linux 2.6.32 在arm9（s3c2440）平台的移植 - LCD背光驱动

最新推荐文章于 2021-05-15 00:57:03 发布

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本文介绍了一个用于mini2440开发板LCD背光控制的Linux驱动程序实现方法，包括驱动文件的创建、配置选项的添加及如何通过命令行控制背光状态。

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。