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 <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>
#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。