驱动程序(简易字符驱动程序）

1、编写驱动程序

///char.c
# ifndef __KERNEL__
# define __KERNEL__
# endif
# ifndef MODULE
# define MODULE
# endif
# include <linux/mm.h>
#include <linux/module.h>
#include <asm/segment.h>
#include <asm/uaccess.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/proc_fs.h>
#include <linux/fcntl.h>
#include <asm/switch_to.h>  //3.3 之后替换了 #include <asm/system.h>
#define DEVICE_NAME "demodrv"
#define demo_MAJOR 267
#define demo_MINOR 0
static int MAX_BUF_LEN = 1024;
static char drv_buf[1024];
static int WRI_LENGTH =0;
static ssize_t demo_write(struct file *,const char *,size_t,loff_t *);
static ssize_t demo_read(struct file *,char *,size_t,loff_t *);
static struct file_operations demo_fops=
{
        owner:THIS_MODULE,
        //open:demo_open
        read:demo_read,
        write:demo_write,
        //llseek:demo_llseek(),
        //ioctl:demo_ioctl,
        //release:demo_release,
};
static void do_write(void)
{
        int i;
        int len = WRI_LENGTH;
        char tmp;
        for(i = 0;i<(len>>1);i++,len--)
        {
                tmp = drv_buf[len--];
                drv_buf[len-1] = drv_buf[i];
                drv_buf[i] = tmp;
        }
}
static ssize_t demo_read(struct file *filp,char *buffer,size_t count,loff_t *ppos)
{
        if(count>MAX_BUF_LEN)
                count = MAX_BUF_LEN;
        //copy_to_user(buffer,drv_buf,count);
        printk("user read data from driver\n");
        return (ssize_t)count;
}
static ssize_t demo_write(struct file *filp,const char *buffer,size_t count,loff_t *ppos)
{
        if(count>MAX_BUF_LEN)
                count = MAX_BUF_LEN;
        WRI_LENGTH = count;
        printk("user write data to driver\n");
        do_write();
        return (ssize_t)count;
}
static int __init demo_init(void)
{
        int result;
        result = register_chrdev(demo_MAJOR,"char",&demo_fops);
        if(result<0)
        {
                printk(DEVICE_NAME"initialized failure\n");
                return result;
        }
        else
        {
                printk(DEVICE_NAME"initialized!\n");
                return 0;
        }
}
static void __exit demo_exit(void)
{
        //unregister_chrdev(demo_MAJOR,"demodrv");
        kfree(demo_devices);
        printk(DEVICE_NAME"unloaded\n");
}

2、编写Makefile

ifneq ($(KERNELRELEASE),)
#MODULE_NAME= demodrv
#$(MODULE_NAME)-objs:= char.o

obj-m:= char.o
else
KERNEL_DIR = /lib/modules/$(shell uname -r)/build
MODULEDIR:= $(shell pwd)

.PHONY: modules
default: modules
modules:
        make -C $(KERNEL_DIR) M=$(MODULEDIR) modules
clean distclean:
        rm -f *.o *.mod.c .*.*.cmd * .ko.Mod*.* mo*.*
        rm-f .tmp_versions
endif

3、测设驱动模块的应用程序

//test_demo.c
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<unistd.h>
#include<sys/ioctl.h>
void showbuf(char *buf);
int MAX_LEN = 32;
int main()
{
        int fd;
        int i;
        char buf[255];
        for(i=0;i<MAX_LEN;i++)
        {
                buf[i]=i;
        }
        fd = open("/dev/chardrv",O_RDWR);
        if(fd<0)
        {
                printf("# # # DEMO device open fail####\n");
                return (-1);
        }
        printf("write %d bytes date to /dev/demo\n",MAX_LEN);
        showbuf(buf);
        write(fd,buf,MAX_LEN);
        printf("Read %d bytes date from /dev/demo \n",MAX_LEN);
        read(fd,buf,MAX_LEN);
        showbuf(buf);
        ioctl(fd,1,NULL);
        ioctl(fd,4,NULL);
        close(fd);
        return 0;
}
void showbuf(char * buf)
{
        int i,j=0;
        for(i=0;i<MAX_LEN;i++)
        {
                if(i%4==0)
                {
                        printf("\n%4d:",j++);
                        printf("%4d",buf[i]);
                }
                printf("\n#############################\n");
        }
}

4、使用make编译驱动和测试文件&&生成.ko和test_demo可执行文件

成功生成.ko。
nice!!!
--------------------------------------------------------------------------

5、创建设备节点使用mknod命令

mknod /dev/chardrv c 277 0

• cat /proc/devices 命令。查看主设备号，看是否已经存在自己想创建的设备号（demo_MAJOR）。
• 删除节点 rm -f /dev/chardrv

6、插入驱动模块 insmod char.ko

lsmod查看

7、测试 ./test_demo

8、问题

碰到一个解决一个，这个过程才是收获最大的。老师说，这可比你做题有益多的多。

continuing