linux-kernel - [PATCH v5 20/20] Documentation: Add documentation about class interface for platform profiles

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Message-ID: <20241107060254.17615-21-mario.limonciello@amd.com>
Date: Thu, 7 Nov 2024 00:02:54 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: 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>,
	Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH v5 20/20] Documentation: Add documentation about class interface for platform profiles

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.
+
+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.
-- 
2.43.0