Re: [PATCH v2 0/3] media: vimc: Allow multiple capture devices to use the same sensor

[Dafna Hirschfeld]

Hi

On 28.07.20 13:39, Kaaira Gupta wrote:
> On Mon, Jul 27, 2020 at 02:54:30PM -0300, Helen Koike wrote:
> > Hi,
> >
> > On 7/27/20 11:31 AM, Kieran Bingham wrote:
> > > Hi all,
> > >
> > > +Dafna for the thread discussion, as she's missed from the to/cc list.
> > >
> > >
> > > On 24/07/2020 13:21, Kaaira Gupta wrote:
> > > > On Fri, Jul 24, 2020 at 02:15:21PM +0200, Niklas SÃderlund wrote:
> > > > Hi,
> > > >
> > > > > Hi Kaaira,
> > > > >
> > > > > Thanks for your work.
> > > >
> > > > Thanks for yours :D
> > > >
> > > > > On 2020-07-24 17:32:10 +0530, Kaaira Gupta wrote:
> > > > > > This is version 2 of the patch series posted by Niklas for allowing
> > > > > > multiple streams in VIMC.
> > > > > > The original series can be found here:
> > > > > > https://patchwork.kernel.org/cover/10948831/
> > > > > >
> > > > > > This series adds support for two (or more) capture devices to be
> > > > > > connected to the same sensors and run simultaneously. Each capture device
> > > > > > can be started and stopped independent of each other.
> > > > > >
> > > > > > Patch 1/3 and 2/3 deals with solving the issues that arises once two
> > > > > > capture devices can be part of the same pipeline. While 3/3 allows for
> > > > > > two capture devices to be part of the same pipeline and thus allows for
> > > > > > simultaneously use.

I wonder if these two patches are enough, since each vimc entity also have
a 'process_frame' callback, but only one allocated frame. That means
that the 'process_frame' can be called concurrently by two different streams
on the same frame and cause corruption.

Thanks,
Dafna

> > > > > I'm just curious if you are aware of this series? It would replace the
> > > > > need for 1/3 and 2/3 of this series right?
> > > >
> > > > v3 of this series replaces the need for 1/3, but not the current version
> > > > (ie v4). v4 of patch 2/5 removes the stream_counter that is needed to
> > > > keep count of the calls to s_stream. Hence 1/3 becomes relevant again.
> > >
> > > So the question really is, how do we best make use of the two current
> > > series, to achieve our goal of supporting multiple streams.
> > >
> > > Having not parsed Dafna's series yet, do we need to combine elements of
> > > both ? Or should we work towards starting with this series and get
> > > dafna's patches built on top ?
> > >
> > > Or should patch 1/3 and 3/3 of this series be on top of Dafna's v4 ?
> > >
> > > (It might be noteworthy to say that Kaaira has reported successful
> > > multiple stream operation from /this/ series and her development branch
> > > on libcamera).
> >
> > Dafna's patch seems still under discussion, but I don't want to block progress in Vimc either.
> >
> > So I was wondering if we can move forward with Vimc support for multistreaming,
> > without considering Dafna's patchset, and we can do the clean up later once we solve that.
> >
> > What do you think?
>
> I agree with supporting multiple streams with VIMC with this patchset,
> and then we can refactor the counters for s_stream in VIMC later (over
> this series) if dafna includes them in subsequent version of her patchset.

I also think that adding support in the code will take much longer and should not
stop us from supporting vimc independently.

Thanks,
Dafna

> > Regards,
> > Helen
> >
> > > > > 1.  https://lore.kernel.org/linux-media/20200522075522.6190-1-dafna.hirschfeld@xxxxxxxxxxxxx/
> > > > >
> > > > > > Changes since v1:
> > > > > > 	- All three patches rebased on latest media-tree.
> > > > > > 	Patch 3:
> > > > > > 	- Search for an entity with a non-NULL pipe instead of searching
> > > > > > 	  for sensor. This terminates the search at output itself.
> > > > > >
> > > > > > Kaaira Gupta (3):
> > > > > >    media: vimc: Add usage count to subdevices
> > > > > >    media: vimc: Serialize vimc_streamer_s_stream()
> > > > > >    media: vimc: Join pipeline if one already exists
> > > > > >
> > > > > >   .../media/test-drivers/vimc/vimc-capture.c    | 35 ++++++++++++++++++-
> > > > > >   .../media/test-drivers/vimc/vimc-debayer.c    |  8 +++++
> > > > > >   drivers/media/test-drivers/vimc/vimc-scaler.c |  8 +++++
> > > > > >   drivers/media/test-drivers/vimc/vimc-sensor.c |  9 ++++-
> > > > > >   .../media/test-drivers/vimc/vimc-streamer.c   | 23 +++++++-----
> > > > > >   5 files changed, 73 insertions(+), 10 deletions(-)
> > > > > >
> > > > > > --
> > > > > > 2.17.1
> > > > >
> > > > > --
> > > > > Regards,
> > > > > Niklas SÃderlund