经典]Linux内核中ioremap映射的透彻理解【转】

#define writeb(b,addr) (*(volatile unsigned char *) __io_virt(addr) = (b))
#define writew(b,addr) (*(volatile unsigned short *) __io_virt(addr) = (b))
#define writel(b,addr) (*(volatile unsigned int *) __io_virt(addr) = (b))

#define memset_io(a,b,c) memset(__io_virt(a),(b),(c))
#define memcpy_fromio(a,b,c) memcpy((a),__io_virt(b),(c))
#define memcpy_toio(a,b,c) memcpy(__io_virt(a),(b),(c))

　　if (rtc_tm->tm_sec == 0) {
　　　/* Re-read all BCD registers in case of BCDSEC is 0.
　　　See RTC section at the manual for more info. */
　　　goto read_rtc_bcd_time;
　　}
　}
　spin_unlock_irq(&rtc_lock);

　BCD_TO_BIN(rtc_tm->tm_year);
　BCD_TO_BIN(rtc_tm->tm_mon);
　BCD_TO_BIN(rtc_tm->tm_mday);
　BCD_TO_BIN(rtc_tm->tm_hour);
　BCD_TO_BIN(rtc_tm->tm_min);
　BCD_TO_BIN(rtc_tm->tm_sec);

　/* The epoch of tm_year is 1900 */
　rtc_tm->tm_year += RTC_LEAP_YEAR - 1900;

　/* tm_mon starts at 0, but rtc month starts at 1 */
　rtc_tm->tm_mon--;
}

MODULE_PARM(mem_start, "i");
MODULE_PARM(mem_size, "i");

static int mem_start = 101, mem_size = 10;
static char *reserve_virt_addr;
static int major;

int mmapdrv_open(struct inode *inode, struct file *file);
int mmapdrv_release(struct inode *inode, struct file *file);
int mmapdrv_mmap(struct file *file, struct vm_area_struct *vma);

static struct file_operations mmapdrv_fops =
{
　owner: THIS_MODULE, mmap: mmapdrv_mmap, open: mmapdrv_open, release:
　mmapdrv_release,
};

int init_module(void)
{
　if ((major = register_chrdev(0, "mmapdrv", &mmapdrv_fops)) < 0)
　{
　　printk("mmapdrv: unable to register character device/n");
　　return ( - EIO);
　}
　printk("mmap device major = %d/n", major);

　printk("high memory physical address 0x%ldM/n", virt_to_phys(high_memory) /
1024 / 1024);

　reserve_virt_addr = ioremap(mem_start *1024 * 1024, mem_size *1024 * 1024);
　printk("reserve_virt_addr = 0x%lx/n", (unsigned long)reserve_virt_addr);
　if (reserve_virt_addr)
　{
　　int i;
　　for (i = 0; i < mem_size *1024 * 1024; i += 4)
　　{
　　　reserve_virt_addr[i] = 'a';
　　　reserve_virt_addr[i + 1] = 'b';
　　　reserve_virt_addr[i + 2] = 'c';
　　　reserve_virt_addr[i + 3] = 'd';
　　}
　}
　else
　{
　　unregister_chrdev(major, "mmapdrv");
　　return - ENODEV;
　}
　return 0;
}

/* remove the module */
void cleanup_module(void)
{
　if (reserve_virt_addr)
　　iounmap(reserve_virt_addr);

　unregister_chrdev(major, "mmapdrv");
　return ;
}

int mmapdrv_open(struct inode *inode, struct file *file)
{
　MOD_INC_USE_COUNT;
　return (0);
}

int mmapdrv_release(struct inode *inode, struct file *file)
{
　MOD_DEC_USE_COUNT;
　return (0);
}

int mmapdrv_mmap(struct file *file, struct vm_area_struct *vma)
{
　unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
　unsigned long size = vma->vm_end - vma->vm_start;

　if (size > mem_size *1024 * 1024)
　{
　　printk("size too big/n");
　　return ( - ENXIO);
　}

　offset = offset + mem_start * 1024 * 1024;

　/* we do not want to have this area swapped out, lock it */
　vma->vm_flags |= VM_LOCKED;
　if (remap_page_range(vma, vma->vm_start, offset, size, PAGE_SHARED))
　{
　　printk("remap page range failed/n");
　　return - ENXIO;
　}
　return (0);
}