Linux符设备驱动编程

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