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Date: Mon, 24 May 2010 21:19:09 +0200
From: Henrik Rydberg <rydberg@euromail.se>
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To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
CC: Ping Cheng <pinglinux@gmail.com>,
       Peter Hutterer <peter.hutterer@who-t.net>,
       Andrew Morton <akpm@linux-foundation.org>, linux-input@vger.kernel.org,
       linux-kernel@vger.kernel.org, Mika Kuoppala <mika.kuoppala@nokia.com>,
       Benjamin Tissoires <tissoire@cena.fr>, Stephane Chatty <chatty@enac.fr>,
       Rafi Rubin <rafi@seas.upenn.edu>, Michael Poole <mdpoole@troilus.org>
Subject: Re: [PATCH 2/2] input: mt: Document the MT event slot protocol (rev2)
References: <1274213429-22667-1-git-send-email-rydberg@euromail.se> <20100524155901.GB3182@core.coreip.homeip.net> <AANLkTin9ahtqL7jrUP4C0zF9-P3rUg7ktN93-hcqdDnj@mail.gmail.com> <201005241021.02731.dmitry.torokhov@gmail.com> <4BFABBD0.9020202@euromail.se> <20100524180411.GA6033@core.coreip.homeip.net>
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Dmitry Torokhov wrote:
> On Mon, May 24, 2010 at 07:48:00PM +0200, Henrik Rydberg wrote:
>> Dmitry Torokhov wrote:
>> [...]
>>>>>> I think we need to add an ioctl to enable user land driver/client to
>>>>>> signal the kernel driver to send all events without filtering, just
>>>>>> once. Hot-plugged devices and X driver starts after user has contacted
>>>>>> with the device are two examples that the client would miss filtered
>>>>>> events.
>>>>>>
>>>>>> Dmitry, do you think it is a valid suggestion?
>>>>> What about using EVIOCGKEY/EVIOCGSW/EVIOCGABS?
>>>> Those EVIOCs only give us the static values (max/min/supported keys,
>>>> etc.).  We need their dynamic input data here, the actual x, y,
>>>> button, pressure, etc. Am I missing something about those EVIOs?
>>>>
>>> Yes you are ;) Supported events are reported via EVIOCGBIT, EVIOCGKEY and
>>> EVIOCGSW will return current state of keys/switches. As far as EVIOCGABS
>>> goes, it also returns, besides min/max/etc, last reported _values_ of the
>>> ABS_* events.
>>>
>> Ping is not alone. :-)
>>
>> But it does not work for MT events -- yet.
>>
> 
> Yes, this is true.
> 
> I think the most interesting is the switch data, since they may not change
> at all. The rest is transient and should refresh "fairly quickly".
> 

Still, if one allows EVIOCSABS(ABS_MT_SLOT) to set a slot state in evdev instead
of modifying the input_dev, one could extract all ABS_MT events in sequence via
EVIOCGABS.

Henrik