linux-kernel - Re: [PATCH v6 22/22] Documentation: Add documentation about class interface for platform profiles

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Message-ID: <229772cf-9671-429f-bb2d-70f1f4e56172@gmx.de>
Date: Sun, 17 Nov 2024 20:34:33 +0100
From: Armin Wolf <W_Armin@....de>
To: Mario Limonciello <mario.limonciello@....com>,
 Hans de Goede <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 Maximilian Luz <luzmaximilian@...il.com>, Lee Chun-Yi <jlee@...e.com>,
 Shyam Sundar S K <Shyam-sundar.S-k@....com>,
 Corentin Chary <corentin.chary@...il.com>, "Luke D . Jones"
 <luke@...nes.dev>, Ike Panhc <ike.pan@...onical.com>,
 Henrique de Moraes Holschuh <hmh@....eng.br>,
 Alexis Belmonte <alexbelm48@...il.com>,
 Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
 Ai Chao <aichao@...inos.cn>, Gergo Koteles <soyer@....hu>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:ACPI" <linux-acpi@...r.kernel.org>,
 "open list:MICROSOFT SURFACE PLATFORM PROFILE DRIVER"
 <platform-driver-x86@...r.kernel.org>,
 "open list:THINKPAD ACPI EXTRAS DRIVER"
 <ibm-acpi-devel@...ts.sourceforge.net>,
 Mark Pearson <mpearson-lenovo@...ebb.ca>,
 Matthew Schwartz <matthew.schwartz@...ux.dev>
Subject: Re: [PATCH v6 22/22] Documentation: Add documentation about class
 interface for platform profiles

Am 09.11.24 um 05:41 schrieb Mario Limonciello:

> The class interface allows changing multiple platform profiles on a system
> to different values. The semantics of it are similar to the legacy
> interface.
>
> Tested-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> v5:
>   * Fix some typos
> ---
>   .../ABI/testing/sysfs-platform_profile        |  5 ++++
>   .../userspace-api/sysfs-platform_profile.rst  | 28 +++++++++++++++++++
>   2 files changed, 33 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-platform_profile b/Documentation/ABI/testing/sysfs-platform_profile
> index baf1d125f9f83..125324ab53a96 100644
> --- a/Documentation/ABI/testing/sysfs-platform_profile
> +++ b/Documentation/ABI/testing/sysfs-platform_profile
> @@ -33,3 +33,8 @@ Description:	Reading this file gives the current selected profile for this
>   		source such as e.g. a hotkey triggered profile change handled
>   		either directly by the embedded-controller or fully handled
>   		inside the kernel.
> +
> +		This file may also emit the string 'custom' to indicate
> +		that multiple platform profiles drivers are in use but
> +		have different values.  This string can not be written to
> +		this interface and is solely for informational purposes.
> diff --git a/Documentation/userspace-api/sysfs-platform_profile.rst b/Documentation/userspace-api/sysfs-platform_profile.rst
> index 4fccde2e45639..b746c30432753 100644
> --- a/Documentation/userspace-api/sysfs-platform_profile.rst
> +++ b/Documentation/userspace-api/sysfs-platform_profile.rst
> @@ -40,3 +40,31 @@ added. Drivers which wish to introduce new profile names must:
>    1. Explain why the existing profile names cannot be used.
>    2. Add the new profile name, along with a clear description of the
>       expected behaviour, to the sysfs-platform_profile ABI documentation.
> +
> +Multiple driver support
> +=======================
> +When multiple drivers on a system advertise a platform profile handler, the
> +platform profile handler core will only advertise the profiles that are
> +common between all drivers to the ``/sys/firmware/acpi`` interfaces.
> +
> +This is to ensure there is no ambiguity on what the profile names mean when
> +all handlers don't support a profile.
> +
> +Individual drivers will register a 'platform_profile' class device that has
> +similar semantics as the ``/sys/firmware/acpi/platform_profile`` interface.
> +

Please add a short description of the 'name' attribute of the class device.

With that being addressed:

Reviewed-by: Armin Wolf <W_Armin@....de>

> +To discover available profiles from the class interface the user can read the
> +``choices`` attribute.
> +
> +If a user wants to select a profile for a specific driver, they can do so
> +by writing to the ``profile`` attribute of the driver's class device.
> +
> +This will allow users to set different profiles for different drivers on the
> +same system. If the selected profile by individual drivers differs the
> +platform profile handler core will display the profile 'custom' to indicate
> +that the profiles are not the same.
> +
> +While the ``platform_profile`` attribute has the value ``custom``, writing a
> +common profile from ``platform_profile_choices`` to the platform_profile
> +attribute of the platform profile handler core will set the profile for all
> +drivers.