linux-kernel - Re: Regression since commit 92bac83

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Date:	Tue, 20 Oct 2015 09:22:23 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Larry Finger <Larry.Finger@...inger.net>,
	Hans de Goede <hdegoede@...hat.com>,
	Masaki Ota <masaki.ota@...alps.com>,
	linux-input@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Regression since commit 92bac83

On Monday 19 October 2015 09:51:28 Dmitry Torokhov wrote:
> On Mon, Oct 19, 2015 at 10:55:20AM -0500, Larry Finger wrote:
> > On 10/19/2015 03:08 AM, Hans de Goede wrote:
> > >Hi,
> > >
> > >On 19-10-15 01:59, Larry Finger wrote:
> > >>Hi,
> > >>
> > >>I recently upgraded the kernel in a Dell Latitude D600 and found that the
> > >>touchpad clicks failed. The problem was bisected to commit
> > >>92bac83dd79e60e65c475222e41a992a70434beb ("Input: alps - non interleaved V2
> > >>dualpoint has separate stick button bits"). The laptop has a combination
> > >>touchpad and control stick. For this device, the following values are found:
> > >>
> > >>priv->protoversion is 0x200 (ALPS_PROTO_V2)
> > >>priv->flags is 0x6 (ALPS_DUALPOINT | ALPS_PASS)
> > >>
> > >>As a result, the new code added in this patch is executed, and left, right,
> > >>and middle are updated. Once this code is introduced, a left click causes some
> > >>event as it will wake a sleeping screen, but not select any windows or do
> > >>anything useful.
> > >>
> > >>Please advise on what information would be needed to help debug this problem.
> > >
> > >Can you build a recent upstream kernel from source, and when building it
> > >comment out these lines in drivers/input/mouse/alps.c, around lines 2555 - 2556
> > >
> > >         if (dmi_name_in_vendors("Dell"))
> > >                 priv->flags |= ALPS_DELL;
> > >
> > >That should fix things, if that fixes things we need to rename the flag
> > >and move to a list of dmi-matched models (rather then vendor) where the new
> > >behavior
> > >introduced by the patch causing you problems is actually necessary.
> > >
> > >Step 1 is confirming that not setting the flag fixes things for you,
> > >if you can get back to us confirming that, then I'll whip up a patch
> > >to switch to model matching (which is not ideal, but seems to be
> > >necessary).
> > 
> > Thanks for the quick response. Removing the two lines mentioned
> > above restored correct touchpad operation with kernel 4.2.0. It
> > seems that the Latitude D600 is different than other Dell models.
> 
> I wonder if we should not revert all these patches splitting what once
> was one relative input device into separate trackstick/external mouse.
> They seem to cause a lot of troubles for little benefit. Pali?
> 
> Thanks.
> 

Hi Dmitry! I think that this bug is not related to my separation
patches, but rather to approach which is trying to fix some obscure bug
on some Dell machines...

-- 
Pali Rohár
pali.rohar@...il.com
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