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

On Friday 20 February 2015 22:40:38 Mario Limonciello wrote:

On 02/20/2015 03:31 PM, Benjamin Tissoires wrote:

quoted

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

Ah, yeah that makes more sense to me.  And actually the newer
touchpads like the one in the XPS 13 (2015) are microsoft
precision touchpads.  They don't even bother with hid-rmi. 
When in I2C mode the hid-multitouch and i2c-hid driver handle
them sufficiently sans a patch that just hit linux-input to
fix a problem introduced in 3.19 (and 3.18.3).

For clarities sake:
The touchpad in the XPS 13 (2015) will run in I2C or PS2
modes. When_OSI of Windows 2013 is recognized it will be put
into I2C mode.  I know that the current kernel does recognize
Windows 2013 _OSI so by default the touchpad will be in I2C
mode with a new kernel.  Unfortunately this also puts the
sound card into I2S mode which is not yet supported by Linux.
 This is being worked out separately, but currently we are
recommending that customers use acpi_osi="!Windows 2013" to
use the touchpad in PS2 and soundcard in HDA modes.

Obviously this patch isn't applicable when running the
touchpad is running in I2C mode.

Maybe stupid question, but cannot you call that code which put 
sound card into HDA mode from kernel? It could fix problem when 
either sound or touchpad is not working...

-- 
Pali Rohár
pali.rohar@gmail.com