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TOMOYO Linux Cross Reference
Linux/Documentation/userspace-api/sysfs-platform_profile.rst

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  1 =====================================================================
  2 Platform Profile Selection (e.g. /sys/firmware/acpi/platform_profile)
  3 =====================================================================
  4 
  5 On modern systems the platform performance, temperature, fan and other
  6 hardware related characteristics are often dynamically configurable. The
  7 platform configuration is often automatically adjusted to the current
  8 conditions by some automatic mechanism (which may very well live outside
  9 the kernel).
 10 
 11 These auto platform adjustment mechanisms often can be configured with
 12 one of several platform profiles, with either a bias towards low power
 13 operation or towards performance.
 14 
 15 The purpose of the platform_profile attribute is to offer a generic sysfs
 16 API for selecting the platform profile of these automatic mechanisms.
 17 
 18 Note that this API is only for selecting the platform profile, it is
 19 NOT a goal of this API to allow monitoring the resulting performance
 20 characteristics. Monitoring performance is best done with device/vendor
 21 specific tools such as e.g. turbostat.
 22 
 23 Specifically when selecting a high performance profile the actual achieved
 24 performance may be limited by various factors such as: the heat generated
 25 by other components, room temperature, free air flow at the bottom of a
 26 laptop, etc. It is explicitly NOT a goal of this API to let userspace know
 27 about any sub-optimal conditions which are impeding reaching the requested
 28 performance level.
 29 
 30 Since numbers on their own cannot represent the multiple variables that a
 31 profile will adjust (power consumption, heat generation, etc) this API
 32 uses strings to describe the various profiles. To make sure that userspace
 33 gets a consistent experience the sysfs-platform_profile ABI document defines
 34 a fixed set of profile names. Drivers *must* map their internal profile
 35 representation onto this fixed set.
 36 
 37 If there is no good match when mapping then a new profile name may be
 38 added. Drivers which wish to introduce new profile names must:
 39 
 40  1. Explain why the existing profile names cannot be used.
 41  2. Add the new profile name, along with a clear description of the
 42     expected behaviour, to the sysfs-platform_profile ABI documentation.

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