LCD背光驱动(字符设备)在FL2440的开发(2.6.33.7内核)

一、开发环境
主 机：fedora 14 (2.6.33.7)
开发板：FL2440(nandflash:K9F1G08 128m)
编译器：arm-linux-gcc 4.3.2

二、原理分析
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，只要往GPG4口写入高电平，(1)则背光打开，写入低电平(0)则背光关闭。

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三、实现步骤
1. 编写背光驱动。文件名为fl2440_backlight.c

/*

*==============================================

*Name : fl2440_backlight.c

*Author : y.q.yang

*Date : 17/2/2011

*Copyright : GPL

*Description : fl2440 lcd backlight driver

*==============================================

*/

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/init.h>

#include <linux/errno.h>

#include <mach/hardware.h>

#include <mach/regs-gpio.h>

#include <mach/gpio-fns.h>

#include <mach/gpio-nrs.h>

#define DEVICE_NAME “fl2440_backlight”

#define DEVICE_MAJOR 230

#define BL_OFF 0

#define BL_ON 1

#define S3C2410_GPIONO(bank,offset) ((bank) + (offset))

#define S3C2410_GPIO_BANKG (32*6)

#define S3C2410_GPG4 S3C2410_GPIONO(S3C2410_GPIO_BANKG, 4)

static int bl_open(struct inode *inode, struct file *filp)

{

return 0;

}

static int bl_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg)

{

if(cmd<0 || cmd>1)

{

return -EINVAL;

}

switch(cmd)

{

case BL_ON:

{

s3c2410_gpio_setpin(S3C2410_GPG4,BL_ON);

printk(DEVICE_NAME ” turn on!\n”);

break;

}

case BL_OFF:

{

s3c2410_gpio_setpin(S3C2410_GPG4,BL_OFF);

printk(DEVICE_NAME ” turn off!\n”);

break;

}

default:

printk(“cmd default!\n”);

return -EINVAL;

}

return 0;

}

struct file_operations bl_fops =

{

.owner = THIS_MODULE,

.open = bl_open,

.ioctl = bl_ioctl,

};

static int __init bl_init(void)

{

int ret;

s3c2410_gpio_cfgpin(S3C2410_GPG4, 0×1 << 8);

s3c2410_gpio_setpin(S3C2410_GPG4, BL_ON);

ret = register_chrdev(DEVICE_MAJOR, DEVICE_NAME, &bl_fops);

if(ret<0)

{

printk(“register failed!\n”);

return ret;

}

return ret;

}

static void __exit bl_exit(void)

{

unregister_chrdev(DEVICE_MAJOR, DEVICE_NAME);

}

module_init(bl_init);

module_exit(bl_exit);

MODULE_LICENSE(“GPL”);

MODULE_AUTHOR(“y.q.yang”);

MODULE_DESCRIPTION(“FL2440 backlight driver”);

2. 把背光驱动代码部署到内核中去

#cp -f fl2440_backlight.c /linux-2.6.33.7/drivers/char //把驱动源码复制到内核驱动的字符设备下

#vim /linux-2.6.33.7/drivers/char/Kconfig //添加LCD背光设备配置

config FL2440_BACKLIGHT

tristate “FL2440 Backlight Device”

depends on ARCH_S3C2440

default y

---help---

FL2440 User Backlight

#vim /linux-2.6.33.7/drivers/char/Makefile //添加LCD背光设备配置

obj-$(CONFIG_FL2440_BACKLIGHT) += fl2440_backlight.o

3. 配置内核，选择LCD背光设备选项

#make menuconfig

Device Drivers --->

Character devices --->

<*> FL2440 Backlight Device (NEW)

4. 编译内核并下载到开发板上，查看已加载的设备：#cat /proc/devices，可以看到fl2440_backlight的主设备号为230

90 mtd

99 ppdev

116 alsa

128 ptm

136 pts

180 usb

188 ttyUSB

189 usb_device

204 s3c2410_serial

230 fl2440_backlight

231 fl2440_leds

232 fl2440_buttons

254 rtc

Block devices:

1 ramdisk

259 blkext

四、测试驱动

1.编写应用程序测试LED驱动，文件名：bl_test.c

/*

*==============================================

*Name : bl_test.c

*Author : y.q.yang

*Date : 17/2/2011

*Copyright : GPL

*Description : fl2440 lcd backlight test

*==============================================

*/

#include <stdio.h>

#include <stdlib.h>

#include <fcntl.h>

#include <sys/ioctl.h>

int main(int argc, char **argv)

{

int turn,fd;

if(argc == 1 || argc >2)

{

printf(“Usage: bl_test on|off\n”);

exit(1);

}

fd = open(“/dev/fl2440_backlight”, 0);

if(fd<0)

{

printf(“Open backlight device failed!\n”);

exit(1);

}

if(strcmp(argv[1], “on”) == 0)

{

turn = 1;

}

else if(strcmp(argv[1], “off”) == 0)

{

turn = 0;

}

else

{

printf(“Usage: bl_test on|off\n”);

exit(1);

}

ioctl(fd,turn);

close(fd);

return 0;

}

2. 在开发主机上交叉编译测试应用程序，并复制到文件系统的/usr/sbin目录下，然后重新编译文件系统下载到开发板上

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

3. 在开发板上的文件系统中创建一个背光设备的节点，然后运行测试程序，效果图如下，观测开发板上的LED灯，可以看到每一步的操作对应的LCD液晶屏会点亮或者熄灭

[root@yyq2440 /]# mknod /dev/fl2440_backlight c 230 0

[root@yyq2440 /]# bl_test –help

Usage: bl_test on|off

[root@yyq2440 /]# bl_test off

fl2440_backlight turn off

[root@yyq2440 /]# bl_test on

fl2440_backlight turn on

五、补充问题

暂无

From: http://www.w3c.com.cn/lcd%E8%83%8C%E5%85%89%E9%A9%B1%E5%8A%A8%E5%AD%97%E7%AC%A6%E8%AE%BE%E5%A4%87%E5%9C%A8fl2440%E7%9A%84%E5%BC%80%E5%8F%912-6-33-7%E5%86%85%E6%A0%B8