正规网站有哪些,网站建设计算机人员招聘,高权重网站出售,徐州网架公司一、字符设备的编程框架 在Linux_kernel驱动开发11中#xff0c;我们介绍的系统调用。只是为了做一个实验#xff0c;在真正开发时#xff0c;我们并不会直接在内核中添加一个新的系统调用#xff0c;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…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 ledsMODULE_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 ledsMODULE_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 myledsMODULE_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/myledsint 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 value0(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 value1(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 value1(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/myledsint 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; //kernels 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/myledsint 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 SRCled_test.c
OBJled_testARM_COMPILEarm-cortex_a9-linux-gnueabi-
GCCgccROOTFS_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.hMODULE_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/myledsint 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 SRCled_test.c
OBJled_testARM_COMPILEarm-cortex_a9-linux-gnueabi-
GCCgccROOTFS_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
