On 04/15/2014 08:04 AM, Thomas Scheuermann wrote:
> Hi Laurent,
>
> On 11.04.2014 07:56, Thomas Scheuermann wrote:
>> Hi Laurent,
>>
>> On 07.04.2014 01:37, Laurent Pinchart wrote:
>>> Hi Thomas,
>>>
>>> On Friday 04 April 2014 20:01:33 Scheuermann, Mail wrote:
>>>> Hi Laurent,
>>>>
>>>> I've done the following:
>>>>
>>>> echo 3 >/sys/module/videobuf2_core/parameters/debug
>>>>
>>>> and found in /var/log/kern.log after starting my program:
>>>>
>>>> [239432.535077] vb2: Buffer 0, plane 0 offset 0x00000000
>>>> [239432.535080] vb2: Buffer 1, plane 0 offset 0x001c2000
>>>> [239432.535082] vb2: Buffer 2, plane 0 offset 0x00384000
>>>> [239432.535083] vb2: Allocated 3 buffers, 1 plane(s) each
>>>> [239432.535085] vb2: qbuf: userspace address for plane 0 changed,
>>>> reacquiring memory
>>>> [239432.535087] vb2: qbuf: failed acquiring userspace memory for
>>>> plane 0
>>> This confirms everything is working properly up to the point where
>>> videobuf2-
>>> vmalloc fails to acquire the user pointer memory. The problem comes from
>>> vb2_vmalloc_get_userptr() in
>>> drivers/media/v4l2-core/videobuf2-vmalloc.c.
>>> Unfortunately that function lacks debugging. Are you familiar enough
>>> with
>>> kernel programming to add printk statements there and see where it
>>> fails ?
>> I was able to put some debug output in vb2_vmalloc_get_userptr.
>> A call to 'vb2_get_contig_userptr' failed.
Unless I am mistaken vb2_get_contig_userptr() requires that the userptr
points to physically contiguous memory, but that should not be a
requirement for videobuf2-vmalloc.
Pawel, any idea why vb2_get_contig_userptr() is used here?
Regards,
Hans
>> I will also put some debug code there to get more information.
>
> In vb2_get_contig_userptr I saw that the call to 'follow_pfn' failed and
> returned -22.
> Do you know what the problem here is?
>>>> [239432.535088] vb2: qbuf: buffer preparation failed: -22
>>>> [239432.535128] vb2: streamoff: not streaming
>>
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