Re: [PATCH] videobuf2-dma-sg: Support io userptr operations on io memory

Ricardo Ribalda Delgado
2013-11-25T09:00:07Z

Hello Mathias

Memory managing is definately not my topic. I have done the same as in
vb2-dmacontig, and it has worked on my driver (out of tree).

I think that if there is something wrong it will also be wrong on the
dmacontig part, and much more drivers would be affected, so please
also take a look to videobuf2-dma-contig.c and check if there is
something wrong there.

Best Regards!

On Mon, Nov 11, 2013 at 12:36 PM, Matthias Wächter
<matthias.waechter@tttech.com> wrote:
>> @@ -180,7 +186,26 @@ static void *vb2_dma_sg_get_userptr(void
>> *alloc_ctx, unsigned long vaddr,
>> if (!buf->pages)
>> return NULL;
>>
>> - num_pages_from_user = get_user_pages(current, current->mm,
>> + buf->vma = find_vma(current->mm, vaddr);
>> + if (!buf->vma) {
>> + dprintk(1, "no vma for address %lu\n", vaddr);
>> + return NULL;
>> + }
>> +
>> + if (vma_is_io(buf->vma)) {
>> + for (num_pages_from_user = 0;
>> + num_pages_from_user < buf->num_pages;
>> + ++num_pages_from_user, vaddr += PAGE_SIZE) {
>> + unsigned long pfn;
>> +
>> + if (follow_pfn(buf->vma, vaddr, &pfn)) {
>> + dprintk(1, "no page for address %lu\n", vaddr);
>> + break;
>> + }
>> + buf->pages[num_pages_from_user] = pfn_to_page(pfn);
>> + }
>> + } else
>> + num_pages_from_user = get_user_pages(current, current->mm,
>> vaddr & PAGE_MASK,
>> buf->num_pages,
>> write,
>
> Can you safely assume that your userptr will cover only one vma? At least, get_user_pages (calling __get_user_pages) does not assume that and calls find_vma() whenever vma->vm_end is reached.
>
> – Matthias
>
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--
Ricardo Ribalda