Re: AW: AW: v4l2_buffer with PBO mapped memory

[Hans Verkuil <hverkuil@xs4all.nl>]

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
>>
>> This message is subject to the following terms and conditions: MAIL
>> DISCLAIMER<http://www.barco.com/en/maildisclaimer>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-media" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> This message is subject to the following terms and conditions: MAIL DISCLAIMER<http://www.barco.com/en/maildisclaimer>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>