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

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Message-ID: <20190902082739.GE15850@amd>
Date:   Mon, 2 Sep 2019 10:27:39 +0200
From:   Pavel Machek <pavel@....cz>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
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 2019-09-02 11:19:42, Laurent Pinchart wrote:
> 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.

Well, the mechanism is there just to rotate the camera.

Anyway, that phone is probably nowhere close to having mainline
support, so...

									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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