Hi Guennadi,
On Tuesday 05 April 2011 14:39:19 Guennadi Liakhovetski wrote:
> On Tue, 5 Apr 2011, Laurent Pinchart wrote:
> > On Friday 01 April 2011 10:13:02 Guennadi Liakhovetski wrote:
> > > A possibility to preallocate and initialise buffers of different sizes
> > > in V4L2 is required for an efficient implementation of asnapshot mode.
> > > This patch adds three new ioctl()s: VIDIOC_CREATE_BUFS,
> > > VIDIOC_DESTROY_BUFS, and VIDIOC_SUBMIT_BUF and defines respective data
> > > structures.
[snip]
> > > diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> > > index aa6c393..b6ef46e 100644
> > > --- a/include/linux/videodev2.h
> > > +++ b/include/linux/videodev2.h
> > > @@ -1847,6 +1847,26 @@ struct v4l2_dbg_chip_ident {
[snip]
> > > +/* struct v4l2_createbuffers::flags */
> > > +#define V4L2_BUFFER_FLAG_NO_CACHE_INVALIDATE (1 << 0)
> >
> > Shouldn't cache management be handled at submit/qbuf time instead of
> > being a buffer property ?
>
> hmm, I'd prefer fixing it at create. Or do you want to be able to create
> buffers and then submit / queue them with different flags?...
That's the idea, yes. I'm not sure yet how useful that would be though.
[snip]
> > > +
> > >
> > > /*
> > >
> > > * I O C T L C O D E S F O R V I D E O D E V I C E S
> > > *
> > >
> > > @@ -1937,6 +1957,10 @@ struct v4l2_dbg_chip_ident {
> > >
> > > #define VIDIOC_SUBSCRIBE_EVENT _IOW('V', 90, struct
> > >
> > > v4l2_event_subscription) #define VIDIOC_UNSUBSCRIBE_EVENT _IOW('V', 91,
> > > struct v4l2_event_subscription)
> > >
> > > +#define VIDIOC_CREATE_BUFS _IOWR('V', 92, struct
> > > v4l2_create_buffers)
> > > +#define VIDIOC_DESTROY_BUFS _IOWR('V', 93, struct v4l2_buffer_span)
> >
> > Just throwing an idea in here, what about using the same structure for
> > both ioctls ? Or even a single ioctl for both create and destroy, like
> > we do with REQBUFS ?
>
> Personally, tbh, I don't like either of them. The first one seems an
> overkill - you don't need all those fields for destroy. The second one is
> a particular case of the first one, plus it adds confusion by re-using the
> ioctl:-) Where with REQBUFS we could just set count = 0 to say - release
> all buffers, with this one we need index and count, so, we'd need one more
> flag to distinguish between create / destroy...
OK, idea dismissed :-)
--
Regards,
Laurent Pinchart
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