Hi Hans, On Wed, Jun 22, 2022 at 12:00:58PM +0200, Hans Verkuil wrote: > On 22/06/2022 11:44, Laurent Pinchart wrote: > > On Wed, Jun 22, 2022 at 11:31:43AM +0200, Hans Verkuil wrote: > >> Add support for two new (un)prepare_streaming queue ops that are called > >> when the user calls VIDIOC_STREAMON and STREAMOFF (or closes the fh). > >> > >> This gives drivers a callback to validate the video pipeline and claim > >> or release streaming resources at the time that userspace indicates > >> that it wants to start streaming (VIDIOC_STREAMON) rather than when > >> the actual DMA engine kicks in (the start_streaming callback). This > >> is relevant for drivers that needs a minimum of X buffers before the > >> DMA can start. The actual pipeline validation needs to happen sooner > >> to avoid unnecessary errors at VIDIOC_QBUF time. > >> > >> As a bonus this allows us to move the horrible call to > >> v4l_vb2q_enable_media_source() in vb2_core_streamon() to the au0828 > >> driver (currently the only driver that uses this feature). > > > > Can we drop the horrible .enable_source() from media_device too ? :-) > > The second patch helps a bit with that, at least it's out of vb2. > > > > >> That call never belonged in vb2, but it had the same purpose as the > >> new prepare_streaming op: validate the pipeline. > >> > >> This is a follow-up from my previous RFCv2: > >> > >> https://patchwork.linuxtv.org/project/linux-media/patch/ba4bca14-488f-94ea-48d9-e7343103c5aa@xxxxxxxxx/ > >> > >> I would like to get consensus for this series. > > > > I don't like it much. vb2 is already doing too much in my opinion, > > growing it isn't the right way to fix it. > > We disagree on that :-) I like polite and constructive disagreements, they help moving forward :-) > > I'm still working on a new version of the V4L2 streams series that may > > conflict with this, I'd propose discussing the two together. > > What is the ETA for that? I don't mind waiting a few months, but if it > takes a lot longer, then I'd rather merge this first so Eugen can use it > in his atmel MC support. It's a kernel API, so it can always be changed > or removed later. I have a few other things to complete first, an dI plan to resume the work in the first half of July, to post a v12 before the end of the month. > >> Hans Verkuil (2): > >> vb2: add (un)prepare_streaming queue ops > >> vb2/au0828: move the v4l_vb2q_enable_media_source to the au0828 driver > >> > >> .../media/common/videobuf2/videobuf2-core.c | 26 ++++++++++++++----- > >> drivers/media/usb/au0828/au0828-vbi.c | 2 ++ > >> drivers/media/usb/au0828/au0828-video.c | 1 + > >> include/media/videobuf2-core.h | 14 ++++++++++ > >> 4 files changed, 37 insertions(+), 6 deletions(-) -- Regards, Laurent Pinchart
