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| -rw-r--r-- | Documentation/userspace-api/sysfs-platform_profile.rst | 42 |
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diff --git a/Documentation/userspace-api/sysfs-platform_profile.rst b/Documentation/userspace-api/sysfs-platform_profile.rst new file mode 100644 index 000000000..c33a71263 --- /dev/null +++ b/Documentation/userspace-api/sysfs-platform_profile.rst @@ -0,0 +1,42 @@ +===================================================================== +Platform Profile Selection (e.g. /sys/firmware/acpi/platform_profile) +===================================================================== + +On modern systems the platform performance, temperature, fan and other +hardware related characteristics are often dynamically configurable. The +platform configuration is often automatically adjusted to the current +conditions by some automatic mechanism (which may very well live outside +the kernel). + +These auto platform adjustment mechanisms often can be configured with +one of several platform profiles, with either a bias towards low power +operation or towards performance. + +The purpose of the platform_profile attribute is to offer a generic sysfs +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. + +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 +about any sub-optimal conditions which are impeding reaching the requested +performance level. + +Since numbers on their own cannot represent the multiple variables that a +profile will adjust (power consumption, heat generation, etc) this API +uses strings to describe the various profiles. To make sure that userspace +gets a consistent experience the sysfs-platform_profile ABI document defines +a fixed set of profile names. Drivers *must* map their internal profile +representation onto this fixed set. + +If there is no good match when mapping then a new profile name may be +added. Drivers which wish to introduce new profile names must: + + 1. Explain why the existing profile names canot be used. + 2. Add the new profile name, along with a clear description of the + expected behaviour, to the sysfs-platform_profile ABI documentation. |