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Documentation: Add documentation about class interface for platform profiles

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The class interface allows changing multiple platform profiles on a system
to different values. The semantics of it are similar to the legacy
interface.

Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Tested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20241206031918.1537-23-mario.limonciello@amd.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
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Mario Limonciello 2024-12-05 21:19:18 -06:00 committed by Ilpo Järvinen
parent dd7ba84afa
commit 0056b0852c
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5
Documentation/ABI/testing/sysfs-platform_profile
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@ -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.

38
Documentation/userspace-api/sysfs-platform_profile.rst
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@ -40,3 +40,41 @@ 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.
"Custom" profile support
========================
The platform_profile class also supports profiles advertising a "custom"
profile. This is intended to be set by drivers when the setttings in the
driver have been modified in a way that a standard profile doesn't represent
the current state.
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 which driver is associated with a platform profile handler the
user can read the ``name`` attribute of the class device.
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.