驱动-----GPIO子系统

子系统：就是linux封装了很多函数，操作gpio，iic等

所以在使用的时候引脚可以调用系统的接口

先定义一个引脚

定义：

led1_init:

这里相当于把引脚资源申请了一下：

然后设置引脚的功能为输出：

int level就是输出高低电平，所以前面定义一个宏

led1_on和led1_off:

前面init里面request申请了一个资源，要释放掉，封装一个释放的函数。

最后在注销的时候调用这个函数

led_gpio子系统代码如下：

	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/types.h>
	#include <linux/fs.h>
	#include <linux/module.h>
	#include <linux/kdev_t.h>
	#include <linux/cdev.h>
	#include <asm/string.h>
	#include <asm/io.h>
	#include <asm/uaccess.h>
	#include <mach/gpio-nrs.h>
	#include <mach/gpio.h>
	#include <linux/miscdevice.h>

	#define DEV_NAME "led1"
	#define GPBCON 0x56000010
	#define GPBDAT 0x56000014
	#define GPIO_LED S3C2410_GPB(5)
	#define LED_ON 0
	#define LED_OFF 1

	static void led1_init(void)
	{
		gpio_request(GPIO_LED, "gpio_led");		
		gpio_direction_output(GPIO_LED, LED_OFF);
	}

	static void led1_on(void)
	{
		gpio_set_value(GPIO_LED, LED_ON);
	}

	static void led1_off(void)
	{
		gpio_set_value(GPIO_LED, LED_OFF);
	}

	static void led1_deinit(void)
	{
		gpio_free(GPIO_LED);
	}

	static int open(struct inode * node, struct file * file)
	{
		led1_init();
		printk("led open...\n");
		return 0;
	}

	static ssize_t read(struct file * file, char __user * buf, size_t len, loff_t * offset)
	{
		//copy_to_user();
		printk("led read...\n");
		return 0;
	}

	static ssize_t write(struct file * file, const char __user * buf, size_t len, loff_t * offset)
	{
		// "ledon"   on    "ledoff"   off
		unsigned char data[100] = {0};
		size_t cp_len = sizeof(data) < len ? sizeof(data) : len;
		copy_from_user(data, buf, cp_len);

		if(!strncmp(data, "ledon", strlen("ledon")))
			led1_on();
		else if(!strncmp(data, "ledoff", strlen("ledoff")))
			led1_off();

		printk("led write...\n");
		return cp_len;
	}

	static int close(struct inode * node, struct file * file)
	{
		led1_deinit();
		printk("led close...\n");
		return 0;
	}

	static struct file_operations fops = 
	{
		.owner = THIS_MODULE,
		.open = open,
		.read = read,
		.write = write,
		.release = close
	};

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

	static int __init led_init(void)
	{
		int ret = misc_register(&misc);
		if(ret < 0)
			goto err_misc_register;

		printk("led_init  ##########################\n");
		return ret;

	err_misc_register:
		printk("led misc_register failed #################\n");
		misc_deregister(&misc);
		return ret;
	}

	static void __exit led_exit(void)
	{
		misc_deregister(&misc);
		printk("led_exit  ##########################\n");
	}

	module_init(led_init);
	module_exit(led_exit);