linux-kernel - Re: [PATCH] input: mt: Add hovering distance axis

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Date:	Wed, 08 Dec 2010 19:40:29 +0100
From:	Henrik Rydberg <rydberg@...omail.se>
To:	Ping Cheng <pinglinux@...il.com>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Chase Douglas <chase.douglas@...onical.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, Ping Cheng <pingc@...om.com>
Subject: Re: [PATCH] input: mt: Add hovering distance axis

On 12/08/2010 07:20 PM, Ping Cheng wrote:

> On Wed, Dec 8, 2010 at 10:05 AM, Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
>> On Wed, Dec 08, 2010 at 09:46:04AM -0800, Chase Douglas wrote:
>>> On 12/07/2010 12:27 AM, Henrik Rydberg wrote:
>>>> Touch devices capable of hovering, i.e., fingers detected a distance
>>>> from the surface, are not supported by the current input MT
>>>> protocol. This patch adds ABS_MT_DISTANCE, which may be used to
>>>> indicate the distance between the contact and the surface.
>>>
>>> Have you given thought to calling it ABS_MT_Z instead? I have no real
>>> problem with ABS_MT_DISTANCE per se, but ABS_MT_Z is more clearly
>>> defined in my head. If I was new to MT development I may wonder if
>>> ABS_MT_DISTANCE had anything to do with distance between points or some
>>> other object.
>>
>> X/Y/Z imply that we fully engaged the device and it is 3 dimensional.
>> Distance says that we are approaching the device but have not directly
>> engaged it yet.
>>
>> I think ABS_DISTANCE was added at Pings request and ABS_MT_DISTANCE is
>> modeled after ST one. Ping, could you refresh my memory why we needed
>> ABS_DISTANCE?
> 
> ABS_DISTANCE is used in wacom driver as the distance between the tool
> tip and the tablet.


Thanks for the confirmation. While at it, what are the units for the distance,
for instance for the Cintiq?

Henrik
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