* buffer index when streaming user-ptr buffers
@ 2011-06-14 15:50 Michael Jones
2011-06-14 17:01 ` Laurent Pinchart
0 siblings, 1 reply; 2+ messages in thread
From: Michael Jones @ 2011-06-14 15:50 UTC (permalink / raw)
To: Linux Media Mailing List; +Cc: Laurent Pinchart, Sakari Ailus
In the V4L2 spec, the description for v4l2_buffer.index says "This field
is only used for memory mapping I/O..."
However, in v4l-utils/contrib/capture-example.c, even user-pointer
buffers are indeed given a buf.index before being passed to VIDIOC_QBUF.
And at least in the OMAP ISP driver, this information is relied upon in
QBUF regardless of V4L2_MEMORY_MMAP/USERPTR. videobuf-core also uses
v4l2_buffer->index even if b->memory == V4L2_MEMORY_USERPTR.
Is this a bug in the OMAP driver and videobuf-core, and an unnecessary
assignment in capture-example? Or is the V4L2 spec out of touch/ out of
date?
-Michael
MATRIX VISION GmbH, Talstrasse 16, DE-71570 Oppenweiler
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: buffer index when streaming user-ptr buffers
2011-06-14 15:50 buffer index when streaming user-ptr buffers Michael Jones
@ 2011-06-14 17:01 ` Laurent Pinchart
0 siblings, 0 replies; 2+ messages in thread
From: Laurent Pinchart @ 2011-06-14 17:01 UTC (permalink / raw)
To: Michael Jones; +Cc: Linux Media Mailing List, Sakari Ailus
Hi Michael,
On Tuesday 14 June 2011 17:50:13 Michael Jones wrote:
> In the V4L2 spec, the description for v4l2_buffer.index says "This field
> is only used for memory mapping I/O..."
>
> However, in v4l-utils/contrib/capture-example.c, even user-pointer
> buffers are indeed given a buf.index before being passed to VIDIOC_QBUF.
> And at least in the OMAP ISP driver, this information is relied upon in
> QBUF regardless of V4L2_MEMORY_MMAP/USERPTR. videobuf-core also uses
> v4l2_buffer->index even if b->memory == V4L2_MEMORY_USERPTR.
>
> Is this a bug in the OMAP driver and videobuf-core, and an unnecessary
> assignment in capture-example? Or is the V4L2 spec out of touch/ out of
> date?
The spec is out of date. The index field is used for userptr buffers as well.
--
Regards,
Laurent Pinchart
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