Linux_kernel字符设备驱动12

一、字符设备的编程框架

在Linux_kernel驱动开发11中，我们介绍的系统调用。只是为了做一个实验，在真正开发时，我们并不会直接在内核中添加一个新的系统调用，这样做会导致内核体积变大。

1、字符设备结构体

我们实现一个硬件字符设备的驱动程序，实际上是实例化一个struct cdev类型的对象。

【1】struct cdev; // 存储字符设备的相关信息

注意：

在该结构体中，我们只需关注这两个成员，其他的成员由内核自己维护

【 2**】dev_t dev; // 指示当前的设备号**

【3】const struct file_operations *ops; // 操作函数的集合

1）设备号

【1】区分主次设备号

设备号(32bit) = 主设备号(12bit [msb])+ 次设备号(20bit [lsb])

1】示例

ls -l /dev/tty0

主次设备号的范围理论上都是**[0, 255]**

主设备号：区分不同类型的设备

次设备号：区分同一类型设备的不同个体

MINORBITS：次设备号的位数

MINORMASK：次设备号掩码

MAJOR(dev)：得到主设备号

MINOR(dev)：得到次设备号

MKDEV(ma,mi)：将主设备号与次设备号合为一个32bit整型数（dev_t）

【2】静态注册设备号

就是自己先挑一个没有被内核占用的设备号去注册

0】查看被内核占用的设备号

cat /proc/devices

1】register_chrdev_region（注册设备号）

注释：

from：要注册的起始设备号

count：要连续注册的设备号个数

name：给设备起的名称

2】unregister_chrdev_region（注销设备号）

注释：

from：要注销的起始设备号

count：要连续注销的设备号个数

【3】静态注册实验

1】进入工程目录

cd /home/zjd/s5p6818/KERNEL/drivers

2】创建新的工程

mkdir chrdev

3】编写程序

vim chrdev.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>

#define CHRDEV_MAGOR	200
#define CHRDEV_MINOR	10
#define CHRDEV_NUM		1
#define CHRDEV_NAME		"leds"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Zjd");

int dev = 0;	// store the major dev number and the minor dev number

int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;	// major dev number
	int minor = CHRDEV_MINOR;		// minor dev number

	// dev = major << 20 | minor;
	// there is a define func to do this task
	dev = MKDEV(major, minor);

	register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of device

	return 0;
}

void __exit chrdev_exit(void)
{
	unregister_chrdev_region(dev, CHRDEV_NUM);

	return ;
}

module_init(chrdev_init);
module_exit(chrdev_exit);

4】编写Makefile

vim Makefile

obj-m += chrdev.o
KERNEL_PATH=/home/zjd/s5p6818/KERNEL/kernel
ROOTFS_PATH=/nfs_share/_install

all:
	make -C $(KERNEL_PATH) M=$(PWD) modules
	cp *.ko $(ROOTFS_PATH)

clean:
	make -C $(KERNEL_PATH) M=$(PWD) clean

5】编译工程

make

6】下位机验证

注意：我们现在只有设备号，而没有设备文件

【4】动态注册设备号

内核自己找一个没有注册的设备号，注册完归程序员使用

1】alloc_chrdev_region（注册设备号）

注释：

dev：回填设备号

baseminor：次设备号的基值（起始值）

count：要连续注册的设备号个数

name：给设备起的名称

2】unregister_chrdev_region（注销设备号）

注释：

from：要注销的起始设备号

count：要连续注销的设备号个数

【5】动态注册实验

1】编写程序

vim chrdev.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>

#define CHRDEV_MAGOR	200
#define CHRDEV_MINOR	10
#define CHRDEV_NUM		1
#define CHRDEV_NAME		"leds"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Zjd");

int dev = 0;	// store the major dev number and the minor dev number
#if 0
// fixed register
int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;	// major dev number
	int minor = CHRDEV_MINOR;		// minor dev number

	// dev = major << 20 | minor;
	// there is a define func to do this task
	dev = MKDEV(major, minor);

	register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of device

	return 0;
}
#else
// variable register
int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;	// major dev number
	int minor = CHRDEV_MINOR;		// minor dev number

	// there is a define func to register the number of devices automatically
	alloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);
	major = MAJOR(dev);	// gain the major dev number
	minor = MINOR(dev);	// gain the minor dev number
	
	printk(KERN_EMERG "dev number is :%d\n major number is :%d\n minor number is :%d\n", dev, major, minor);

	return 0;
}
#endif

void __exit chrdev_exit(void)
{
	unregister_chrdev_region(dev, CHRDEV_NUM);

	return ;
}

module_init(chrdev_init);
module_exit(chrdev_exit);

2】编写Makefile

vim Makefile

obj-m += chrdev.o
KERNEL_PATH=/home/zjd/s5p6818/KERNEL/kernel
ROOTFS_PATH=/nfs_share/_install

all:
	make -C $(KERNEL_PATH) M=$(PWD) modules
	cp *.ko $(ROOTFS_PATH)

clean:
	make -C $(KERNEL_PATH) M=$(PWD) clean

3】编译工程

make

4】下位机验证

注意：我们现在只有设备号，而没有设备文件

2）操作函数的集合

【1】操作函数集合

const struct file_operations *ops; // 操作函数的集合

实现一个字符设备驱动程序的主要编程工作都集中在操作函数集合，我们将来具体到某一个字符设备驱动程序的时候，只需要实现下列函数集合的子集就可以了。

【2】内核中提供的操作cdev的API

1】cdev_init（初始化cdev结构体）

2】cdev_add（将cdev注册到内核）

注释：

p：要注册的cdev地址

dev：要注册的设备号

count：要连续注册的cdev个数

3】cdev_del（从内核中注销cdev）

注释：

p：要注销的cdev地址

【3】实验

1】进入工程目录

cd /home/zjd/s5p6818/KERNEL/drivers

2】创建新的工程

mkdir chrdev_func

3】编写程序

vim chrdev_func.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>

#define CHRDEV_MAGOR	200
#define CHRDEV_MINOR	10
#define CHRDEV_NUM		1
#define CHRDEV_NAME		"myleds"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Zjd");

int dev = 0;	// store the major dev number and the minor dev number

// 1_step :define a struct cdev be named led_cdev
struct cdev led_cdev;

// 3_step :implement the function of led_fops
int led_open(struct inode *inode, struct file *fp)
{
	printk(KERN_EMERG "enter:%s\n", __FUNCTION__);

	return 0;
}

int led_close(struct inode *inode, struct file *fp)
{
	printk(KERN_EMERG "enter:%s\n", __FUNCTION__);

	return 0;
}

// 2_step :define a struct file_operation be named led_fops
// what functions shall we to implement ?
// there is turn_on and turn_off of the leds
// So, we should to implement the function of open() and release(), eithor or we should keep up the same type as the definations of the struct file_operations
struct file_operations led_fops = {
	.owner = THIS_MODULE,
	// int (*open) (struct inode *, struct file *);
	.open = led_open,
	// int (*release) (struct inode *, struct file *);
	.release = led_close
};

#if 0
// fixed register
int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;	// major dev number
	int minor = CHRDEV_MINOR;		// minor dev number

	// dev = major << 20 | minor;
	// there is a define func to do this task
	dev = MKDEV(major, minor);

	register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of device

	return 0;
}
#else
// variable register
int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;	// major dev number
	int minor = CHRDEV_MINOR;		// minor dev number

	// there is a define func to register the number of devices automatically
	alloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);
	major = MAJOR(dev);	// gain the major dev number
	minor = MINOR(dev);	// gain the minor dev number
	
	printk(KERN_EMERG "dev number is :%d\n major number is :%d\n minor number is :%d\n", dev, major, minor);

	// 4_step :initalize the struct cdev object led_cdev
	cdev_init(&led_cdev, &led_fops);

	// 5_step :register led_cdev into Kernel
	cdev_add(&led_cdev, dev, CHRDEV_NUM);

	return 0;
}
#endif

void __exit chrdev_exit(void)
{
	// 6_step :destory cdev
	cdev_del(&led_cdev);
	unregister_chrdev_region(dev, CHRDEV_NUM);

	return ;
}

module_init(chrdev_init);
module_exit(chrdev_exit);

4】编写Makefile

vim Makefile

obj-m += chrdev_func.o
KERNEL_PATH=/home/zjd/s5p6818/KERNEL/kernel
ROOTFS_PATH=/nfs_share/_install

all:
	make -C $(KERNEL_PATH) M=$(PWD) modules
	cp *.ko $(ROOTFS_PATH)

clean:
	make -C $(KERNEL_PATH) M=$(PWD) clean

5】编译工程

make

6】下位机安装模块

7】写一个应用层程序测试

mkdir test

cd test

vim led_test.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define CDEV_PATH	"/dev/myleds"

int main(void)
{
	int fd = 0;
	
	if((fd = open(CDEV_PATH, O_RDWR)) < 0) {
		perror("open()");
		return -1;
	}

	printf("open success!\n");

	sleep(5);

	printf("closing...\n");

	close(fd);

	return 0;
}

arm-cortex_a9-linux-gnueabi-gcc led_test.c -o led_test

cp led_test /nfs_share/_install/

8】下位机测试

手动创建设备文件

mknod /dev/myleds c 244 10

./led_test

9】疑惑

内核中的打印函数与应用程序中的打印函数，执行顺序孰先孰后？

不确定：内核打印输出的是自己维护的缓冲区，应用程序打印输出的是标准输出缓冲区

二、GPIO库

1、读懂开发板原理图

LED0 GPIOB26

LED1 GPIOC11

LED2 GPIOC7

LED3 GPIOC12

输出低电平，灯亮

输出高电平，灯灭

2、CPU Data Sheet

#define GPIOBOUT *(volatile unsigned int *)0xC001B000

#define GPIOBOUT *(volatile unsigned int *)0xC001B000

#define GPIOBOUT *(volatile unsigned int *)0xC001B000

#define GPIOBOUT *(volatile unsigned int *)0xC001B000

#define GPIOBOUT *(volatile unsigned int *)0xC001B000

#define GPIOBOUT *(volatile unsigned int *)0xC001B000

3、内核中提供的操作GPIO的API

【0】gpio宏定义

【1】gpio_request（申请GPIO管脚）

int gpio_request(unsigned gpio, const char *label)

【2】使用GPI管脚

1】gpio_direction_input（设置输入）

2】gpio_direction_output（设置输出）

3】gpio_set_value（设置value）

4】gpio_get_value（获取value）

【3】gpio_free（释放GPIO管脚）

void gpio_free(unsigned gpio)

4、实验

【1】进入工程目录

cd /home/zjd/s5p6818/KERNEL/drivers

【2】创建新的工程

mkdir led_drv

【3】编写程序

vim led_drv.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/gpio.h>
#include <mach/platform.h>

#define CHRDEV_MAGOR	200
#define CHRDEV_MINOR	26
#define CHRDEV_NUM		1
#define CHRDEV_NAME		"myleds"
#define HIGH			1
#define LOW				0

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Zjd");

int dev = 0;	// store the major dev number and the minor dev number

// 1_step :define a struct cdev be named led_cdev
struct cdev led_cdev;

// 3_step :implement the function of led_fops
int led_open(struct inode *inode, struct file *fp)
{
	printk(KERN_EMERG "enter:%s\n", __FUNCTION__);
	// c_step :set the value=0(turn on) of the gpio
	gpio_set_value(PAD_GPIOB26, LOW);

	return 0;
}

int led_close(struct inode *inode, struct file *fp)
{
	printk(KERN_EMERG "enter:%s\n", __FUNCTION__);
	// c_step :set the value=1(turn off) of the gpio
	gpio_set_value(PAD_GPIOB26, HIGH);

	return 0;
}

// 2_step :define a struct file_operation be named led_fops
// what functions shall we to implement ?
// there is turn_on and turn_off of the leds
// So, we should to implement the function of open() and release(), eithor or we should keep up the same type as the definations of the struct file_operations
struct file_operations led_fops = {
	.owner = THIS_MODULE,
	// int (*open) (struct inode *, struct file *);
	.open = led_open,
	// int (*release) (struct inode *, struct file *);
	.release = led_close
};

#if 0
// fixed register
int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;	// major dev number
	int minor = CHRDEV_MINOR;		// minor dev number

	// dev = major << 20 | minor;
	// there is a define func to do this task
	dev = MKDEV(major, minor);

	register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of device

	return 0;
}
#else
// variable register
int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;	// major dev number
	int minor = CHRDEV_MINOR;		// minor dev number

	// there is a define func to register the number of devices automatically
	alloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);
	major = MAJOR(dev);	// gain the major dev number
	minor = MINOR(dev);	// gain the minor dev number
	
	printk(KERN_EMERG "dev number is :%d\n major number is :%d\n minor number is :%d\n", dev, major, minor);

	// 4_step :initalize the struct cdev object led_cdev
	cdev_init(&led_cdev, &led_fops);

	// 5_step :register led_cdev into Kernel
	cdev_add(&led_cdev, dev, CHRDEV_NUM);

	// a_step :apply gpio
	gpio_request(PAD_GPIOB26, "LED0");

	// b_step :set the default value=1(turn_off) of GPIOB26
	gpio_direction_output(PAD_GPIOB26, HIGH);

	return 0;
}
#endif

void __exit chrdev_exit(void)
{
	// e_step :release gpio
	gpio_free(PAD_GPIOB26);

	// 6_step :destory cdev
	cdev_del(&led_cdev);
	unregister_chrdev_region(dev, CHRDEV_NUM);	// unregister the number of dev

	return ;
}

module_init(chrdev_init);
module_exit(chrdev_exit);

【4】编写Makefile

vim Makefile

obj-m += led_drv.o
KERNEL_PATH=/home/zjd/s5p6818/KERNEL/kernel
ROOTFS_PATH=/nfs_share/_install

all:
	make -C $(KERNEL_PATH) M=$(PWD) modules
	cp *.ko $(ROOTFS_PATH)

clean:
	make -C $(KERNEL_PATH) M=$(PWD) clean

【5】编译工程

make

【6】下位机安装模块

【7】编写应用层程序

mkdir test

cd test

vim led_test.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define CDEV_PATH	"/dev/myleds"

int main(void)
{
	int fd = 0;
	
	if((fd = open(CDEV_PATH, ORDWR)) < 0) {
		perror("open()");
		return -1;
	}

	printf("open success!\n");

	sleep(5);

	printf("closing...\n");

	close(fd);

	return 0;
}

arm-cortex_a9-linux-gnueabi-gcc led_test.c -o led_test

cp led_test /nfs_share/_install/

【8】下位机测试

手动创建设备文件

mknod /dev/myleds c 244 26

./led_test

三、用户态与内核态的数据交互

用户空间不能直接访问内核空间

内核空间不能直接访问用户空间

1）内核中提供的数据交互的API

【1】传递多数据

1】copy_to_user（内核到用户）

int copy_to_user(void __user *to, const void *from, int n)

注释：

to：内核空间缓冲区地址，

from：用户空间地址

n：数据字节数

retval：不能被复制的字节数，返回0表示全部复制成功。

2】copy_from_user（用户到内核）

int copy_from_user(void *to, const void __user *from, int n)

注释：

to：内核空间缓冲区地址，

from：用户空间地址

n：数据字节数

retval：不能被复制的字节数，返回0表示全部复制成功。

【2】传递单数据

可以从指定空间获取单个数据，单个数据并不是指一个字节数据，对ARM而言，一次性可获取一个char、short或者 int型的数据，即1、2或者4字节。

1】put_user(x, ptr)（内核到用户）

注释：

x ：内核空间的数据，

p ：用户空间的指针。

传递成功，返回 0，否则返回-EFAULT。

2】get_user(x, ptr)（用户到内核）

注释：

x ：内核空间的数据，

p ：用户空间的指针。

传递成功，返回 0，否则返回-EFAULT。

注意：

以上API与C标准库中memcpy(3)相似，但多了一个对访问的空间的权限检查

2、实验

【1】进入工程目录

cd /home/zjd/s5p6818/KERNEL/drivers

【2】创建新的工程

mkdir param_drv

【3】编写程序

vim param_drv.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/gpio.h>
#include <mach/platform.h>
#include <linux/uaccess.h>

#define CHRDEV_MAGOR	200
#define CHRDEV_MINOR	26
#define CHRDEV_NUM		1
#define CHRDEV_NAME		"myleds"
#define HIGH			1
#define LOW				0
#define LED0	(PAD_GPIO_B + 26)
#define LED1	(PAD_GPIO_C + 12)
#define LED2	(PAD_GPIO_C + 7)
#define LED3	(PAD_GPIO_C + 11)

unsigned int leds[] = {LED0, LED1, LED2, LED3};
const char *leds_label[] = {"LED0", "LED1", "LED2", "LED3"};

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Zjd");

int dev = 0;

struct cdev led_cdev;

int k_cmd = 0;	//kernel's buffer
int k_status = 0;	//the state of LEDs

int led_open(struct inode *inode, struct file *fp)
{
	return 0;
}

int led_close(struct inode *indoe, struct file *fp)
{
	return 0;
}

ssize_t led_read(struct file *fp, char __user *buf, size_t len, loff_t *offset)
{
	int ret = 0;

	ret = copy_to_user(buf, &k_status, len);

	return len;
}

ssize_t led_write(struct file *fp, const char __user *buf, size_t len, loff_t *offset)
{
	int ret = 0;
	int i = 0;

	ret = copy_from_user(&k_cmd, buf, len);

	for (i = 0; i < sizeof(leds) / sizeof(leds[0]); i++) {
		gpio_set_value(leds[i], k_cmd);
	}
	k_status = k_cmd;

	return len;
}

struct file_operations led_fops = {
	.owner = THIS_MODULE,
	.open = led_open,
	.release = led_close,
	.read = led_read,
	.write = led_write
};

int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;
	int minor = CHRDEV_MINOR;
	int i = 0;

	alloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);
	major = MAJOR(dev);
	minor = MINOR(dev);

	printk(KERN_EMERG "major = %d\nminor = %d\n", major, minor);

	cdev_init(&led_cdev, &led_fops);

	cdev_add(&led_cdev, dev, CHRDEV_NUM);

	for (i = 0; i < sizeof(leds) / sizeof(leds[0]); i++) {
		gpio_request(leds[i], leds_label[i]);
		gpio_direction_output(leds[i], HIGH);
	}

	return 0;
}

void __exit chrdev_exit(void)
{
	int i = 0;

	for (i = 0; i < sizeof(leds) / sizeof(leds[0]); i++) {
		gpio_free(LED1);
	}

	cdev_del(&led_cdev);
	unregister_chrdev_region(dev, CHRDEV_NUM);

	return ;
}

module_init(chrdev_init);
module_exit(chrdev_exit);

【4】编写Makefile

vim Makefile

obj-m += param_drv.o
KERNEL_PATH=/home/zjd/s5p6818/KERNEL/kernel
ROOTFS_PATH=/nfs_share/_install

all:
	make -C $(KERNEL_PATH) M=$(PWD) modules
	cp *.ko $(ROOTFS_PATH)

clean:
	make -C $(KERNEL_PATH) M=$(PWD) clean

【5】编译工程

make

【6】下位机安装模块

【7】编写应用层程序

mkdir test

cd test

vim led_test.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

#define ON		0
#define OFF		1
#define CDEV_PATH	"/dev/myleds"

int main(int argc, char *argv[])
{
	int fd = 0;
	int cmd = 0;
	int status = 0;

	if (argc < 2) {
		printf("Usage : %s <on/off>\n", argv[0]);
		return -1;
	}

	if (!strcmp(argv[1], "on")) {
		cmd = ON;
	} else if (!strcmp(argv[1], "off")){
		cmd = OFF;
	} else {
		printf("illegal param\n");
		return -2;
	}
	
	if((fd = open(CDEV_PATH, O_RDWR)) < 0) {
		perror("open()");
		return -3;
	}

	printf("open success!\n");

	write(fd, &cmd, sizeof(cmd));
	read(fd, &status, sizeof(status));

	if (status == ON) {
		printf("Led is On!\n");
	} else {
		printf("Led is Off!\n");
	}

	printf("closing...\n");

	close(fd);

	return 0;
}

vim Makefile

SRC=led_test.c
OBJ=led_test

ARM_COMPILE=arm-cortex_a9-linux-gnueabi-
GCC=gcc

ROOTFS_PATH=/nfs_share/_install

all:
	$(ARM_COMPILE)$(GCC) $(SRC) -o $(OBJ)
	cp $(OBJ) $(ROOTFS_PATH)

clean:
	rm -rf $(OBJ)

【8】编译工程

make

【9】下位机测试

手动创建设备文件

mknod /dev/myleds c 244 26

./led_test

四、ioctl

1）介绍

2）实操

【1】进入工程目录

cd /home/zjd/s5p6818/KERNEL/drivers

【2】创建新的工程

mkdir ioctl

【3】编写程序

vim ioctl.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/gpio.h>
#include <mach/platform.h>
#include <linux/uaccess.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Zjd");

#define CHRDEV_MAGOR	200
#define CHRDEV_MINOR	26
#define CHRDEV_NUM		1
#define CHRDEV_NAME		"myleds"
#define HIGH			1
#define LOW				0
#define LED0	(PAD_GPIO_B + 26)
#define LED1	(PAD_GPIO_C + 12)
#define LED2	(PAD_GPIO_C + 7)
#define LED3	(PAD_GPIO_C + 11)
#define TURN_ON			LOW
#define TURN_OFF		HIGH



dev_t dev = 0;

struct cdev led_cdev;

typedef struct led_desc{
	unsigned int gpio;
	char *name;
}led_desc_t;

led_desc_t leds[] = {
	{LED0, "LED0"},
	{LED1, "LED1"},
	{LED2, "LED2"},
	{LED3, "LED3"}
};

long led_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
{
	int k_index = 0;
	int ret = 0;

	ret = copy_from_user(&k_index, (const void *)arg, sizeof(int));
	if (k_index > 4 || k_index < 1)
		return -EINVAL;
	
	switch (cmd) {
		case TURN_ON:
			gpio_set_value(leds[k_index - 1].gpio, LOW);
			break;
		case TURN_OFF:
			gpio_set_value(leds[k_index - 1].gpio, HIGH);
			break;
		default:
			return -EINVAL;
	}

	return arg;
}

struct file_operations led_fops = {
	.owner = THIS_MODULE,
	.unlocked_ioctl = led_ioctl
};

int __init chrdev_init(void)
{
	int major = CHRDEV_MAGOR;
	int minor = CHRDEV_MINOR;
	int i = 0;

	alloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);
	major = MAJOR(dev);
	minor = MINOR(dev);

	printk(KERN_EMERG "major = %d\nminor = %d\n", major, minor);

	cdev_init(&led_cdev, &led_fops);

	cdev_add(&led_cdev, dev, CHRDEV_NUM);

	for (i = 0; i < ARRAY_SIZE(leds); i++) {
		gpio_request(leds[i].gpio, leds[i].name);
		gpio_direction_output(leds[i].gpio, HIGH);
	}

	return 0;
}

void __exit chrdev_exit(void)
{
	int i = 0;

	for (i = 0; i < ARRAY_SIZE(leds); i++) {
		gpio_free(leds[i].gpio);
	}

	cdev_del(&led_cdev);
	unregister_chrdev_region(dev, CHRDEV_NUM);

	return ;
}

module_init(chrdev_init);
module_exit(chrdev_exit);

【4】编写Makefile

vim Makefile

obj-m += ioctl.o
KERNEL_PATH=/home/zjd/s5p6818/KERNEL/kernel
ROOTFS_PATH=/nfs_share/_install

all:
	make -C $(KERNEL_PATH) M=$(PWD) modules
	cp *.ko $(ROOTFS_PATH)

clean:
	make -C $(KERNEL_PATH) M=$(PWD) clean

【5】编译工程

make

【6】下位机安装模块

【7】编写应用层程序

mkdir test

cd test

vim led_test.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <stdlib.h>

#define ON		0
#define OFF		1
#define CDEV_PATH	"/dev/myleds"

int main(int argc, char *argv[])
{
	int fd = 0;
	int cmd = 0;
	int index = 0;

	if (argc < 3) {
		printf("Usage : %s <on/off> <1/2/3/4>\n", argv[0]);
		return -1;
	}

	if (!strcmp(argv[1], "on")) {
		cmd = ON;
	} else if (!strcmp(argv[1], "off")){
		cmd = OFF;
	} else {
		printf("illegal param\n");
		return -2;
	}
	
	index = atoi(argv[2]);
	if (index < 1 || index > 4) {
		printf("illegal param\n");
		return -2;
	}

	if((fd = open(CDEV_PATH, O_RDWR)) < 0) {
		perror("open()");
		return -3;
	}
	printf("open success!\n");

	ioctl(fd, cmd, &index);

	printf("closing...\n");

	close(fd);

	return 0;
}

vim Makefile

SRC=led_test.c
OBJ=led_test

ARM_COMPILE=arm-cortex_a9-linux-gnueabi-
GCC=gcc

ROOTFS_PATH=/nfs_share/_install

all:
	$(ARM_COMPILE)$(GCC) $(SRC) -o $(OBJ)
	cp $(OBJ) $(ROOTFS_PATH)

clean:
	rm -rf $(OBJ)

【8】编译工程

make

【9】下位机测试

手动创建设备文件

mknod /dev/myleds c 244 26

./led_test