28 lines
935 B
ReStructuredText
28 lines
935 B
ReStructuredText
============
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Introduction
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============
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The firmware API enables kernel code to request files required
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for functionality from userspace, the uses vary:
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* Microcode for CPU errata
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* Device driver firmware, required to be loaded onto device
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microcontrollers
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* Device driver information data (calibration data, EEPROM overrides),
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some of which can be completely optional.
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Types of firmware requests
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==========================
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There are two types of calls:
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* Synchronous
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* Asynchronous
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Which one you use vary depending on your requirements, the rule of thumb
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however is you should strive to use the asynchronous APIs unless you also
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are already using asynchronous initialization mechanisms which will not
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stall or delay boot. Even if loading firmware does not take a lot of time
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processing firmware might, and this can still delay boot or initialization,
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as such mechanisms such as asynchronous probe can help supplement drivers.
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