mmap疑问
在学习mmap,驱动如下:#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/pci.h>
#include <linux/gpio.h>
#define DEVICE_NAME "mymap"
static unsigned char *buffer;
static int my_open(struct inode *inode, struct file *file)
{
return 0;
}
static int my_map(struct file *filp, struct vm_area_struct *vma)
{
unsigned long page;
unsigned char i;
unsigned long start = (unsigned long)vma->vm_start;
//unsigned long end =(unsigned long)vma->vm_end;
unsigned long size = (unsigned long)(vma->vm_end - vma->vm_start);
page = virt_to_phys(buffer);
if(remap_pfn_range(vma,start,page>>PAGE_SHIFT,size,PAGE_SHARED))
return -1;
for(i=0;i<1000;i++)
buffer = i;
return 0;
}
static struct file_operations dev_fops = {
.owner = THIS_MODULE,
.open = my_open,
.mmap = my_map,
};
static struct miscdevice misc = {
.minor = MISC_DYNAMIC_MINOR,
.name = DEVICE_NAME,
.fops = &dev_fops,
};
static int __init dev_init(void)
{
int ret;
ret = misc_register(&misc);
buffer = (unsigned char *)kmalloc(16*PAGE_SIZE,GFP_KERNEL);
//将该段内存设置为保留
SetPageReserved(virt_to_page(buffer));
return ret;
}
static void __exit dev_exit(void)
{
//注销设备
misc_deregister(&misc);
//清除保留
ClearPageReserved(virt_to_page(buffer));
//释放内存
kfree(buffer);
}
module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("somebody");
测试代码如下:
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#define PAGE_SIZE 4096
int main(int argc , char *argv[])
{
int fd;
int i;
unsigned char *p_map;
//打开设备
fd = open("/dev/mymap",O_RDWR);
if(fd < 0)
{
printf("open fail\n");
exit(1);
}
//内存映射
p_map = (unsigned char *)mmap(0, 16*PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,fd, 0);
if(p_map == MAP_FAILED)
{
printf("mmap fail\n");
goto here;
}
for(i=0;i<1000;i++)
printf("%d\n",p_map);
here:
munmap(p_map,16*PAGE_SIZE);
return 0;
}
驱动加载成功,应用程序运行之后,终端就不响应了,然后过了一会儿,开发板重启了。
当我把i的值设为200的时候是可以的,没有任何问题。为什么1000就不行了呢。求问原因。谢谢。
my_map写的太简单了,你申请的时候不要申请那么大,要么就你完善下my_map, embedsky_lhh 发表于 2012-10-22 11:20 static/image/common/back.gif
my_map写的太简单了,你申请的时候不要申请那么大,要么就你完善下my_map,
没明白你的意思?怎么才叫完善? 月骅 发表于 2012-10-22 17:37 static/image/common/back.gif
没明白你的意思?怎么才叫完善?
完善这个我也是模糊概念,
对remap_pfn_range的熟悉度不过,但模仿总行的这个是LCD的显存mmap实现方式,你可到你的内核看下
static int
fb_mmap(struct file *file, struct vm_area_struct * vma)
{
struct fb_info *info = file_fb_info(file);
struct fb_ops *fb;
unsigned long off;
unsigned long start;
u32 len;
if (!info)
return -ENODEV;
if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))
return -EINVAL;
off = vma->vm_pgoff << PAGE_SHIFT;
fb = info->fbops;
if (!fb)
return -ENODEV;
mutex_lock(&info->mm_lock);
if (fb->fb_mmap) {
int res;
res = fb->fb_mmap(info, vma);
mutex_unlock(&info->mm_lock);
return res;
}
/* frame buffer memory */
start = info->fix.smem_start;
len = PAGE_ALIGN((start & ~PAGE_MASK) + info->fix.smem_len);
if (off >= len) {
/* memory mapped io */
off -= len;
if (info->var.accel_flags) {
mutex_unlock(&info->mm_lock);
return -EINVAL;
}
start = info->fix.mmio_start;
len = PAGE_ALIGN((start & ~PAGE_MASK) + info->fix.mmio_len);
}
mutex_unlock(&info->mm_lock);
start &= PAGE_MASK;
if ((vma->vm_end - vma->vm_start + off) > len)
return -EINVAL;
off += start;
vma->vm_pgoff = off >> PAGE_SHIFT;
/* This is an IO map - tell maydump to skip this VMA */
vma->vm_flags |= VM_IO | VM_RESERVED;
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
fb_pgprotect(file, vma, off);
if (io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
vma->vm_end - vma->vm_start, vma->vm_page_prot))
return -EAGAIN;
return 0;
} embedsky_lhh 发表于 2012-10-23 15:59 static/image/common/back.gif
完善这个我也是模糊概念,
对remap_pfn_range的熟悉度不过,但模仿总行的这个是LCD的显存mmap实现方式, ...
原来是unsigned char 死循环。。。我2了。。。 本帖最后由 月骅 于 2012-11-9 14:07 编辑
embedsky_lhh 发表于 2012-10-23 15:59 static/image/common/back.gif
完善这个我也是模糊概念,
对remap_pfn_range的熟悉度不过,但模仿总行的这个是LCD的显存mmap实现方式, ...
版主啊,我再问个问题啊。
当我在应用程序中执行这句时:p_map = (unsigned char *)mmap(0, 16*PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,fd, 0);驱动中中的my_map执行了一遍,buffer的数值是在这个时候获得的。我这样的理解对不对?
如果不对,p_map的数值是什么时候获得的? 月骅 发表于 2012-11-9 14:06 static/image/common/back.gif
版主啊,我再问个问题啊。
当我在应用程序中执行这句时:驱动中中的my_map执行了一遍,buffer的数值是在 ...
你可先下内存拷贝还有DMA内存,
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