国嵌memdev驱动试验

memdev驱动试验 

     今天开始驱动的学习，根据国嵌驱动开发视频一边学习，一边试验。国嵌视频上首先讲述字符驱动开发过程，memdev就是最好的例子。首先在看懂源码的基础上学习怎么将驱动装载到开发板。下面是memdev源码：

#ifndef _MEMDEV_H_#define _MEMDEV_H_#ifndef MEMDEV_MAJOR#define MEMDEV_MAJOR 260 //memdev采用静态分配设备号，不要和其它设备重复#endif#ifndef MEMDEV_NR_DEVS#define MEMDEV_NR_DEVS 2#endif#ifndef MEMDEV_SIZE#define MEMDEV_SIZE 4096#endifstruct mem_dev{char *data;unsigned long size;};#endif

 

/**********************************************memdev.c*********************************************/#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/system.h>#include <asm/uaccess.h>#include "memdev.h"static int mem_major = MEMDEV_MAJOR;module_param(mem_major,int,S_IRUGO);struct mem_dev *mem_devp;struct cdev cdev;int mem_open(struct inode *inode,struct file *filp){struct mem_dev *dev;int num = MINOR(inode->i_rdev);if(num >=MEMDEV_NR_DEVS)return -ENODEV;dev = &mem_devp[num];filp->private_data = dev;return 0;}int mem_release(struct inode *inode,struct file *filp){return 0;}static ssize_t mem_read(struct file *filp,char __user *buf,size_t size,loff_t *poss){unsigned long p = *poss;unsigned int count = size;int ret = 0;struct mem_dev *dev = filp->private_data;if(p >= MEMDEV_SIZE)return 0;if(count > MEMDEV_SIZE-p)count = MEMDEV_SIZE-p;if(copy_to_user(buf,(void*)(dev->data+p),count)){ret = -EFAULT;}else{*poss +=count;ret = count;printk(KERN_INFO "read %d bytes from %lu/n",count,p);}return ret;}static ssize_t mem_write(struct file *filp,const char __user *buf,size_t size,loff_t *poss){unsigned long p = *poss;unsigned int count = size;int ret=0;struct mem_dev *dev = filp->private_data;if(p>=MEMDEV_SIZE)return 0;if(count>MEMDEV_SIZE-p)count = MEMDEV_SIZE-p;if(copy_from_user(dev->data+p,buf,count)){ret = -EFAULT;}else{*poss += count;ret = count;printk(KERN_INFO "write %d bytes from %lu/n",count,p);}return ret;}static loff_t mem_llseek(struct file *filp,loff_t offset,int whence){loff_t newpos;switch(whence){case 0:newpos = offset;break;case 1:newpos = filp->f_pos + offset;break;case 2:newpos = MEMDEV_SIZE - 1 + offset;break;default:return -EINVAL;}if((newpos<0) || (newpos>MEMDEV_SIZE))return -EINVAL;filp->f_pos = newpos;return newpos;}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,};static int memdev_init(void){int result;int i;dev_t devno = MKDEV(mem_major,0);if(mem_major)result = register_chrdev_region(devno,2,"memdev");else{result = alloc_chrdev_region(&devno,0,2,"memdev");mem_major = MAJOR(devno);}if(result < 0)return result;cdev_init(&cdev,&mem_fops);cdev.owner = THIS_MODULE;cdev.ops = &mem_fops;cdev_add(&cdev,MKDEV(mem_major,0),MEMDEV_NR_DEVS);mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev),GFP_KERNEL);if(!mem_devp){result = -ENOMEM;goto fail_malloc;}memset(mem_devp,0,MEMDEV_NR_DEVS * sizeof(struct mem_dev));for(i=0;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,0,MEMDEV_SIZE);}return 0;fail_malloc:unregister_chrdev_region(devno,2);return result;}static void memdev_exit(void){cdev_del(&cdev);kfree(mem_devp);unregister_chrdev_region(MKDEV(mem_major,0),2);}MODULE_AUTHOR("Zechin Liao");MODULE_LICENSE("GPL");module_init(memdev_init);module_exit(memdev_exit);

 

ifneq ($(KERNELRELEASE),)obj-m:=memdev.oelseKERNELDIR:=/home/liao/image/linux-2.6.24PWD:=$(shell pwd)all:make -C $(KERNELDIR) M=$(PWD) modules ARCH=arm CROSS_COMPILE=arm-linux-clean:rm -rf *.ko *.o *.mod.c *.mod.o *.symversendif

执行make就会生成memdev.ko驱动文件，将编译好的驱动memdev.ko拷贝至开发板/lib/modules目录。

注意：驱动程序的编译依赖内核源代码，并且内核源代码（KERNELDIR指明）要与目标板运行的内核一致。

 

编写应用程序，对驱动程序测试

/********************************************* *memdevapp.c *********************************************/ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h> int main() { int fd; char buf[4096]; strcpy(buf,"This is a example of charactar devices driver"); printf("buf:%s/n",buf); fd=open("/dev/memdev0",O_RDWR); if(fd == -1) { printf("open memdev failed!/n"); return -1; } write(fd,buf,sizeof(buf)); lseek(fd,0,SEEK_SET); strcpy(buf,"nothing"); read(fd,buf,sizeof(buf)); printf("buf:%s/n",buf); return 0; }

 arm-linux-gcc –o memdevapp memdevapp.c编译应用程序，将其下载至开板

 

 

 

添加模块：

# cd /lib/modules

# insmod memdev.ko 

 

添加设备节点：

# cd /dev

# cat /proc/devices 查看设备号

# mknod memdev0 c 260 0

 

运行应用程序

# ./memdevapp

 

以上方法采用的动态编译驱动，也可以静态方式将驱动编译进内核

1.将memdev.h和memdev.c两个驱动源文件拷贝至内核linux-2.6.24/drivers/char目录

 

2.修改该目录下Kconfig文件，添加如下内容

config MEMDEV_DRIVER

             tristate "memdev driver"

             depends on MACH_SMDK2440

             default y if MACH_SMDK2440

             help

                 this option enables support for memdev experiment

 

3.修改该目录下Makefile，添加如下内容

obj-$(CONFIG_MEMDEV_DRIVER)      +=memdev.o

 

4.在make menuconfig时在字符设备中找到菜单项“memdev drinver”，选择为Y或M，编译进内核还是模块。