linux-kernel - Re: [PATCH] media: uvcvideo: Implement V4L2_EVENT_FRAME

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Message-ID: <20231106105941.GB16995@pendragon.ideasonboard.com>
Date:   Mon, 6 Nov 2023 12:59:41 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Esker Wong <esker@...omium.org>
Subject: Re: [PATCH] media: uvcvideo: Implement V4L2_EVENT_FRAME_SYNC

On Mon, Nov 06, 2023 at 11:51:06AM +0100, Ricardo Ribalda wrote:
> On Mon, 6 Nov 2023 at 11:42, Laurent Pinchart 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@...omium.org>
> > > > Tested-by: Esker Wong <esker@...omium.org>
> > > > Signed-off-by: Ricardo Ribalda <ribalda@...omium.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.

Esker, would you be able to provide more information ?

> > > 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.

Thank you.

-- 
Regards,

Laurent Pinchart