linux-kernel - Re: [PATCH 0/4] Input: ABS2 and friends

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Date:	Wed, 18 Dec 2013 09:12:45 +0100
From:	David Herrmann <dh.herrmann@...il.com>
To:	Simon Wood <simon@...gewell.org>
Cc:	"open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Benjamin Tissoires <benjamin.tissoires@...il.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	Antonio Ospite <ospite@...denti.unina.it>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Input Tools <input-tools@...ts.freedesktop.org>
Subject: Re: [PATCH 0/4] Input: ABS2 and friends

Hi

On Tue, Dec 17, 2013 at 10:28 PM,  <simon@...gewell.org> wrote:
>> Hi
>>
>> This implements the recently discussed ABS2 API. It's working fine on my
>> machine with libevdev. Comments welcome!
>
> Just looking at the documentation file, I have a couple of suggestions.
>
> 1). Make a note on the direction of gravity wrt the example image. Ie what
> which axis/value will be positive with the device laid flat/stationary on
> a desk. Might just prevent some confusion later.

Yepp, can add that to the Accelerometer section.

> 2). Calibration, Accels and Gyros are noisy in different ways. Gyros tend
> to be wrong in the long term, giving some consistant bias which should be
> calibrated out. Accels are noisy in the short term, but generally right
> over a long period.

I'm not entirely sure where to put calibration/normalization. Letting
user-space deal with that should simplify things a lot. We could even
add it to libevdev. Comments welcome..

> Am I correct that the event framework will provide time-stamping of data,
> thus making computation of relative movements possible.

Yes, part of the evdev API.

Thanks
David
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