Re: [PATCH v4] platform: x86: Add ACPI driver for ChromeOS

From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"ACPI Devel Maling List" <linux-acpi@vger.kernel.org>,
	"Len Brown" <lenb@kernel.org>,
	"Collabora Kernel ML" <kernel@collabora.com>,
	"Guenter Roeck" <groeck@chromium.org>,
	"Benson Leung" <bleung@chromium.org>,
	"Dmitry Torokhov" <dtor@chromium.org>,
	"Gwendal Grignou" <gwendal@chromium.org>,
	vbendeb@chromium.org, "Andy Shevchenko" <andy@infradead.org>,
	"Ayman Bagabas" <ayman.bagabas@gmail.com>,
	"Benjamin Tissoires" <benjamin.tissoires@redhat.com>,
	"Blaž Hrastnik" <blaz@mxxn.io>,
	"Darren Hart" <dvhart@infradead.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Hans de Goede" <hdegoede@redhat.com>,
	"Jeremy Soller" <jeremy@system76.com>,
	"Mattias Jacobsson" <2pi@mok.nu>,
	"Mauro Carvalho Chehab" <mchehab+samsung@kernel.org>,
	"Rajat Jain" <rajatja@google.com>,
	"Srinivas Pandruvada" <srinivas.pandruvada@linux.intel.com>,
	platform-driver-x86@vger.kernel.org
Subject: Re: [PATCH v4] platform: x86: Add ACPI driver for ChromeOS
Date: Tue, 23 Jun 2020 16:46:58 +0200	[thread overview]
Message-ID: <cb138300-6063-f345-f358-512193a9574c@collabora.com> (raw)
In-Reply-To: <20200606180435.GQ89269@dtor-ws>

Hi Rafael,

On 6/6/20 20:04, Dmitry Torokhov wrote:
> Hi Rafael,
> 
> On Fri, Jun 05, 2020 at 01:17:15PM +0200, Rafael J. Wysocki wrote:
>>
>> First off, GGL0001 is not a valid ACPI device ID, because the GGL prefix is not
>> present in the list at https://uefi.org/acpi_id_list
>>

True, this device ID is not in the ACPI id list, but it is in the legacy PNP id
list at https://uefi.org/pnp_id_list

Even is a legacy one, this device has been here a long time, just that Google
had an out-of-tree patch to support that we would like to upstream.

So, I'm wondering if PNP id's are still valid?

>> There are two ways to address that.  One would be to take the GOOG prefix
>> (present in the list above), append a proper unique number (if I were to
>> guess, I would say that 0001 had been reserved already) to it and then
>> put the resulting device ID into the firmware, to be returned _HID for the
>> device in question (you can add a _CID returning "GGL0001" so it can be
>> found by the old invalid ID at least from the kernel).
> 
> This is not going to happen, as there are devices in the wild with such
> firmware (i.e. Samus - Google Pixel 2 - was shipped in 2015). Even if
> Google were to release updated firmware (which is quite unlikely), it
> does not mean that users who are not using Chrome OS would apply updated
> firmware.
> 
>> The other one would
>> be to properly register the GGL prefix for Google and establish a process for
>> allocating IDs with that prefix internally.
> 
> I think it depends on whether there are more instances of "GGL" prefix.
> I thought we mostly used GOOG for everything.
> 

I only see one instance using GGL, GGL0001 which I think is present on all
ACPI-based Chromebooks, and I'd think that the PNP id GGL is a proper valid
prefix for Google. However is true that then Google mostly used GOOG.

[1]
https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/refs/heads/chromeos-2016.05/src/vendorcode/google/chromeos/acpi/chromeos.asl

Thanks,
 Enric

> Thanks.
> 