mini2440驱动-lcd背光灯

1、硬件原理图分析。由原理图得知LCD的背光是由2440的GPG4口控制的


2、在 linux-2.6.39/drivers/video/backlight/目录下，创建my2440_backlight.c文件，代码内容如下：

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/serio.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>

#include <asm/io.h>
#include <asm/irq.h>
#include <asm/uaccess.h>
#include <mach/regs-clock.h>
#include <plat/regs-timer.h>

#include <mach/regs-gpio.h>
#include <linux/cdev.h>
#include "my2440_backlight.h"

#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 file *file, unsigned int cmd, unsigned long arg)
{

    switch(cmd)
    {
        case BL_OFF:
            //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_GPG(4), 0);
        printk(DEVICE_NAME " turn off!\n");
            return 0;
        case BL_ON:
            //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_GPG(4), 1);
            printk(DEVICE_NAME " turn on!\n");
            return 0;
        default:
        printk("error cmd\n");
            return -EINVAL;
    }
}

static struct file_operations dev_fops =
{
    .owner = THIS_MODULE,
    .unlocked_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_GPG(4), S3C2410_GPIO_OUTPUT);

    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("lisi");
MODULE_DESCRIPTION("Backlight control for my2440");

在 linux-2.6.39/drivers/video/backlight/目录下，创建my2440_backlight.h文件，代码内容如下：
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#define BL_MAGIC 'B'
#define BL_ON _IO(BL_MAGIC,0)
#define BL_OFF _IO(BL_MAGIC,1)

修改backlight/目录下的Kconfig文件，添加背光选项

#gedit linux-2.6.39/drivers/video/backlight/Kconfig

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

修改backlight/目录下的Makefile文件，在最后一行添加

#gedit linux-2.6.39/drivers/video/backlight/Makefile

obj-$(CONFIG_MY2440_LCD_BACKLIGHT) += my2440_backlight.o

配置内核选项，选中上面添加的配置项

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

3、编写测试代码backlight_test.c，，使用交叉编译工具进行静态编译，内容如下：
#arm-linux-gcc -static backlight_test.c -o backlight_test
点击(此处)折叠或打开

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include "my2440_backlight.h"

int main(int argc, char **argv)
{
    int fd;
    int cmd;

    if(argc <2)
    {
     printf("Please enter the sencond para!\n");
        return 0;
    }

    cmd = atoi(argv[1]);

    fd = open("/dev/backlight1",O_RDWR);

    if(cmd == 1)
    {
        ioctl(fd,BL_ON);
    }
    else if(cmd == 0)
    {
        ioctl(fd,BL_OFF);
    }
    return 0;
}

4、测试结果如下：