wordpress标题怎么写长沙seo霜天
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) clean5】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) clean3】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) clean5】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
