1 ============ 1 ============
2 Introduction 2 Introduction
3 ============ 3 ============
4 4
5 The firmware API enables kernel code to reques 5 The firmware API enables kernel code to request files required
6 for functionality from userspace, the uses var 6 for functionality from userspace, the uses vary:
7 7
8 * Microcode for CPU errata 8 * Microcode for CPU errata
9 * Device driver firmware, required to be loade 9 * Device driver firmware, required to be loaded onto device
10 microcontrollers 10 microcontrollers
11 * Device driver information data (calibration 11 * Device driver information data (calibration data, EEPROM overrides),
12 some of which can be completely optional. 12 some of which can be completely optional.
13 13
14 Types of firmware requests 14 Types of firmware requests
15 ========================== 15 ==========================
16 16
17 There are two types of calls: 17 There are two types of calls:
18 18
19 * Synchronous 19 * Synchronous
20 * Asynchronous 20 * Asynchronous
21 21
22 Which one you use vary depending on your requi 22 Which one you use vary depending on your requirements, the rule of thumb
23 however is you should strive to use the asynch 23 however is you should strive to use the asynchronous APIs unless you also
24 are already using asynchronous initialization 24 are already using asynchronous initialization mechanisms which will not
25 stall or delay boot. Even if loading firmware 25 stall or delay boot. Even if loading firmware does not take a lot of time
26 processing firmware might, and this can still 26 processing firmware might, and this can still delay boot or initialization,
27 as such mechanisms such as asynchronous probe 27 as such mechanisms such as asynchronous probe can help supplement drivers.
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