linux-kernel - Re: [PATCH 0/3] Add support for hidden choices to platform

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Message-Id: <fcf58c76-2c0b-4892-96aa-c9b5b35c3e68@app.fastmail.com>
Date: Fri, 28 Feb 2025 14:39:35 -0500
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Mario Limonciello" <superm1@...nel.org>,
 "Shyam Sundar S K" <Shyam-sundar.S-k@....com>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 "Hans de Goede" <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 "Luke D . Jones" <luke@...nes.dev>
Cc: 
 "platform-driver-x86@...r.kernel.org" <platform-driver-x86@...r.kernel.org>,
 "open list" <linux-kernel@...r.kernel.org>,
 "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
 "Derek J . Clark" <derekjohn.clark@...il.com>,
 "Antheas Kapenekakis" <lkml@...heas.dev>, me@...egospodneti.ch,
 "Denis Benato" <benato.denis96@...il.com>,
 "Limonciello, Mario" <mario.limonciello@....com>
Subject: Re: [PATCH 0/3] Add support for hidden choices to platform_profile

Hi Mario,

On Fri, Feb 28, 2025, at 12:01 PM, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@....com>
>
> When two drivers provide platform profile handlers but use different
> strings to mean (essentially) the same thing the legacy interface won't
> export them because it only shows profiles common to multiple drivers.
>
> This causes an unexpected behavior to people who have upgraded from an
> earlier kernel because if multiple drivers have bound platform profile
> handlers they might not be able to access profiles they were expecting.
>
> Introduce a concept of a "hidden choice" that drivers can register and
> the platform profile handler code will utilize when using the legacy
> interface.
>
> There have been some other attempts at solving this issue in other ways.
> This serves as an alternative to those attempts.
>
> Link: 
> https://lore.kernel.org/platform-driver-x86/e64b771e-3255-42ad-9257-5b8fc6c24ac9@gmx.de/T/#t
> Link: 
> https://lore.kernel.org/platform-driver-x86/CAGwozwF-WVEgiAbWbRCiUaXf=BVa3KqmMJfs06trdMQHpTGmjQ@mail.gmail.com/T/#m2f3929e2d4f73cc0eedd14738170dad45232fd18
> Cc: Antheas Kapenekakis <lkml@...heas.dev>
> Cc: "Luke D. Jones" <luke@...nes.dev>
>
> Mario Limonciello (3):
>   ACPI: platform_profile: Add support for hidden choices
>   platform/x86/amd: pmf: Add 'quiet' to hidden choices
>   platform/x86/amd: pmf: Add balanced-performance to hidden choices
>
>  drivers/acpi/platform_profile.c    | 94 +++++++++++++++++++++++-------
>  drivers/platform/x86/amd/pmf/sps.c | 11 ++++
>  include/linux/platform_profile.h   |  3 +
>  3 files changed, 87 insertions(+), 21 deletions(-)
>
> -- 
> 2.43.0

The patches are all good - but my question is do we really need the whole hidden implementation bit?

If the options are not hidden, and someone chooses quiet or balanced-performance for the amd-pmf driver - does it really matter that it's going to do the same as low-power or performance?

So, same feedback as I had for Antheas's patches. I understand why this is being proposed but for me it is making things unnecessarily complicated.

My personal vote remains that the amd_pmf driver carries the superset to keep everyone happy (sorry - it sucks to be the CPU vendor that has to play nice with everyone).

Mark