Messages in this thread |  | | Subject | Re: [PATCH v7 2/6] [media] v4l: add 'unordered' flag to format description ioctl | From | Hans Verkuil <> | Date | Fri, 12 Jan 2018 13:05:06 +0100 |
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On 01/10/18 17:07, Gustavo Padovan wrote: > From: Gustavo Padovan <gustavo.padovan@collabora.com> > > For explicit synchronization it important for userspace to know if the > format being used by the driver can deliver the buffers back to userspace > in the same order they were queued with QBUF. > > Ordered streams fits nicely in a pipeline with DRM for example, where > ordered buffer are expected. > > Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com> > --- > Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 3 +++ > include/uapi/linux/videodev2.h | 1 + > 2 files changed, 4 insertions(+) > > diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst > index 019c513df217..368115f44fc0 100644 > --- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst > +++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst > @@ -116,6 +116,9 @@ one until ``EINVAL`` is returned. > - This format is not native to the device but emulated through > software (usually libv4l2), where possible try to use a native > format instead for better performance. > + * - ``V4L2_FMT_FLAG_UNORDERED`` > + - 0x0004 > + - This is a format that doesn't guarantee timely order of frames.
I'd rephrase this:
"This format doesn't guarantee ordered buffer handling. I.e. the order in which buffers are dequeued with VIDIOC_DQBUF may be different from the order in which they were queued with VIDIOC_QBUF."
(Use proper links to VIDIOC_(D)QBUF)
I would also like to see an example of a driver that uses this. The cobalt driver is a candidate for this.
Regards,
Hans
> > > Return Value > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > index 982718965180..58894cfe9479 100644 > --- a/include/uapi/linux/videodev2.h > +++ b/include/uapi/linux/videodev2.h > @@ -716,6 +716,7 @@ struct v4l2_fmtdesc { > > #define V4L2_FMT_FLAG_COMPRESSED 0x0001 > #define V4L2_FMT_FLAG_EMULATED 0x0002 > +#define V4L2_FMT_FLAG_UNORDERED 0x0004 > > /* Frame Size and frame rate enumeration */ > /* >
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