linux-kernel - Re: Reporting screen/laptop orientation data to userspace

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Message-ID: <1307116529.2669.130.camel@novo.hadess.net>
Date:	Fri, 03 Jun 2011 16:55:28 +0100
From:	Bastien Nocera <hadess@...ess.net>
To:	Alberto Mardegan <mardy@...rs.sourceforge.net>
Cc:	linux-kernel@...r.kernel.org,
	"Javier S. Pedro" <maemo@...ispedro.com>,
	linux-input@...r.kernel.org
Subject: Re: Reporting screen/laptop orientation data to userspace

On Sun, 2011-05-29 at 10:49 +0300, Alberto Mardegan wrote:
> Hi all,
>   the WMI interfaces in some Lenovo Ideapad laptops provide notification
> callbacks when the laptop orientation changes, reporting 4 different
> values defining the new orientation.
> 
> I'd like to extend the ideapad-laptop driver with this information; but
> how should it be reported to userspace? I initially thought of the input
> subsystem, but I cannot find any suitable event codes; then I would
> probably export it as a device under /sys, or are there better options?
> 
> Are there other devices which provide coarse orientation data to
> userspace, which I might want to use as a reference?
> I guess that at least some display screens have this feature.

Do you also have a discrete accelerometer with that? Or you only ever
get notification through there?

If there is a discrete accelerometer, I'd drop the extra metadata, and
send an event through udev, and expect user-space to read from the
accelerometer instead.

If there isn't a discrete accelerometer, create a fake one, with some
hardcoded data based on the actual orientation of the device.

The accelerometer (whether real or fake) should show 3 axis (X/Y/Z).

As soon as it's seen some testing, I'll be showing the work I did for
GNOME support for automatic rotation based on orientation.

Cheers

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