linux-kernel - Re: [PATCH 2/2] input: mt: Document the MT event slot protocol (rev2)

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Message-ID: <4BFAD12D.1000607@euromail.se>
Date:	Mon, 24 May 2010 21:19:09 +0200
From:	Henrik Rydberg <rydberg@...omail.se>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Ping Cheng <pinglinux@...il.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Mika Kuoppala <mika.kuoppala@...ia.com>,
	Benjamin Tissoires <tissoire@...a.fr>,
	Stephane Chatty <chatty@...c.fr>,
	Rafi Rubin <rafi@...s.upenn.edu>,
	Michael Poole <mdpoole@...ilus.org>
Subject: Re: [PATCH 2/2] input: mt: Document the MT event slot protocol (rev2)

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
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