linux驱动之mmap实例

// Linux Device Driver Template/Skeleton with mmap
// Kernel Module
#include <linux/module.h>
#include <linux/init.h>
#include <linux/version.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <linux/slab.h>
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
#include <linux/wrapper.h>
#endif
#define SKELETON_MAJOR 240
#define SKELETON_NAME "skeleton"
#define CASE1 1
#define CASE2 2
static unsigned int counter = 0;
static char string [128];
static int data;
//#define USEASCII
#ifdef USEASCII
static char *kmalloc_area = NULL;
static char *kmalloc_ptr = NULL;
#else
static unsigned int *kmalloc_area = NULL;
static unsigned int *kmalloc_ptr = NULL;
#endif
#define LEN (64*1024)
unsigned long virt_addr;
DECLARE_WAIT_QUEUE_HEAD(skeleton_wait);
static int data_not_ready = 0;
// open function - called when the "file" /dev/skeleton is opened in userspace
static int skeleton_open (struct inode *inode, struct file *file) {
 printk("skeleton_openn");
 // we could do some checking on the flags supplied by "open"
 // i.e. O_NONBLOCK
 // -> set some flag to disable interruptible_sleep_on in skeleton_read
 return 0;
}
// close function - called when the "file" /dev/skeleton is closed in userspace 
static int skeleton_release (struct inode *inode, struct file *file) {
 printk("skeleton_releasen");
 return 0;
}
// read function called when from /dev/skeleton is read
static ssize_t skeleton_read (struct file *file, char *buf,
  size_t count, loff_t *ppos) {
 int len, err;
 
 // check if we have data - if not, sleep
 // wake up in interrupt_handler
 while (data_not_ready) {
  interrupt