Hi Pavel, On Tuesday 23 February 2010 08:41:49 Pawel Osciak wrote: > >On Mon, 22 Feb 2010 00:12:18 +0100 > >Laurent Pinchart <laurent.pinch...@ideasonboard.com> wrote: > >> On Saturday 20 February 2010 15:00:21 Hans Verkuil wrote: > >> > 1) The spec mentions that the memory field should be set for > >> > VIDIOC_DQBUF. But videobuf doesn't need it and it makes no sense to > >> > me either unless it is for symmetry with VIDIOC_QBUF. Strictly > >> > speaking QBUF doesn't need it either, but it is a good sanity check. > >> > > >> > Can I remove the statement in the spec that memory should be set > >> > for DQBUF? The alternative is to add a check against the memory > >> > field in videobuf, but that's rather scary. > >> > >> In that case I would remove it for QBUF as well, and state that the > >> memory field must be ignored by drivers (but should they fill it when > >> returning from QBUF/DQBUF ?) > > > >Agree. It seems that the memory field is not useful at all in the struct > >v4l2_buffer if a same process does reqbuf, qbuf, dqbuf and querybuf. > > In the current multi-plane buffer proposal, the memory field is required > in querybuf, qbuf and dqbuf for the v4l2-ioctl.c code to be able to > determine whether the planes array should be copied from/to user along > with the buffer. > Just wanted to add another view to the problem, as multiplanes are accepted > yet of course.
Thanks for the reminder. I'm not against keeping the requirement for applications to set the memory field in the v4l2_buffer structure. QBUF and DQBUF should behave the same way though, they should both require the field to be set or not require it at all. > As for the REQBUF, I've always thought it'd be nice to be able to ask the > driver for the "recommended" number of buffers that should be used by > issuing a REQBUF with count=0... How would the driver come up with the number of recommended buffers ? -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
