On Thu, Jul 07, 2011 at 03:32:54PM +0800, bill wrote:

Hi, Greg

I've been reading the UIO code, one place puzzled me a lot.
May I ask one question about it?

-------------------------------------------------------------------------------
drivers/uio/uio.c
static int uio_find_mem_index(struct vm_area_struct *vma)
{
    int mi;
    struct uio_device *idev = vma->vm_private_data;

    for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
        if (idev->info->mem[mi].size == 0)
            return -1;
        if (vma->vm_pgoff == mi)
            return mi;
    }
    return -1;
}

I don't get it why use vma->vm_pgoff as the index for struct uio_mem mem[MAX_UIO_MAPS],
Suppose there are twohardware memory space, if user intends to map the 2nd mem, then
the last parameter of mmap should be 1,

mapaddr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED,
               fd, 1);

Is my understanding correct?

I really don't know, sorry.

But Hans should know, Hans?