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

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Message-ID: <20200728113959.GA6350@kaaira-HP-Pavilion-Notebook>
Date:   Tue, 28 Jul 2020 17:09:59 +0530
From:   Kaaira Gupta <kgupta@...iitr.ac.in>
To:     Helen Koike <helen.koike@...labora.com>
Cc:     kieran.bingham@...asonboard.com,
        Kaaira Gupta <kgupta@...iitr.ac.in>,
        Niklas Söderlund 
        <niklas.soderlund@...natech.se>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dafna Hirschfeld <dafna.hirschfeld@...labora.com>
Subject: Re: [PATCH v2 0/3] media: vimc: Allow multiple capture devices to
 use the same sensor

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 Söderlund 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'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.

> 
> Regards,
> Helen
> 
> > 
> > 
> >>> 1.  https://lore.kernel.org/linux-media/20200522075522.6190-1-dafna.hirschfeld@collabora.com/
> >>>
> >>>>
> >>>> 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 Söderlund
> >