正文
Linux符设备驱动编程
提示：扫一扫查出行【扫一扫了解最新限行尾号】
复制提示
加入内核源码树外
① 建立两个文件scull.c，scull.h，以及Makefile文件
Makefile文件
② 用make进行编译，生成scull.ko驱动程序模块
③ 把scull.ko模块加载到内核，并且查看scull.ko驱动
④ 查看当前设备使用的主设备号，主设备号为260
⑤ 首先应该在/dev/目录下创建与该驱动程序相对应的文件节点，查看创建好的驱动程序节点文件并修改scull的权限。
⑥ 编写test.c程序，来对驱动程序进行测试。编译并执行该程序
移除驱动模块
加入内核源码树里面
① 把驱动程序（模块程序）拷贝到内核源码树根目录下/drivers/char下
② 编译配置文件Kconfig，加入驱动选项，使之在make menuconfig的时候出现改模块选项
③ 在内核根目录下执行make menuconfig
④ 没有安装curses库，安装。
⑤ 在内核根目录下执行make menuconfig，找到驱动模块，设置启动为M
⑥ 在模块文件所在目录的Makefile中加入要编译的驱动模块文件
⑦ 在源代码根目录linux下，执行make bzImage后执行make modules
⑧ 在char目录下查看得知device1.ko已经存在
⑨ 用lsmod指令安装模块文件，再对驱动程序进行测试。编译并执行该程序
代码：
#ifndef _MEMDEV_H_
#define _MEMDEV_H_ #ifndef MEMDEV_MAJOR
#define MEMDEV_MAJOR 260 /*预设的mem的主设备号*/
#endif #ifndef MEMDEV_NR_DEVS
#define MEMDEV_NR_DEVS 2 /*设备数*/
#endif #ifndef MEMDEV_SIZE
#define MEMDEV_SIZE 4096
#endif /*mem设备描述结构体*/
struct mem_dev
{
char *data;
unsigned long size;
}; #endif /* _MEMDEV_H_ */
scull.h
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/switch_to.h>
#include <asm/uaccess.h>
#include <linux/slab.h> #include "scull.h" static int mem_major = MEMDEV_MAJOR; module_param(mem_major, int, S_IRUGO); struct mem_dev *mem_devp; /*设备结构体指针*/ struct cdev cdev; /*文件打开函数*/
int mem_open(struct inode *inode, struct file *filp)
{
struct mem_dev *dev; /*获取次设备号*/
int num = MINOR(inode->i_rdev); if (num >= MEMDEV_NR_DEVS)
return -ENODEV;
dev = &mem_devp[num]; /*将设备描述结构指针赋值给文件私有数据指针*/
filp->private_data = dev; return ;
} /*文件释放函数*/
int mem_release(struct inode *inode, struct file *filp)
{
return ;
} /*读函数*/
static ssize_t mem_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = ;
struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*/ /*判断读位置是否有效*/
if (p >= MEMDEV_SIZE)
return ;
if (count > MEMDEV_SIZE - p)
count = MEMDEV_SIZE - p; /*读数据到用户空间*/
if (copy_to_user(buf, (void*)(dev->data + p), count))
{
ret = - EFAULT;
}
else
{
*ppos += count;
ret = count; printk(KERN_INFO "read %d bytes(s) from %d\n", count, p);
} return ret;
} /*写函数*/
static ssize_t mem_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = ;
struct mem_dev *dev = filp->private_data; /*获得设备结构体指针*/ /*分析和获取有效的写长度*/
if (p >= MEMDEV_SIZE)
return ;
if (count > MEMDEV_SIZE - p)
count = MEMDEV_SIZE - p; /*从用户空间写入数据*/
if (copy_from_user(dev->data + p, buf, count))
ret = - EFAULT;
else
{
*ppos += count;
ret = count; printk(KERN_INFO "written %d bytes(s) from %d\n", count, p);
} return ret;
} /* seek文件定位函数 */
static loff_t mem_llseek(struct file *filp, loff_t offset, int whence)
{
loff_t newpos; switch(whence) {
case : /* SEEK_SET */
newpos = offset;
break; case : /* SEEK_CUR */
newpos = filp->f_pos + offset;
break; case : /* SEEK_END */
newpos = MEMDEV_SIZE - + offset;
break; default: /* can't happen */
return -EINVAL;
}
if ((newpos<) || (newpos>MEMDEV_SIZE))
return -EINVAL; filp->f_pos = newpos;
return newpos; } /*文件操作结构体*/
static const struct file_operations mem_fops =
{
.owner = THIS_MODULE,
.llseek = mem_llseek,
.read = mem_read,
.write = mem_write,
.open = mem_open,
.release = mem_release,
}; /*设备驱动模块加载函数*/
static int memdev_init(void)
{
int result;
int i; dev_t devno = MKDEV(mem_major, ); /* 静态申请设备号*/
if (mem_major)
result = register_chrdev_region(devno, , "memdev");
else /* 动态分配设备号 */
{
result = alloc_chrdev_region(&devno, , , "memdev");
mem_major = MAJOR(devno);
} if (result < )
return result; /*初始化cdev结构*/
cdev_init(&cdev, &mem_fops);
cdev.owner = THIS_MODULE;
cdev.ops = &mem_fops; /* 注册字符设备 */
cdev_add(&cdev, MKDEV(mem_major, ), MEMDEV_NR_DEVS); /* 为设备描述结构分配内存*/
mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL);
if (!mem_devp) /*申请失败*/
{
result = - ENOMEM;
goto fail_malloc;
}
memset(mem_devp, , sizeof(struct mem_dev)); /*为设备分配内存*/
for (i=; i < MEMDEV_NR_DEVS; i++)
{
mem_devp[i].size = MEMDEV_SIZE;
mem_devp[i].data = kmalloc(MEMDEV_SIZE, GFP_KERNEL);
memset(mem_devp[i].data, , MEMDEV_SIZE);
} return ; fail_malloc:
unregister_chrdev_region(devno, ); return result;
} /*模块卸载函数*/
static void memdev_exit(void)
{
cdev_del(&cdev); /*注销设备*/
kfree(mem_devp); /*释放设备结构体内存*/
unregister_chrdev_region(MKDEV(mem_major, ), ); /*释放设备号*/
} MODULE_AUTHOR("David Xie");
MODULE_LICENSE("GPL"); module_init(memdev_init);
module_exit(memdev_exit);
scull.c
obj-m +=scull.o
all:
make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) modules
clean:
make -C /lib/modules/$(shell uname -r)/build M=$(shell pwd) clean
Makefile
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <linux/i2c.h>
#include <linux/fcntl.h> int main()
{
int fd;
char buf[]="this is a test!"; char buf_read[]; if((fd=open("/dev/scull",O_RDWR))==-) printf("open scull WRONG！\n");
else
printf("open scull SUCCESS!\n"); printf("buf is %s\n",buf); write(fd,buf,sizeof(buf)); lseek(fd,,SEEK_SET); read(fd,buf_read,sizeof(buf)); printf("buf_read is %s\n",buf_read); return ;
}
test.c
