GPIO_OUTPUT);

        set_bl(1);

        return ret;

}

static void __exit dev_exit(void)

{

        misc_deregister(&misc);

}

module_init(dev_init);

module_exit(dev_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("FriendlyARM Inc.");

(2)编辑同级目录(drivers/video/)的Kconfig, 找到config FB_S3C2410_DEBUG ,在下面添加:

config BACKLIGHT_MINI2440 

        tristate "Backlight support for mini2440 from FriendlyARM" 

        depends on FB_S3C2410 #这里注释掉&& FB_S3C2410 

        help 

          backlight driver for MINI2440 from FriendlyARM 

(3) 编辑同级目录(drivers/video)的Makefile, 找到obj-$(CONFIG_VIDEO_OUTPUT_CONTROL) += output.o, 在下面添加:

obj-$(CONFIG_BACKLIGHT_MINI2440) += mini2440_backlight.o

(4)然后再初级目录make menuconfig,在

Device Drivers  --->

   Graphics support  --->

      <*> Support for frame buffer devices  --->  

               [*]Backlight support for mini2440 from FriendlyARM

然后make zImage, 测试, ok,

(5) 使用方式

在命令行种输入：echo 0 > /dev/backlight 可以关闭LCD背光。

在命令行种输入：echo 1 > /dev/backlight 可以打开LCD背光。