Hi Laurent, On 22/06/2022 12:08, Laurent Pinchart wrote: > 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. Looking at the latest v15 series there are no conflicts with this patch. Eugen posted a v11 of his "atmel-isc: driver redesign" series, and wants to use this functionality. I think with this change it is also possible to remove the enable_source callback from the mc. I can try to post a v2 that does this, if that's what it takes to convince you :-) Regards, Hans > >>>> 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(-) >
