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Message-ID: <8fe5c9c5-6eb0-86ae-9e5d-fbaa72be25fe@wolfvision.net>
Date:   Wed, 12 Apr 2023 13:57:36 +0200
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Subject: Re: [libcamera-devel] [PATCH RFC 1/4] media: v4l2-ctrls: add lens
 group status controls for zoom and focus
Content-Language: en-US
To:     Sakari Ailus <sakari.ailus@linux.intel.com>
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
References: <20230406-feature-controls-lens-v1-0-543189a680de@wolfvision.net>
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From:   Michael Riesch <michael.riesch@wolfvision.net>
Organization: WolfVision GmbH
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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.

Best regards,
Michael