linux-kernel - Re: [PATCH 4.0 REGRESSION FIX] alps: Fix left touchpad button getting stuck when using it with trackpoint

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Message-ID: <20150412230023.GC15638@dtor-ws>
Date:	Sun, 12 Apr 2015 16:00:23 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Hans de Goede <hdegoede@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Hans de Bruin <jmdebruin@...net.nl>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4.0 REGRESSION FIX] alps: Fix left touchpad button
 getting stuck when using it with trackpoint

On Wed, Apr 08, 2015 at 10:26:36PM +0200, Pali Rohár wrote:
> On Wednesday 08 April 2015 17:38:52 Hans de Goede wrote:
> > When the left touchpad button gets pressed, and then the
> > trackpoint is moved, and then the button is released, the
> > following happens:
> > 
> > 1) touchpad packet is received, touchpad evdev node reports
> > BTN_LEFT 1 2) pointingstick packet is received, the hw will
> > report a BTN_LEFT 1 in this packet because when the
> > trackstick is active it communicates the combined touchpad +
> > pointingstick buttons in the trackstick packet, since
> > alps_report_bare_ps2_packet passes NULL (*) for the dev2
> > parameter to alps_report_buttons the combining is not
> > detected and the pointingstick evdev node will also report
> > BTN_LEFT 1
> > 3) on release of the button a pointingstick packet with
> > BTN_LEFT 0 is received, and the pointingstick evdev node will
> > report BTN_LEFT 0
> > 
> > Note how because of the passing as NULL for dev2 the touchpad
> > evdev node will never send BTN_LEFT 0 in this scenario
> > leading to a stuck mouse button.
> > 
> > This is a regression in 4.0 introduced by commit 04aae283ba6a8
> > ("Input: ALPS - do not mix trackstick and external PS/2 mouse
> > data")
> > 
> > This commit fixes this by passing in the touchpad evdev as
> > dev2 parameter when calling alps_report_buttons for the
> > pointingstick on alps v2 devices, so that alps_report_buttons
> > correctly detect that we're already reporting the button as
> > pressed via the touchpad evdev node, and will also send the
> > release event there.
> > 
> > Reported-by: Hans de Bruin <jmdebruin@...net.nl>
> > Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> 
> Patch looks good to me, so
> 
> Acked-by: Pali Rohár <pali.rohar@...il.com>
> 
> As this is regression in 4.0 (which was not in 3.19), I'm also 
> for fixing it. But decision is of course on maintainers...

Doh! Missed the 4.0 so had to tag it for stable.

-- 
Dmitry
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