Re: [PATCH v3 01/11] dt-bindings: video-interfaces: Document 'location' property

[Jacopo Mondi <jacopo@jmondi.org>]

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Hi Pavel,
   thanks for input

On Fri, Sep 27, 2019 at 05:27:45PM +0200, Pavel Machek wrote:
> Hi!
>
> > Add the 'location' device property, used to specify a device mounting
> > position. The property is particularly meaningful for mobile devices
> > with a well defined usage orientation.
> >
> > Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> > ---
> >  .../devicetree/bindings/media/video-interfaces.txt    | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/media/video-interfaces.txt b/Documentation/devicetree/bindings/media/video-interfaces.txt
> > index f884ada0bffc..e71b90a29d7a 100644
> > --- a/Documentation/devicetree/bindings/media/video-interfaces.txt
> > +++ b/Documentation/devicetree/bindings/media/video-interfaces.txt
> > @@ -89,6 +89,17 @@ Optional properties
> >    but a number of degrees counter clockwise. Typical values are 0 and 180
> >    (upside down).
> >
> > +- location: The device, typically an image sensor or a flash LED, mounting
> > +  location expressed as a position relative to the usage orientation of the
> > +  system where the device is installed on.
> > +  Possible values are:
> > +  0 - Front. The device is mounted on the front facing side of the system For
> > +  mobile devices such as smartphones, tablets and laptops the front side is the
> > +  user facing side.
>
> I don't think this is nearly enough of description. We have phones
> with displays and cameras at both sides, where both sides can be used
> to operate the system.
>
> We have phone with display spanning both sides -- Mi Max.
>
> https://www.idnes.cz/mobil/telefony/xiaomi-mi-mix-alpha-predstaveni.A190924_105858_telefony_oma
>
> We have Galaxy Fold.
>
> https://www.samsung.com/global/galaxy/galaxy-fold/
>
> What is front side when device can be used in different
> configurations?
>
> Could we instead say that it is "main" vs "selfie" camera?

I'm not sure the intended usage is something that belongs to DT. And
'selfie' implies you have a device side facing you, most like the
'front' one I have defined here.

Not to mention again this devices are all but supported by mainline,
which is just a partial justification as they might be an indication
of a trend.

There is no usable reference place, reference side, reference usage
mode that applies to -all- devices in the world, not one I can think
of.

I still think defining a location property is not blocking any new
extension that accommodate more advanced use cases. It's not like we're
adding a "front-camera" property, it's a "location" and you can expand
its accepted values with "front-when-device-folded" or whatever you
need for future devices.

In the description I mentioned the "usage orientation" to leave room
for possible device-specific details in the definition of the values
accepted by the property.

> > +  location expressed as a position relative to the usage orientation of the
> > +  system where the device is installed on.

99% of devices in the world have a front and a back, as well as they
have a top and a bottom. I still don't see why if a device does not
simply has a front it cannot use something different. The property
definition allows you to do so.

>
> Notebooks usually have just "selfie" camera, tablets often have
> both... DSLRs have just "main" camera.
>
> Best regards,
>
> 									Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html



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