将自己开发的内核代码加入到Linux内核中,需要3个步骤:
1、确定把自己开发代码放入到内核合适的位置
将demo_chardev.c文件拷贝到.../drivers/char/目录下。
demo_chardev.c
- #include <linux/init.h>
- #include <linux/module.h>
- #include <linux/kernel.h>
- /*结构体file_operations定义的头文件*/
- #include <linux/fs.h>
- /*声明copy_to/from_user函数的头文件*/
- #include <linux/uaccess.h>
- /*声明class_create 和device_create相关信息*/
- #include <linux/device.h>
- #define DEMO_DEBUG
- #ifdef DEMO_DEBUG
- #define dem_dbg(fmt, arg...) printk(KERN_WARNING fmt, ##arg)
- #else
- #define dem_dbg(fmt, arg...) printk(KERN_DEBUG fmt, ##arg)
- #endif
- #define DEVICE_COUNT 2
- /*记录当前驱动所占用的主设备号*/
- static int major = 0;
- static int demo_open (struct inode *pnode, struct file *filp)
- {
- dem_dbg("[kern func]: %s major: %d minor: %d ",
- __FUNCTION__, imajor(pnode), iminor(pnode));
- return 0;
- }
- static ssize_t demo_read (struct file *filp, char __user *buf, size_t count, loff_t *offp)
- {
- unsigned char ary[100] = "you are reading successfully!";
- unsigned long len = min(count, sizeof(ary)); //min是个宏,用来获取两个数中较小的值
- int retval;
- dem_dbg("[kern func]: %s major: %d minor: %d ",
- __FUNCTION__, imajor(filp->f_dentry->d_inode),
- iminor(filp->f_dentry->d_inode));
- //file结构体的f_flags成员可用来判断是否阻塞读取,然后进行相应处理
- if(copy_to_user(buf, ary, len) != 0){
- retval = -EFAULT;
- goto cp_err;
- }
- return len; //成功返回实际传输的字节数
- cp_err:
- return retval;
- }
- static ssize_t demo_write(struct file *filp, const char __user *buf, size_t count, loff_t *offp)
- {
- unsigned char ary[100] = "";
- unsigned long len = min(count, sizeof(ary)); //min是个宏,用来获取两个数中较小的值
- int retval;
- dem_dbg("[kern func]: %s major: %d minor: %d ",
- __FUNCTION__, imajor(filp->f_dentry->d_inode),
- iminor(filp->f_dentry->d_inode));
- if(copy_from_user(ary, buf, len) != 0){
- retval = -EFAULT;
- goto cp_err;
- }
- printk("[msg]: writing context: %s ",ary);
- return len; //成功返回实际传输的字节数
- cp_err:
- return retval;
- }
- static int demo_release (struct inode *pnode, struct file *filp)
- {
- dem_dbg("[kern func]: %s major: %d minor: %d ",
- __FUNCTION__, imajor(pnode), iminor(pnode));
- return 0;
- }
- /*@定义file_operations结构体变量*/
- static struct file_operations fops = {
- .owner = THIS_MODULE,
- .read = demo_read,
- .write = demo_write,
- .open = demo_open,
- .release = demo_release,
- };
- static struct class *demo_class;
- static int __init drvdemo_init(void)
- {
- struct device *demo_device;
- int i;
- int retval;
- dem_dbg("[msg]:this is a driver demo, in module initial function ");
- /*注册字符驱动函数,成功 返回动态分配好的主设备号,失败
- *返回错误码(负值)*/
- major = register_chrdev(0, "demo_chrdev", &fops);
- if(major < 0){
- retval = major;
- goto chrdev_err;
- }
- /*创建设备类*/
- demo_class = class_create(THIS_MODULE,"demo_class");
- if(IS_ERR(demo_class)){
- retval = PTR_ERR(demo_class);
- goto class_err;
- }
- /*创建设备文件,通知用户在“/dev/”目录下创件名字为demoX的设备文件*/
- for(i=0; i<DEVICE_COUNT; i++){ //最多可创建255个设备节点(register_chrdev函数会申请0-254范围的从设备号)
- demo_device = device_create(demo_class,NULL, MKDEV(major, i), NULL,"demo%d",i);
- if(IS_ERR(demo_device)){
- retval = PTR_ERR(demo_device);
- goto device_err;
- }
- }
- return 0;
- device_err:
- while(i--) //设备节点创建的回滚操作 device_destroy(demo_class,MKDEV(major, i));
- class_destroy(demo_class); //删除设备类
- class_err:
- unregister_chrdev(major, "demo_chrdev");
- chrdev_err:
- return retval;
- }
- static void __exit drvdemo_exit(void)
- {
- int i;
- dem_dbg("[msg]:in module exit function ");
- /*注销字符驱动函数,无返回值,major为已分配的主设备号*/
- unregister_chrdev(major, "demo_chrdev");
- /*删除设备节点和设备类*/
- for(i=0; i<DEVICE_COUNT; i++)
- device_destroy(demo_class,MKDEV(major, i));
- class_destroy(demo_class);
- }
- module_init(drvdemo_init);
- module_exit(drvdemo_exit);
- MODULE_LICENSE("Dual BSD/GPL"); //BSD/GPL双重许可证
- MODULE_AUTHOR("hanbo"); //模块作者(可选)
- MODULE_DESCRIPTION("used for studing linux drivers"); //模块儿简介(可选)
2、把自己开发的功能增加到Linux内核的配置选项中,使用户能够选择此功能
vi drivers/char/Konfig 在文件结尾,endmenu的前面加入一个config选项
- config DEMO_CHARDEV
- bool "demo_chardev driver for hanbo chardev boards"
- default y
- help
- this is CHARDEV driver for hanbo chardev boards.
3、构建或修改Makefile,根据用户的选择,将相应的代码编译到最终生成的Linux内核中去
make menuconfig(添加配置选项)(如果提示找不到“ncurses”库则执行命令: sudo apt-get install libncurses5-dev )
Device driver -->
character devices ->
[*] demo_chardev driver for hanbo chardev boards
4、vi drivers/char/Makefile 添加内容如下:
..........
obj-$(CONFIG_DEMO_CHARDEV) +=demo_chardev.o (添加)
obj-$(CONFIG_JS_RTC) +=js-rtc.o(自带)
js-rtc-y = rtc.o (自带)
5、make (更新内核镜像到开发板)
6、交叉编译测试程序,放到开发板运行
arm-linux-gcc-gcc test.c -o demo
test.c
- #include <stdio.h>
- #include <stdlib.h>
- #include <unistd.h>
- #include <fcntl.h>
- #include <string.h>
- int main(int argc, char *argv[])
- {
- int fd1 = 0, fd2 = 0;
- unsigned char buf1[100] = "I am a test program!";
- unsigned char buf2[100] = {0};
- int retval;
- //以读写、不阻塞方式打开设备文件
- fd1 = open("/dev/demo0", O_RDWR | O_NONBLOCK);
- if(fd1 < 0){
- perror("open /dev/demo1");
- goto out;
- }
- //以只读、阻塞方式打开设备文件
- fd2 = open("/dev/demo1", O_RDONLY);
- if(fd2 < 0){
- perror("open /dev/demo2");
- goto out;
- }
- //成功返回实际写入字节数,失败返回负值
- retval = write(fd1, buf1, strlen(buf1)+1);
- if(retval < 0){
- perror("writing fd1 failed!");
- goto out;
- }
- printf("<user space>: write bytes: %d write content: %s ", retval, buf1);
- //成功返回实际读取字节数,失败返回负值
- retval = read(fd2, buf2, sizeof(buf2));
- if(retval < 0){
- perror("reading fd2 failed!");
- goto out;
- }
- printf("<user space>: read bytes: %d read content: %s ", retval, buf2);
- return 0;
- out:
- if(fd1 > 0)
- close(fd1);
- if(fd2 > 0)
- close(fd2);
- return -1;
- }
二、手动加载驱动 .ko文件
1、上面的demo_chardev.c文件放到内核下编译生成 .ko文件
Makefile
- #如果已定义KERNELRELEASE,说明是由内核构造系统调用的
- #可以利用内建语句
- ifneq ($(KERNELRELEASE),)
- obj-m +=demo_chrdev.o
- #此时由内核构造系统调用
- else
- #定义并记录内核源码路径
- KERNELDIR = /home/hanbo/linux-2.6.35.7(自己源码路径,2.6.35.7指当前内核版本)
- #记录当前工程目录
- PWD := $(shell pwd)
- default:
- $(MAKE) -C $(KERNELDIR) M=$(PWD) modules
- @rm -rf *.o .t* .m* .*.cmd *.mod.c *.order *.symvers
- endif
- clean:
- rm -rf *.ko *.o .t* .m* .*.cmd *.mod.c *.order *.symvers
2、 然后用命令加载 .ko 驱动
lsmod 列举当前系统中的所有模块
lsmod 列举当前系统中的所有模块
rmmod xxx 卸载指定模块(不需要.ko后缀)
3、如果自己编译的代码中没有用
/*创建设备类*/
demo_class = class_create(THIS_MODULE,"demo_class");
/*创建设备文件,通知用户在“/dev/”目录下创件名字为demoX的设备文件*/
demo_device = device_create(demo_class,NULL, MKDEV(major, i), NULL,"demo%d",i);
则需要手动添加设备节点
mknod /dev/demo1 c 主设备号 0
mknod /dev/demo2 c 主设备号 1
注意:若卸载时出现提示 rmmod:chdir(2.6.35.7):No such file or directory
则在开发板根文件系统下创建目录:/lib/modules/2.6.35.7(跟当前内核版本同名)