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

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Date:	Fri, 10 Apr 2015 18:07:03 -0500
From:	Mario Limonciello <mario_limonciello@...l.com>
To:	Pali Rohár <pali.rohar@...il.com>
CC:	LKML <linux-kernel@...r.kernel.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>
Subject: Re: [PATCH] Add a quirk for the Dell XPS 13 (2015) when in PS/2 mode.

On 04/10/2015 05:39 PM, Pali Rohár wrote:
> On Wednesday 25 February 2015 21:45:22 Pali Rohár wrote:
> Hello Mario,
> have you patched synaptics driver with some resetafter parameter?
> And have some team in dell found reason for invalid packets?
>
Hi Pali,

The reason was found for the invalid packets in PS2 mode, but I can't go into the details about it publicly.

I think it's better to not bother including my proposed solution, however.  The vector of users in PS2 mode should be very small now.
Here's why:
With no kernel command line options applied the touchpad will run in I2C mode with the current kernel.  The only reason that users were being exposed to the PS2 mode was if they ran with the kernel command line option acpi_osi="!Windows 2013".  This was required with BIOS A01 due to the problem with I2S audio.  This I2S audio problem has been resolved for BIOS A02 and BIOS A03.  With no options applied on the kernel command line the system will run in I2C touchpad and HDA audio.
All new machines will be coming with A03 or later.  Users with earlier versions have been advised to upgrade to fix this among other issues.

The HDA audio will work correctly for output with 4.0.  It will work properly for input when these two patches are applied (which will land in 4.1)

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/?h=for-next&id=e1e62b98ebddc3234f3259019d3236f66fc667f8

and

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/?h=for-next&id=f3b703326541d0c1ce85f5e570f6d2b6bd4296ec

If the patch to disambiguate the value of _REV() lands in 4.1 the audio will begin to operate fully in I2S mode and the necessary support will be included in 4.1 as well.

So with all those factors I feel that it's a very low risk that users will end up in PS2 mode with the current development focus kernels.

Thanks,
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