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