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

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Message-ID: <cb138300-6063-f345-f358-512193a9574c@collabora.com>
Date:   Tue, 23 Jun 2020 16:46:58 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Len Brown <lenb@...nel.org>,
        Collabora Kernel ML <kernel@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Dmitry Torokhov <dtor@...omium.org>,
        Gwendal Grignou <gwendal@...omium.org>, vbendeb@...omium.org,
        Andy Shevchenko <andy@...radead.org>,
        Ayman Bagabas <ayman.bagabas@...il.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Blaž Hrastnik <blaz@...n.io>,
        Darren Hart <dvhart@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Jeremy Soller <jeremy@...tem76.com>,
        Mattias Jacobsson <2pi@....nu>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Rajat Jain <rajatja@...gle.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v4] platform: x86: Add ACPI driver for ChromeOS

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.
>