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References: <20231020-uvc-event-v1-1-3baa0e9f6952@chromium.org>
 <20231106103925.GA19272@pendragon.ideasonboard.com> <20231106104245.GB19272@pendragon.ideasonboard.com>
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From:   Ricardo Ribalda <ribalda@chromium.org>
Date:   Mon, 6 Nov 2023 11:51:06 +0100
Message-ID: <CANiDSCsnrb5a3XTnHRrUjttcV6aAw7yC6RtUApvsK5CBhFGJyQ@mail.gmail.com>
Subject: Re: [PATCH] media: uvcvideo: Implement V4L2_EVENT_FRAME_SYNC
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Esker Wong <esker@chromium.org>
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Hi Laurent

On Mon, 6 Nov 2023 at 11:42, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Mon, Nov 06, 2023 at 12:39:26PM +0200, Laurent Pinchart wrote:
> > On Fri, Oct 20, 2023 at 06:41:45AM +0000, Ricardo Ribalda wrote:
> > > Add support for the frame_sync event, so user-space can become aware
> > > earlier of new frames.
> > >
> > > Suggested-by: Esker Wong <esker@chromium.org>
> > > Tested-by: Esker Wong <esker@chromium.org>
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > > We have measured a latency of around 30msecs between frame sync
> > > and dqbuf.
> >
> > Not surprising, especially for large resolutions. I'm curious though,
> > what do you use this event for ?

I think Esker is using it to get more accurate power measurements of
the camera stack.

> > It's easy to miss the ++ there when reading the code, would the
> > following be more readable ?

Actually that was my original code, but I thought you would like this better :)

Thanks for the review, a v2 is on its way.

> --
> Regards,
>
> Laurent Pinchart


-- 
Ricardo Ribalda