linux-kernel - Re: Regression since commit 92bac83

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Message-ID: <56251268.2060203@lwfinger.net>
Date:	Mon, 19 Oct 2015 10:55:20 -0500
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Hans de Goede <hdegoede@...hat.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Pali Rohár <pali.rohar@...il.com>,
	Masaki Ota <masaki.ota@...alps.com>
Cc:	linux-input@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Regression since commit 92bac83

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.

Larry


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