嵌入式Linux之我行——LCD背光驱动在2440上的实例开发

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define DEVICE_NAME "backlight" //设备名称
#define DEVICE_MINOR 5 //次设备号，这里我们将设备注册为misc设备，这种设备的主设备号都为10

static int my2440_backlight_ioctl(struct inode *inode,

                                  struct file *file,

                                  unsigned int cmd,

                                  unsigned long arg)
{
    switch(cmd)
    {
        case 0:

            //当接收的命令为0时，就将GPG4引脚设为低电平，关闭背光
            s3c2410_gpio_setpin(S3C2410_GPG4, 0); 
            printk(DEVICE_NAME " turn off!\n");
            return 0;
        case 1:

            //当接收的命令为1时，就将GPG4引脚设为高电平，开启背光
            s3c2410_gpio_setpin(S3C2410_GPG4, 1); 
            printk(DEVICE_NAME " turn on!\n");
            return 0;
        default:
            return -EINVAL;
    }
}

static struct file_operations dev_fops = 
{
    .owner = THIS_MODULE,
    .ioctl = my2440_backlight_ioctl, //这里只使用控制IO口的方式来控制背光
};

static struct miscdevice misc =
{
    .minor = DEVICE_MINOR,
    .name = DEVICE_NAME,
    .fops = &dev_fops,
};

static int __init dev_init(void)
{
    int ret;

    ret = misc_register(&misc); //注册成misc设备

    if(ret < 0)
    {
        printk("Register misc device fiald!");
        return ret;
    }

    //将GPG4口配置成输出口
    s3c2410_gpio_cfgpin(S3C2410_GPG4, S3C2410_GPG4_OUTP); 

    return ret;
}

static void __exit dev_exit(void)
{
    misc_deregister(&misc); //注销该misc设备
}

module_init(dev_init);
module_exit(dev_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Huang Gang");
MODULE_DESCRIPTION("Backlight control for my2440");

#cp -f my2440_backlight.c linux-2.6.30.4/drivers/video/backlight/

#gedit linux-2.6.30.4/drivers/video/backlight/Kconfig

config MY2440_LCD_BACKLIGHT
    tristate "My2440 LCD Backlight Controls"
    depends on BACKLIGHT_LCD_SUPPORT
    default y

#gedit linux-2.6.30.4/drivers/video/backlight/Makefile

obj-$(CONFIG_MY2440_LCD_BACKLIGHT) += my2440_backlight.o

Device Drivers --->
    Graphics support ---> 
        [*] Backlight & LCD device support ---> 
            --- Backlight & LCD device support 
            <*> My2440 LCD Backlight Controls (NEW) 
            < > Lowlevel LCD controls 
            < > Lowlevel Backlight controls

#mknod /dev/backlight c 10 5

#include 
#include 
#include 
#include 

int main(int argc, char **argv)
{
    int turn;
    int fd;
    
    //检测命令后面带的参数
    if(argc == 1 || argc > 2)
    {
        printf("Usage: backlight on|off!\n");
        exit(1);
    }
    
    //打开背光设备
    fd = open("/dev/backlight", O_RDWR);
    
    if(fd < 0)
    {
        printf("Open Backlight Device Faild!\n");
        exit(1);
    }
    
    //判断输入的参数
    if(strcmp(argv[1], "on") == 0)
    {
        turn = 1;
    }
    else if(strcmp(argv[1], "off") == 0)
    {
        turn = 0;
    }
    else
    {
        printf("Usage: backlight on|off!\n");
        exit(1);
    }
    
    //进行IO控制
    ioctl(fd, turn);

    //关闭背光设备
    close(fd);

    return 0;
}

#arm-linux-gcc -o backlight_test backlight_test.c