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 numberint __init chrdev_init(void)
{int major = CHRDEV_MAGOR;	// major dev numberint minor = CHRDEV_MINOR;		// minor dev number// dev = major << 20 | minor;// there is a define func to do this taskdev = MKDEV(major, minor);register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of devicereturn 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/_installall:make -C $(KERNEL_PATH) M=$(PWD) modulescp *.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 numberint minor = CHRDEV_MINOR;		// minor dev number// dev = major << 20 | minor;// there is a define func to do this taskdev = MKDEV(major, minor);register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of devicereturn 0;
}
#else
// variable register
int __init chrdev_init(void)
{int major = CHRDEV_MAGOR;	// major dev numberint minor = CHRDEV_MINOR;		// minor dev number// there is a define func to register the number of devices automaticallyalloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);major = MAJOR(dev);	// gain the major dev numberminor = MINOR(dev);	// gain the minor dev numberprintk(KERN_EMERG "dev number is :%d\n major number is :%d\n minor number is :%d\n", dev, major, minor);return 0;
}
#endifvoid __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/_installall:make -C $(KERNEL_PATH) M=$(PWD) modulescp *.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 numberint minor = CHRDEV_MINOR;		// minor dev number// dev = major << 20 | minor;// there is a define func to do this taskdev = MKDEV(major, minor);register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of devicereturn 0;
}
#else
// variable register
int __init chrdev_init(void)
{int major = CHRDEV_MAGOR;	// major dev numberint minor = CHRDEV_MINOR;		// minor dev number// there is a define func to register the number of devices automaticallyalloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);major = MAJOR(dev);	// gain the major dev numberminor = MINOR(dev);	// gain the minor dev numberprintk(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_cdevcdev_init(&led_cdev, &led_fops);// 5_step :register led_cdev into Kernelcdev_add(&led_cdev, dev, CHRDEV_NUM);return 0;
}
#endifvoid __exit chrdev_exit(void)
{// 6_step :destory cdevcdev_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/_installall:make -C $(KERNEL_PATH) M=$(PWD) modulescp *.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				0MODULE_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 gpiogpio_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 gpiogpio_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 numberint minor = CHRDEV_MINOR;		// minor dev number// dev = major << 20 | minor;// there is a define func to do this taskdev = MKDEV(major, minor);register_chrdev_region(dev, CHRDEV_NUM, CHRDEV_NAME);	//register the number of devicereturn 0;
}
#else
// variable register
int __init chrdev_init(void)
{int major = CHRDEV_MAGOR;	// major dev numberint minor = CHRDEV_MINOR;		// minor dev number// there is a define func to register the number of devices automaticallyalloc_chrdev_region(&dev, CHRDEV_MINOR, CHRDEV_NUM, CHRDEV_NAME);major = MAJOR(dev);	// gain the major dev numberminor = MINOR(dev);	// gain the minor dev numberprintk(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_cdevcdev_init(&led_cdev, &led_fops);// 5_step :register led_cdev into Kernelcdev_add(&led_cdev, dev, CHRDEV_NUM);// a_step :apply gpiogpio_request(PAD_GPIOB26, "LED0");// b_step :set the default value=1(turn_off) of GPIOB26gpio_direction_output(PAD_GPIOB26, HIGH);return 0;
}
#endifvoid __exit chrdev_exit(void)
{// e_step :release gpiogpio_free(PAD_GPIOB26);// 6_step :destory cdevcdev_del(&led_cdev);unregister_chrdev_region(dev, CHRDEV_NUM);	// unregister the number of devreturn ;
}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/_installall:make -C $(KERNEL_PATH) M=$(PWD) modulescp *.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 LEDsint 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/_installall:make -C $(KERNEL_PATH) M=$(PWD) modulescp *.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_testARM_COMPILE=arm-cortex_a9-linux-gnueabi-
GCC=gccROOTFS_PATH=/nfs_share/_installall:$(ARM_COMPILE)$(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		HIGHdev_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/_installall:make -C $(KERNEL_PATH) M=$(PWD) modulescp *.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_testARM_COMPILE=arm-cortex_a9-linux-gnueabi-
GCC=gccROOTFS_PATH=/nfs_share/_installall:$(ARM_COMPILE)$(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