24_GPIO读

itop4412学习记录

本章的目的： 掌握gpio的申请、配置、取值和释放。

（1）gpio申请：gpio_request
（2）gpio配置-设置为输入：s3c_gpio_cfgpin(EXYNOS4_GPC0(3),S3C_GPIO_INPUT); 
（3）gpio配置-设置为非上下拉：s3c_gpio_setpull(EXYNOS4_GPC0(3),S3C_GPIO_PULL_NONE);
（4）gpio取值：gpio_get_value
（5）gpio释放：gpio_free(EXYNOS4_GPC0(3));

1. 驱动设计思路

1.1 输入IO选取

利用拨码开关来实现GPIO的输入，通过原理图理清楚拨码开关的3和4对应的IO编号：

管脚编号 → GPIO编号 → 对应GPIO虚拟地址宏
AP_SLEEP→GPC0_3→EXYNOS4_GPC0(3)    
XEINT6→GPX0_6→EXYNOS4_GPX0(6)
    
开关3和4，向内是低电平，输入0。向外是高电平1.8v，输入1。

开关3和4对应IO口需要做的准备： 1.设置为输入；2.不上拉，不下拉；3. 读寄存器
 

1.2 GPIO配置函数

（1）gpio申请：
gpio_request(EXYNOS4_GPC0(3),"GPC0_3");
gpio_request(EXYNOS4_GPX0(6),"GPX0_6");
（2）gpio配置-设置为输入：
s3c_gpio_cfgpin(EXYNOS4_GPC0(3),S3C_GPIO_INPUT); 
s3c_gpio_cfgpin(EXYNOS4_GPX0(6),S3C_GPIO_INPUT);
（3）gpio配置-设置为非上下拉：
s3c_gpio_setpull(EXYNOS4_GPC0(3),S3C_GPIO_PULL_NONE);
s3c_gpio_setpull(EXYNOS4_GPX0(6),S3C_GPIO_PULL_NONE);
（4）gpio取值：
gpio_get_value(EXYNOS4_GPC0(3));
gpio_get_value(EXYNOS4_GPX0(6));
（5）gpio释放：
gpio_free(EXYNOS4_GPC0(3));
gpio_free(EXYNOS4_GPX0(6));

1.3 设备注册

方法一： 在4412平台文件注册设备结构体：

iTop4412_Kernel_3.0/arch/arm/mach-exynos/mach-itop4412.c

    struct platform_device s3c_device_read_gpio_ctl = {
        .name   = "read_gpio_ctl",
        .id     = -1,
    };
     &s3c_device_read_gpio_ctl,

具体参考：06_设备注册

方法二：使用platform_device_register注册设备

#define DRIVER_NAME "gpio_read"
#define DEVICE_NAME "gpio_read_dev"

static int gpio_read_dev_release(struct platform_device *dev)
{
	printk("\tgpio read device.dec.release!!\n");
}

static struct platform_device s3c_device_gpio_read_dev = {
        .name   = DRIVER_NAME,
        .id             = -1,
		.dev = {
			.release = gpio_read_dev_release,
	}

};


Devicestate = platform_device_register(&s3c_device_gpio_read_dev);

参考：linux以module方式注册设备和注册驱动、以及杂项设备

推荐使用方法二，因为通用性强。

2. 代码调试

2.1 代码的编译

模块编译命令：make

应用程序编译命令：arm-none-linux-gnueabi-gcc -o user_read_gpio user_read_gpio.c

2.2 代码调试

（1）加载模块，查看设备节点

[root@iTOP-4412]# insmod gpio_read.ko
[  454.284761]  start gpio init!
[  454.309519] device state is 0 
[  454.311541]  gpio initialized
[  454.371292]  gpio init OK,DriverState is 0!
通过命令 ls /dev，可以发现设备节点：gpio_read_dev。

（2）运行程序程序gpio_read_dev

命令格式：./gpio_read_dev cmd

cmd=0时，读EXYNOS4_GPC0(3)

cmd=1时，读EXYNOS4_GPX0(6)

将开关4接地：

[root@iTOP-4412]# ./user_read_gpio 1
[  466.340700] gpio open
[  466.341593] cmd is 1,arg is 0
[  466.345198] gpio release
cmd is 1,gpio_read is 0

将开关4接1.8V：

[root@iTOP-4412]# ./user_read_gpio 1
[  503.834045] gpio open
[  503.834934] cmd is 1,arg is 0
[  503.838668] gpio release
cmd is 1,gpio_read is 1

3. 驱动代码

（1）gpio_read.c

#include 
#include 

/*驱动注册的头文件，包含驱动的结构体和注册和卸载的函数*/
#include 
/*注册杂项设备头文件*/
#include 
/*注册设备节点的文件结构体*/
#include 

/*Linux中申请GPIO的头文件*/
#include 
/*三星平台的GPIO配置函数头文件*/
/*三星平台EXYNOS系列平台，GPIO配置参数宏定义头文件*/
#include 
#include 

#define DRIVER_NAME "gpio_read"
#define DEVICE_NAME "gpio_read_dev"

static long gpio_ioctl( struct file *files, unsigned int cmd, unsigned long arg){
	printk("cmd is %d,arg is %d\n",cmd,arg);
	if(cmd > 1){
		printk(KERN_EMERG "cmd is 0 or 1\n");
	}
	if(arg > 1){
		printk(KERN_EMERG "arg is only 1\n");
	}
	
	if(cmd==0)
		return gpio_get_value(EXYNOS4_GPC0(3));
	if(cmd==1)
		return gpio_get_value(EXYNOS4_GPX0(6));
}

static int gpio_release(struct inode *inode, struct file *file){
	printk(KERN_EMERG "gpio release\n");
	return 0;
}

static int gpio_open(struct inode *inode, struct file *file){
	printk(KERN_EMERG "gpio open\n");
	return 0;
}

static struct file_operations gpio_ops = {
	.owner = THIS_MODULE,
	.open = gpio_open,
	.release = gpio_release,
	.unlocked_ioctl = gpio_ioctl,
};

static  struct miscdevice gpio_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = DEVICE_NAME,
	.fops = &gpio_ops,
};

static int gpio_probe(struct platform_device *pdv){
	int ret;	
	printk(KERN_EMERG "\tgpio initialized\n");
	
	ret = gpio_request(EXYNOS4_GPC0(3),"GPC0_3");	
	if(ret < 0){
		printk(KERN_EMERG "gpio_request EXYNOS4_GPC0(3) failed!\n");
		return ret;
	}
	
	ret = gpio_request(EXYNOS4_GPX0(6),"GPX0_6");	
	if(ret < 0){
		printk(KERN_EMERG "gpio_request EXYNOS4_GPX0(6) failed!\n");
		return ret;
	}	
	
	s3c_gpio_cfgpin(EXYNOS4_GPC0(3),S3C_GPIO_INPUT);	
	s3c_gpio_setpull(EXYNOS4_GPC0(3),S3C_GPIO_PULL_NONE);
	
	s3c_gpio_cfgpin(EXYNOS4_GPX0(6),S3C_GPIO_INPUT);	
	s3c_gpio_setpull(EXYNOS4_GPX0(6),S3C_GPIO_PULL_NONE);
	
	misc_register(&gpio_dev);	
	return 0;
}

static int gpio_remove(struct platform_device *pdv){
	printk(KERN_EMERG "\tgpio removed!\n");
	misc_deregister(&gpio_dev);
	return 0;
}

static void gpio_shutdown(struct platform_device *pdv){
	;
}

static int gpio_suspend(struct platform_device *pdv,pm_message_t pmt){
	return 0;
}

static int gpio_resume(struct platform_device *pdv){
	return 0;
}
static int gpio_read_dev_release(struct platform_device *dev)
{
	printk("\tgpio read device.dec.release!!\n");
}

static struct platform_device s3c_device_gpio_read_dev = {
        .name   = DRIVER_NAME,
        .id             = -1,
		.dev = {
			.release = gpio_read_dev_release,
	}

};


struct platform_driver gpio_driver = {
	.probe = gpio_probe,
	.remove = gpio_remove,
	.shutdown = gpio_shutdown,
	.suspend = gpio_suspend,
	.resume = gpio_resume,
	.driver = {
		.name = DRIVER_NAME,
		.owner = THIS_MODULE,
	}
};

static int gpio_init(void)
{
	int DriverState=0,Devicestate=0;	
	printk(KERN_EMERG "\tstart gpio init!\n");
	
	Devicestate = platform_device_register(&s3c_device_gpio_read_dev);
	printk(KERN_EMERG "device state is %d \n",Devicestate);
	
	DriverState = platform_driver_register(&gpio_driver);
	if(DriverState==0)
	{
		printk(KERN_EMERG "\tgpio init OK,DriverState is %d!\n",DriverState);
	}	
	
	return 0;
}

static void gpio_exit(void)
{
	printk(KERN_EMERG "gpio module exit!\n");
	platform_device_unregister(&s3c_device_gpio_read_dev);	
	platform_driver_unregister(&gpio_driver);	
	gpio_free(EXYNOS4_GPC0(3));
	gpio_free(EXYNOS4_GPX0(6));
}
module_init(gpio_init);
module_exit(gpio_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("TOPEET");

（2）user_read_gpio.c

#include 

#include 
#include 
#include 
#include 
#include 

int main(int agc,char **argv){
	int fd,cmd;
	char *hello_node = "/dev/gpio_read_dev";
	
	if(strcmp(argv[1],"0")==0) 
		cmd=0;
	if(strcmp(argv[1],"1")==0) 
		cmd=1;
	if(cmd > 1)printf("cmd must be 0 or 1!\n");
	
/*O_RDWR只读打开,O_NDELAY非阻塞方式*/	
if((cmd ==0)|(cmd ==1)){
	if((fd = open(hello_node,O_RDWR|O_NDELAY))<0){
		printf("APP open %s failed\n",hello_node);
	}
	else{
		printf("cmd is %d,gpio_read is %d\n",cmd,ioctl(fd,cmd,0));
		
	}
	close(fd);
}
	
}

（3）Makefile

#!/bin/bash
obj-m += gpio_read.o
KDIR := /home/topeet/iTop4412_Kernel_3.0
PWD ?= $(shell pwd)
all:
	make -C $(KDIR) M=$(PWD) modules
clean:
	rm -rf *.o

4. 收获

学会使用函数platform_device_register在模块中注册设备