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Date:   Wed, 12 Apr 2023 15:05:46 +0300
From:   Sakari Ailus <sakari.ailus@linux.intel.com>
To:     Michael Riesch <michael.riesch@wolfvision.net>
Cc:     Dave Stevenson <dave.stevenson@raspberrypi.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Michael Riesch via B4 Relay 
        <devnull+michael.riesch.wolfvision.net@kernel.org>,
        linux-kernel@vger.kernel.org,
        Matthias Fend <Matthias.Fend@wolfvision.net>,
        libcamera-devel@lists.libcamera.org, linux-media@vger.kernel.org,
        hverkuil@xs4all.nl
Subject: Re: [libcamera-devel] [PATCH RFC 1/4] media: v4l2-ctrls: add lens
 group status controls for zoom and focus
Message-ID: <ZDaemghP0HQSw3Fo@kekkonen.localdomain>
References: <20230406-feature-controls-lens-v1-0-543189a680de@wolfvision.net>
 <20230406-feature-controls-lens-v1-1-543189a680de@wolfvision.net>
 <CAPY8ntArOOqPQzvkJrQEyuVFfb6j8x6WODTMHOn1qHPU588mbQ@mail.gmail.com>
 <0f1baf5e-2ff6-e10b-5c3e-0a82c71d0ce6@wolfvision.net>
 <CAPY8ntAjBEFfeV6nnQs34Y22QM-irT13ALDv4ksP8AYK=jWsKg@mail.gmail.com>
 <3ab7bfc4-aaae-2e39-b420-40ad8d71dda4@wolfvision.net>
 <ZDaa+qhoZxZ5ymxL@kekkonen.localdomain>
 <8fe5c9c5-6eb0-86ae-9e5d-fbaa72be25fe@wolfvision.net>
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Hi Michael,

On Wed, Apr 12, 2023 at 01:57:36PM +0200, Michael Riesch wrote:
> Hi Sakari,
> 
> On 4/12/23 13:50, Sakari Ailus wrote:
> > Hi Michael,
> > 
> > On Wed, Apr 12, 2023 at 10:00:26AM +0200, Michael Riesch wrote:
> >>  - Different controls: If moving = (V4L2_CID_FOCUS_ABSOLUTE == current),
> >>    then what happens if the application performs a
> >>    V4L2_CID_FOCUS_RELATIVE with -3? current should reach 39,
> >>    V4L2_CID_FOCUS_ABSOLUTE is still at 42, the lens is still moving from
> >>    the application's point of view.
> > 
> > Would there be a reason to implement both of these controls in a single
> > driver? AFAIU, the relative one should be used if there absolute value
> > isn't known to the driver.
> 
> Probably not, but on the other hand there is nothing the prevents a
> driver developer from doing so, right? Point is that should there be a
> driver which does implement both controls, we are in trouble AFAIU.

I think the documentation should be improved in this regard.

Also cc Hans.

-- 
Regards,

Sakari Ailus