LCD驱动移植之背光控制

移植环境

BootLoader：u-boot-1.1.6

kernel：linux-2.6.30.4

CPU：s3c2440

开发板：TQ2440

移植步骤

控制 LCD 背光的开关对于TQ2440 开发板来讲，就是控制S3C2440 的 LCD 控制的LCD_PWREN 脚，根据 S3C2440 的datasheet，可以知道在 LCDCON5 寄存器的 PWREN 位是控制 LCD 是否输出的，当为 0 时 LCD 不输出，此时 LCD_PWREN 脚为低，就会关闭 LCD 的背光；当为 1 时 LCD 输出，此时 LCD_PWREN 脚为高，开启 LCD 的背光。

1、编写LCD背光驱动

对于 Linux-2.6.30.4 的内核来讲，需要重新制作LCD 背光驱动，命名为：le2440_backlight.c，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 <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 <mach/fb.h>
#include <linux/cdev.h>

#define DEVICE_NAME	"backlight"

#define S3C2440_LCD_BASE		0x59000000
#define S3C2440_LCDCON1			(S3C2440_LCD_BASE + 0x00)
volatile int *lcdcon1 = NULL;


static int tq2440_backlight_ioctl(
	struct inode *inode, 
	struct file *file, 
	unsigned int cmd, 
	unsigned long arg)
{
	switch(cmd)
	{
		case 0:
			s3c2410_gpio_setpin(S3C2410_GPG4, 0);
			//*lcdcon1 = *lcdcon1 & (~(0x1<<0));
			printk("backlight Turn Off!\n");
			return 0;
		case 1:
			s3c2410_gpio_setpin(S3C2410_GPG4, 1);
			//*lcdcon1 |= (0x1<<0);
			printk("backlight Turn On!\n");
			return 0;
		default:
			return -EINVAL;
	}
}

static struct file_operations dev_fops = {
	.owner	=	THIS_MODULE,
	.ioctl	=	tq2440_backlight_ioctl
};

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

static int __init dev_init(void)
{
	int ret;

	lcdcon1 = (int *)ioremap(S3C2440_LCDCON1, 4);
	ret = misc_register(&misc);

	printk (DEVICE_NAME" initialized\n");

	s3c2410_gpio_cfgpin(S3C2410_GPG4, S3C2410_GPG4_OUTP);
	return ret;
}


static void __exit dev_exit(void)
{
	misc_deregister(&misc);
}

module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");

编写Makefile如下：

#Makefile 
ifeq ($(KERNELRELEASE),) 
	 
	 KERNELDIR ?= /home/linux/sky/ker/linux-2.6.30.4/ 
	 #KERNELDIR ?= /lib/modules/$(shell uname -r)/build 
PWD := $(shell pwd) 
 
modules: 
	    $(MAKE) -C $(KERNELDIR) M=$(PWD)  
		 
modules_install: 
	    $(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install 
		 
clean: 
	    rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions Module* modules* 
		 
.PHONY: modules modules_install clean 

else
	obj-m := le2440_backlight.o 
       
endif 

然后make，生成 le2440_backlight.ko 文件，拷贝到NFS文件系统中

2、编写应用程序控制LCD背光

编写应用程序backlight.c，代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/fb.h>
int main(int argc, char **argv)
{
	int turn;
	int fd;
	if ( argc == 1 )
{
	fprintf(stderr, "\nUsage: backlight on|off !\n\n");
	exit(1);
}
	fd = open("/dev/backlight", O_RDWR);
	if (fd < 0) {
	perror("open LCD device !");
	exit(1);
}

if ( strcmp(argv[1], "on" ) == 0)
	turn = 1;
	else if ( strcmp(argv[1], "off" ) == 0)
	turn = 0;
	else
{
	fprintf(stderr, "\nUsage: backlight on|off !\n\n");
	exit(1);
	}
		ioctl(fd, turn);
		close(fd);
		return 0;
}

编写Makefile，如下：

CROSS=arm-linux-
all: backlight
backlight:backlight.c
	$(CROSS)gcc -o backlight backlight.c
	$(CROSS)strip backlight
clean:
	@rm -vf backlight *.o *~

make生成可执行文件backlight，拷贝到NFS文件系统中

3、测试LCD背光

可看到LCD屏亮灭