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前言
创建一个简单的字符设备驱动程序。
本文命令的运行基本上都需要root权限,使用root账号,或者在命令前面加上sudo。
如果你使用ssh远程连接的服务器进行代码编写。那么不要在root用户下创建文件或者文件夹。这会导致你ssh连接vscode编写代码的权限问题。可以在普通用户创建好所有的文件,然后编写。
代码
驱动程序
hello_driver.c- #include <linux/types.h>
- #include <linux/init.h>
- #include <linux/interrupt.h>
- #include <linux/mm.h>
- #include <linux/slab.h>
- #include <linux/spinlock.h>
- #include <linux/module.h>
- #include <linux/device.h>
- #include <linux/cdev.h>
-
-
- dev_t hello_devid;
- struct cdev hello_cdev;
- int hello_major = 0;
- int hello_minor;
-
-
- uint8_t kernel_buffer[1024] = {0};
- static struct class *hello_class;
-
-
-
- static int hello_world_open(struct inode * inode, struct file * file)
- {
- printk("hello_world_open\r\n");
- return 0;
- }
-
- static int hello_world_release (struct inode * inode, struct file * file)
- {
- printk("hello_world_release\r\n");
- return 0;
- }
-
- static ssize_t hello_world_read (struct file * file, char __user * buffer, size_t size, loff_t * ppos)
- {
- printk("hello_world_read size:%ld\r\n",size);
- copy_to_user(buffer,kernel_buffer,size);
- return size;
- }
-
- static ssize_t hello_world_write(struct file * file, const char __user * buffer, size_t size, loff_t *ppos)
- {
- printk("hello_world_write size:%ld\r\n",size);
- copy_from_user(kernel_buffer,buffer,size);
- return size;
- }
-
-
- static const struct file_operations hello_world_fops = {
- .owner = THIS_MODULE,
- .open = hello_world_open,
- .release = hello_world_release,
- .read = hello_world_read,
- .write = hello_world_write,
- };
-
-
- static int __init hello_driver_init(void)
- {
- int ret;
- printk("hello_driver_init\r\n");
-
- alloc_chrdev_region(&hello_devid, 0, 1, "hello");
- hello_major = MAJOR(hello_devid);
- hello_minor = MINOR(hello_devid);
- printk("hello driver major=%d,minor=%d\r\n",hello_major, hello_minor);
-
- hello_cdev.owner = THIS_MODULE;
- cdev_init(&hello_cdev, &hello_world_fops);
- cdev_add(&hello_cdev, hello_devid, 1);
-
- hello_class = class_create(THIS_MODULE,"hello_class");
-
- device_create(hello_class,NULL,hello_devid,NULL,"hello"); /* /dev/hello */
-
- return 0;
- }
-
- static void __exit hello_driver_cleanup(void)
- {
- printk("hello_driver_cleanup\r\n");
- cdev_del(&hello_cdev);
- unregister_chrdev_region(hello_devid, 1);
-
- device_destroy(hello_class,hello_devid);
- class_destroy(hello_class);
-
- }
-
-
- module_init(hello_driver_init);
- module_exit(hello_driver_cleanup);
- MODULE_LICENSE("GPL");
复制代码 Makefile文件
- KERNELDIR := /lib/modules/$(shell uname -r)/build
- CURRENT_PATH := $(shell pwd)
- obj-m := hello_driver.o
- KBUILD_CFLAGS += -Wno-unused-result -Wno-unused-variable
- build: kernel_modules
-
- kernel_modules:
- $(MAKE) ${CFLAGS} -C $(KERNELDIR) M=$(CURRENT_PATH) modules
- $(CROSS_COMPILE)gcc -o test_app test_app.c
- clean:
- $(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) clean
- rm -rf test_app
复制代码 测试程序
test_app.c- #include <stdio.h>
- #include <unistd.h>
- #include <sys/types.h>
- #include <sys/stat.h>
- #include <fcntl.h>
- #include <stdlib.h>
- #include <string.h>
- #include <stdint.h>
- uint8_t buffer[512] = {0};
-
- int main(int argc, char *argv[])
- {
- int fd;
- int ret;
-
- fd = open(argv[1], O_RDWR);
- if(!fd)
- {
- printf("everthing is error\n");
- }
-
- if(!strcmp("read",argv[2]))
- {
- printf("read data from kernel\r\n");
- ret = read(fd,buffer,sizeof(buffer));
- printf("ret len:%d data:%s\r\n",ret,buffer);
- }
-
- if(!strcmp("write",argv[2]))
- {
- printf("write data to kernel %s len:%ld\r\n",argv[3],strlen(argv[3]));
- ret = write(fd,argv[3],strlen(argv[3]));
- printf("ret len:%d\r\n",ret);
- }
-
-
- close(fd);
-
-
- }
复制代码 编译
执行make命令编译- root@ubuntu:/home/dong/workspace/drivercode# make
- make -C /lib/modules/5.19.0-38-generic/build M=/home/dong/workspace/drivercode modules
- make[1]: Entering directory '/usr/src/linux-headers-5.19.0-38-generic'
- warning: the compiler differs from the one used to build the kernel
- The kernel was built by: x86_64-linux-gnu-gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
- You are using: gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
- CC [M] /home/dong/workspace/drivercode/hello_driver.o
- MODPOST /home/dong/workspace/drivercode/Module.symvers
- CC [M] /home/dong/workspace/drivercode/hello_driver.mod.o
- LD [M] /home/dong/workspace/drivercode/hello_driver.ko
- BTF [M] /home/dong/workspace/drivercode/hello_driver.ko
- Skipping BTF generation for /home/dong/workspace/drivercode/hello_driver.ko due to unavailability of vmlinux
- make[1]: Leaving directory '/usr/src/linux-headers-5.19.0-38-generic'
- gcc -o test_app test_app.c
复制代码 会生成hello_driver.ko文件和test_app
加载模块
insmod hello_driver.ko
卸载模块
rmmod hello_driver
查看模块
lsmod |grep hello_driver
运行测试
创建设备文件
这个文件不是随便创造的,会分配设备号,如果不使用分配的设备号创建会出现读写错误。
每一次加载或者卸载模块都会有dmesg信息。
使用dmesg -c清除信息。加载模块,使用dmesg查看模块信息。- root@ubuntu:/home/dong/workspace/drivercode# dmesg
- [164284.337396] hello_driver_init
- [164284.337399] hello driver major=238,minor=0
复制代码 我的设备主设备号就是238,从设备号是0
创建设备文件命令
mknod /dev/hello c 238 0
测试
读 : ./test_app /dev/hello read
写: ./test_app /dev/hello write 需要写入的内容
来源:https://www.cnblogs.com/wdgray/p/17337041.html
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