Hi all,
(My environment is intel platform, HD4000 GPU, kernel 3.10.19,
logitech 270 webcam)
As title said, I discover this issue when I run the program
shown by Laurent Pinchart:
http://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg54806.html
If the frame is (width, height) = (640, 480), DMABUF works well.
If the frame is (width, height) = (160, 120), v4lfd receives no event.
And I dig into drm kernel code, find that: i915_gem_create will create
a GPU buffer object on intel platform. The size of GPU bo will be
bigger than frame size, for the reason that i915_gem_create will
roundup the bo size to multiple of PAGE_SIZE when the frame is (width,
height) = (160, 120).
For (width, height) = (640, 480), the frame size is already multiple
of PAGE_SIZE, so GPU bo is exactly equal to frame size.
I also dump the uvc driver infomation, there is some infomation i
think maybe important:
uvcvideo: Stream 1 error event 07 01 len 4
Looking forward to the discussion!
Thanks,
Chuanbo Weng
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