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Date: Wed, 8 Dec 2010 10:20:10 -0800
Message-ID: <AANLkTinKVcc3KA3S_7-vwQWtDuUFZ2LSmjgrCrZXcRw5@mail.gmail.com>
Subject: Re: [PATCH] input: mt: Add hovering distance axis
From: Ping Cheng <pinglinux@gmail.com>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Chase Douglas <chase.douglas@canonical.com>,
        Henrik Rydberg <rydberg@euromail.se>, Jiri Kosina <jkosina@suse.cz>,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ping Cheng <pingc@wacom.com>
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On Wed, Dec 8, 2010 at 10:05 AM, Dmitry Torokhov
<dmitry.torokhov@gmail.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.

Ping
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