Re: DMABUF doesn't work when frame size not equal to the size of GPU bo

[Seung-Woo Kim <sw0312.kim@samsung.com>]

Hello,

On 2014년 01월 02일 11:22, Chuanbo Weng wrote:
> Hi Laurent and Tomasz,
>        As I said in my previous email, you can download the code from
> the github address.
> I think you can easily reproduce this issue by running my program
> (Especially Laurent) and
> get more information from this program.
>        Could you please tell me whether you have reproduced this issue?
> 
> 
> Thanks,
> Chuanbo Weng
> 
> 2013/12/31 Laurent Pinchart <laurent.pinchart@ideasonboard.com>:
>> Hi Chuanbo,
>>
>> On Tuesday 31 December 2013 19:21:09 Chuanbo Weng wrote:
>>> 2013/12/31 Tomasz Stanislawski <t.stanislaws@samsung.com>:
>>>> Hi Chuanbo Weng,
>>>>
>>>> I suspect that the problem might be caused by difference
>>>> between size of DMABUF object and buffer size in V4L2.
>>>
>>> Thanks for your reply! I agree with you because my experiment prove it
>>> (Even when the bo is bigget than frame size, not smaller!!!).
>>>
>>>> What is the content of v4l2_format returned by VIDIOC_G_FMT?
>>>
>>> The content is V4L2_PIX_FMT_YUYV. (And if the content V4L2_PIX_FMT_MJPEG,
>>> this issue doesn't happen.)
>>
>> Could you please give us the content of all the other fields ?
>>
>>>> What is the content of V4l2_buffer structure passed by VIDIOC_QBUF?
>>
>> Same here.
>>

Did you check the result of VIDIOC_QBUF? I have similar issue on my
environment, so I added debug log for failure of QBUF as "[media]
videobuf2: Add log for size checking error in __qbuf_dmabuf" to clarify.

As your comment, DRM_IOCTL_MODE_CREATE_DUMB creates buffers aligned with
PAGE_SIZE, and size of DMABUF exported from GEM with PRIME ioctl is same
with the GEM, so the size is aligned with PAGE_SIZE.

In Videobuf2 of V4L2, __qbuf_dmabuf() checks passed buffer size, or
DMABUF size if passed size is 0, with size assigned by queue_setup
callback of the v4l2 driver. The v4l2 driver assigns the size calculated
from resolution and format, and usually *it is not aligned with
PAGE_SIZE* even though internal allocation is aligned. So the check
routine of size in __qbuf_dmabuf() returns failure.

I am not sure about queue_setup of UVC driver, but it seems same issue.

Maybe we can add PAGE_ALIGN for size from queue_setup in the
__qbuf_dmabuf() like __vb2_buf_mem_alloc() or vb2_mmap().

Regards,
- Seung-Woo Kim

>>> The fd in v4l2_buffer structure is fd of gem object created by
>>> DRM_IOCTL_MODE_CREATE_DUMB.
>>>
>>> I've upload the program that can reproduce this issue on intel platform. You
>>> just need to clone it from
>>> https://github.com/strgnm/v4l2-dmabuf-test.git
>>> Then build and run as said in README.
>>
>> --
>> Regards,
>>
>> Laurent Pinchart
>>
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-- 
Seung-Woo Kim
Samsung Software R&D Center
--