linux-kernel - Re: [PATCH 1/2] input: mt: Introduce MT event slots (rev 5)

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Date:	Thu, 10 Jun 2010 10:15:19 -0400
From:	Chase Douglas <chase.douglas@...onical.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Mika Kuoppala <mika.kuoppala@...ia.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	Benjamin Tissoires <tissoire@...a.fr>,
	Stephane Chatty <chatty@...c.fr>,
	Rafi Rubin <rafi@...s.upenn.edu>,
	Michael Poole <mdpoole@...ilus.org>
Subject: Re: [PATCH 1/2] input: mt: Introduce MT event slots (rev 5)

On Sun, 2010-05-23 at 00:30 +0200, Henrik Rydberg wrote:
> With the rapidly increasing number of intelligent multi-contact and
> multi-user devices, the need to send digested, filtered information
> from a set of different sources within the same device is imminent.
> This patch adds the concept of slots to the MT protocol. The slots
> enumerate a set of identified sources, such that all MT events
> can be passed independently and selectively per identified source.
> 
> The protocol works like this: Instead of sending a SYN_MT_REPORT
> event immediately after the contact data, one sends an ABS_MT_SLOT
> event immediately before the contact data. The input core will only
> emit events for slots with modified MT events. It is assumed that
> the same slot is used for the duration of an initiated contact.
> 
> Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
> ---
> Revision 5 incorporates the following changes:
> 	 - Rename the slot event to ABS_MT_SLOT to keep all MT-related events
> 	   in the same namespace.
> 	 - Move the MT slot event list to input.h so that it can be read
> 	   by userspace.
> 
>  drivers/input/input.c |  105 +++++++++++++++++++++++++++++++++++++------------
>  include/linux/input.h |   44 ++++++++++++++++++++
>  2 files changed, 123 insertions(+), 26 deletions(-)

I was wondering what the status of this patch was. I reviewed it and I
think it's a good improvement of the protocol. I think it will help
simplify things in userspace event handling, and should reduce the noise
in evdev. I also like the incremental approach in that it doesn't force
drivers into the new protocol, but makes it available for them when they
can use it.

Acked-by: Chase Douglas <chase.douglas@...onical.com>

Long term, I think it makes the most sense to have a layer inside the
kernel to do software touch tracking and expose all MT data through the
slots protocol instead of it being determined by the capabilities of the
device/driver.

-- Chase

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