linux-kernel - Re: [RFC 2/5] media: v4l2-ctrl: Document V4L2_CID

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Message-ID: <20190902081942.GE4777@pendragon.ideasonboard.com>
Date:   Mon, 2 Sep 2019 11:19:42 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "open list:MEDIA INPUT INFRASTRUCTURE (V4L/DVB)" 
        <linux-media@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 2/5] media: v4l2-ctrl: Document V4L2_CID_LOCATION

On Mon, Sep 02, 2019 at 10:06:57AM +0200, Pavel Machek wrote:
> >>> Single integer. It's read-only, so it just reports the location.
> >>> 
> >>> It would be different if this was a writable control: then you need to
> >>> know which locations are possible to set, and that requires a menu type.
> >>> 
> >>> But it doesn't make sense to set the location from software. However, the
> >>> location might change as a result of other changes: e.g. if the camera
> >>> has motor control of the tilt and the tilt changes from forward facing to
> >>> downward facing, then the driver might change the location from FRONT
> >>> to DOWN. A convoluted example perhaps, but this is just brainstorming.
> >> 
> >> There are phones with exactly such camera setup. And yes, it makes
> >> sense to be writable in that case, as software can move the camera in
> >> such case.
> > 
> > Out of curiosity, what phones are those ?
> 
> This one:
> 
> https://www.samsung.com/global/galaxy/galaxy-a80/

Interesting device. I'm not sure we should control that through a
location control though, as it seems there's more than the rotation of
the camera involved. In any case I wouldn't care about it for now, and
turn the location control from read-only to read-write later if needed.
We need more information and more thought to support that use case.

-- 
Regards,

Laurent Pinchart