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Linux下的简单字符驱动--改自宋宝华《Linux驱动开发详解第2版》在kernel2.6.38通过,
实验过程：在fedora9虚拟机上完成交叉编译，生成mini6410_globalmem.ko, 复制到tiny6410开发板上。
可以用insmod及rmmod 添加删除
/* globalmem driver as an example of char device drivers
mini6410_globalmem.c
The initial developer of the original code is Baohua Song
<author@linuxdriver.cn>. All Rights Reserved.
======================================================================*/
#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 <linux/device.h>
#include <linux/slab.h>
#define GLOBALMEM_SIZE 0x1000 /*全局内存最大4K字节*/
#define MEM_CLEAR 0x1 /*清0全局内存*/
#define GLOBALMEM_MAJOR 233 /*预设的globalmem的主设备号*/
struct class * my_class;
static globalmem_major = GLOBALMEM_MAJOR;
/*globalmem设备结构体*/
struct globalmem_dev
{
struct cdev cdev ; /*cdev结构体*/
unsigned char mem [ GLOBALMEM_SIZE]; /*全局内存*/
struct semaphore sem ;
};
struct globalmem_dev * globalmem_devp; /*设备结构体指针*/
/*文件打开函数*/
int globalmem_open( struct inode * inode , struct file * filp )
{
/*将设备结构体指针赋值给文件私有数据指针*/
filp -> private_data = globalmem_devp;
return 0 ;
}
/*文件释放函数*/
int globalmem_release( struct inode * inode , struct file * filp )
{
return 0 ;
}
/* ioctl设备控制函数 after kernel2.6.36 remove ioctl,add unlocked_ioctl*/
static int globalmem_unlocked_ioctl( struct inode * inodep , struct file * filp , unsigned
int cmd , unsigned long arg )
{
struct globalmem_dev * dev = filp -> private_data; //获得设备结构体指针
switch ( cmd )
{
case MEM_CLEAR:
if ( down_interruptible(& dev -> sem ))
return - ERESTARTSYS;
memset( dev -> mem , 0 , GLOBALMEM_SIZE);
up(& dev -> sem );
printk( KERN_INFO "globalmem is set to zero/n" );
break ;
default :
return - EINVAL;
}
return 0 ;
}
/*读函数*/
static ssize_t globalmem_read( struct file * filp, char __user * buf, size_t size,
loff_t * ppos)
{
unsigned long p = * ppos;
unsigned int count = size;
int ret = 0 ;
struct globalmem_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 >= GLOBALMEM_SIZE)
return count ? - ENXIO: 0 ;
if ( count > GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;
if ( down_interruptible(& dev-> sem))
return - ERESTARTSYS;
/*内核空间->用户空间*/
if ( copy_to_user( buf, ( void *)( dev-> mem + p), count))
{
ret = - EFAULT;
}
else
{
* ppos += count;
ret = count;
printk( KERN_INFO "read %d bytes(s) from %d/n" , count, p);
}
up(& dev-> sem );
return ret;
}
/*写函数*/
static ssize_t globalmem_write( struct file * filp, const char __user * buf,
size_t size, loff_t * ppos)
{
unsigned long p = * ppos;
unsigned int count = size;
int ret = 0 ;
struct globalmem_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 >= GLOBALMEM_SIZE)
return count ? - ENXIO: 0 ;
if ( count > GLOBALMEM_SIZE - p)
count = GLOBALMEM_SIZE - p;
if ( down_interruptible(& dev-> sem))
return - ERESTARTSYS;
/*用户空间->内核空间*/
if ( copy_from_user( dev-> mem + p, buf, count)) //p是偏移，也就是写入的起始地址
ret = - EFAULT;
else
{
* ppos += count;
ret = count;
printk( KERN_INFO "written %d bytes(s) from %d/n" , count, p);
}
up(& dev-> sem );
return ret;
}
/* seek文件定位函数 */
static loff_t globalmem_llseek( struct file * filp , loff_t offset , int orig )
{
loff_t ret = 0 ;
switch ( orig )
{
case 0 : /*相对文件开始位置偏移*/
if ( offset < 0 )
{
ret = - EINVAL;
break ;
}
if (( unsigned int ) offset > GLOBALMEM_SIZE)
{
ret = - EINVAL;
break ;
}
filp -> f_pos = ( unsigned int ) offset ;
ret = filp -> f_pos;
break ;
case 1 : /*相对文件当前位置偏移*/
if (( filp -> f_pos + offset ) > GLOBALMEM_SIZE)
{
ret = - EINVAL;
break ;
}
if (( filp -> f_pos + offset ) < 0 )
{
ret = - EINVAL;
break ;
}
filp -> f_pos += offset ;
ret = filp -> f_pos;
break ;
default :
ret = - EINVAL;
break ;
}
return ret ;
}
/*文件操作结构体*/
static const struct file_operations globalmem_fops =
{
. owner = THIS_MODULE,
. llseek = globalmem_llseek,
. read = globalmem_read,
. write = globalmem_write,
. unlocked_ioctl = globalmem_unlocked_ioctl,
. open = globalmem_open,
. release = globalmem_release,
};
/*初始化并注册cdev*/
static void globalmem_setup_cdev( struct globalmem_dev * dev , int index )
{
int err , devno = MKDEV( globalmem_major, index );
cdev_init(& dev -> cdev , & globalmem_fops);
dev -> cdev . owner = THIS_MODULE;
dev -> cdev . ops = & globalmem_fops;
err = cdev_add(& dev -> cdev , devno , 1 );
if ( err )
printk( KERN_NOTICE "Error %d adding globalmem%d" , err , index );
}
/*设备驱动模块加载函数*/
int globalmem_init( void )
{
int result ;
dev_t devno = MKDEV( globalmem_major, 0 );
/* 申请设备号*/
if ( globalmem_major)
result = register_chrdev_region( devno , 1 , "globalmem" );
else /* 动态申请设备号 */
{
result = alloc_chrdev_region(& devno , 0 , 1 , "globalmem" );
globalmem_major = MAJOR( devno );
}
if ( result < 0 )
return result ;
/*kmalloc*/
globalmem_devp = kmalloc( sizeof ( struct globalmem_dev ), GFP_KERNEL);
if (! globalmem_devp) /*申请失败*/
{
result = - ENOMEM;
goto fail_malloc;
}
memset( globalmem_devp, 0 , sizeof ( struct globalmem_dev ));
globalmem_setup_cdev( globalmem_devp, 0 );
sema_init(& globalmem_devp-> sem , 1 ); //init_MUTEX(&globalmem_devp->sem);
/* create your own class under /sysfs */
/*class_create --> class_register()*/
my_class = class_create( THIS_MODULE, "globalmem" );
if ( IS_ERR( my_class)) {
printk( "Err: failed in creating class./n" );
goto fail_malloc;
}
/* register your own device in sysfs, and this will cause udev to create corresponding device node */
device_create( my_class, NULL, MKDEV( globalmem_major, 0 ), NULL, "globalmem" );
printk ( KERN_INFO "Registered character driver/n" );
return 0 ;
fail_malloc : unregister_chrdev_region( devno , 1 );
return result ;
}
/*模块卸载函数*/
void globalmem_exit( void )
{
cdev_del(& globalmem_devp-> cdev ); /*注销cdev*/
kfree( globalmem_devp); /*释放设备结构体内存*/
unregister_chrdev_region( MKDEV( globalmem_major, 0 ), 1 ); /*释放设备号*/
}
MODULE_AUTHOR( "Song Baohua" );
MODULE_LICENSE( "Dual BSD/GPL" );
module_param( globalmem_major, int , S_IRUGO);
module_init( globalmem_init);
module_exit( globalmem_exit);
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