linux-kernel - Re: [PATCH] Add a quirk for the Dell XPS 13 (2015) when in PS/2 mode.

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Message-ID: <CAN+gG=F6TyoOb=nNeBAsdh7RrEUWoeJtznTY4YNmr3UGxQ1Hjg@mail.gmail.com>
Date:	Fri, 20 Feb 2015 16:31:23 -0500
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Mario Limonciello <mario_limonciello@...l.com>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	Rob <robr.bensson@...il.com>
Subject: Re: [PATCH] Add a quirk for the Dell XPS 13 (2015) when in PS/2 mode.

On Fri, Feb 20, 2015 at 4:21 PM, Mario Limonciello
<mario_limonciello@...l.com> wrote:
>
> On 02/20/2015 02:41 PM, Pali Rohár wrote:
>>
[snipped]
>
>> There is problem with some synaptics touchpad on some laptops
>> (probably not dell). Windows driver loads own firmware into
>> synaptics touchpad which use different protocol (as original
>> firmware in touchpad). And that loaded firmware is active until
>> laptop is not shut down. When you reboot from Windows to Linux
>> then linux kernel driver refuse to identify & use touchpad
>> because it does not support that new firmware loaded by
>> Windows... I do not know lot of about this problem, I just heard
>> about it from other people. I did not see any laptop "in action".
>>
> Ah, so it's a special interface that's implemented in the Synaptics Windows
> driver.  As described above this sounds like a stop gap type solution to
> resolve a field problem until the firmware can be implemented into
> manufactured parts.  I'd suspect that people who purchased the same model of
> this computer later might run into problems without warm booting as the
> firmware got updated into the manufacturer's factory.
>
>

What is most likely happening is that the synaptics driver switches
the touchpad into the i2c/hid protocol. And yes Synaptics told us that
only a reset re-enables the touchpad in the PS/2 mode.
Kernels 3.11 and later know how to deal with this mode (through
hid-rmi), so we should not see these problems in the future unless
hid-rmi is not compiled in the running kernel.

Fortunately, we can deal with the Dell/Synaptics touchpads, the Lenovo
ones are using SMBus, and we have never been able to talk to the
devices with SMBus :(

Cheers,
Benjamin
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