c1966bd1f0
Correct spelling problems for Documentation/userspace-api/ as reported by codespell. Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: linux-doc@vger.kernel.org Cc: Sean Young <sean@mess.org> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: linux-media@vger.kernel.org Link: https://lore.kernel.org/r/20230129231053.20863-10-rdunlap@infradead.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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43 lines
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=====================================================================
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Platform Profile Selection (e.g. /sys/firmware/acpi/platform_profile)
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=====================================================================
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On modern systems the platform performance, temperature, fan and other
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hardware related characteristics are often dynamically configurable. The
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platform configuration is often automatically adjusted to the current
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conditions by some automatic mechanism (which may very well live outside
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the kernel).
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These auto platform adjustment mechanisms often can be configured with
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one of several platform profiles, with either a bias towards low power
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operation or towards performance.
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The purpose of the platform_profile attribute is to offer a generic sysfs
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API for selecting the platform profile of these automatic mechanisms.
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Note that this API is only for selecting the platform profile, it is
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NOT a goal of this API to allow monitoring the resulting performance
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characteristics. Monitoring performance is best done with device/vendor
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specific tools such as e.g. turbostat.
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Specifically when selecting a high performance profile the actual achieved
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performance may be limited by various factors such as: the heat generated
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by other components, room temperature, free air flow at the bottom of a
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laptop, etc. It is explicitly NOT a goal of this API to let userspace know
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about any sub-optimal conditions which are impeding reaching the requested
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performance level.
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Since numbers on their own cannot represent the multiple variables that a
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profile will adjust (power consumption, heat generation, etc) this API
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uses strings to describe the various profiles. To make sure that userspace
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gets a consistent experience the sysfs-platform_profile ABI document defines
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a fixed set of profile names. Drivers *must* map their internal profile
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representation onto this fixed set.
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If there is no good match when mapping then a new profile name may be
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added. Drivers which wish to introduce new profile names must:
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1. Explain why the existing profile names cannot be used.
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2. Add the new profile name, along with a clear description of the
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expected behaviour, to the sysfs-platform_profile ABI documentation.
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