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Diffstat (limited to 'Documentation/userspace-api/sysfs-platform_profile.rst')
| -rw-r--r-- | Documentation/userspace-api/sysfs-platform_profile.rst | 42 |
1 files changed, 40 insertions, 2 deletions
diff --git a/Documentation/userspace-api/sysfs-platform_profile.rst b/Documentation/userspace-api/sysfs-platform_profile.rst index 4fccde2e4563..6613e188242a 100644 --- a/Documentation/userspace-api/sysfs-platform_profile.rst +++ b/Documentation/userspace-api/sysfs-platform_profile.rst @@ -18,9 +18,9 @@ API for selecting the platform profile of these automatic mechanisms. Note that this API is only for selecting the platform profile, it is NOT a goal of this API to allow monitoring the resulting performance characteristics. Monitoring performance is best done with device/vendor -specific tools such as e.g. turbostat. +specific tools, e.g. turbostat. -Specifically when selecting a high performance profile the actual achieved +Specifically, when selecting a high performance profile the actual achieved performance may be limited by various factors such as: the heat generated by other components, room temperature, free air flow at the bottom of a laptop, etc. It is explicitly NOT a goal of this API to let userspace know @@ -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 settings 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. |