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
[off-list ref] wrote:

On 02/20/2015 02:41 PM, Pali Rohár wrote:

quoted

[snipped]

quoted

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