1 ===================
2 ASoC jack detection
3 ===================
4
5 ALSA has a standard API for representing physi
6 the kernel side of which can be seen in includ
7 provides a version of this API adding two addi
8
9 - It allows more than one jack detection meth
10 user visible jack. In embedded systems it
11 to be present on a single jack but handled
12 hardware.
13
14 - Integration with DAPM, allowing DAPM endpoi
15 automatically based on the detected jack st
16 headphone outputs if no headphones are pres
17
18 This is done by splitting the jacks up into th
19 together: the jack itself represented by a str
20 snd_soc_jack_pins representing DAPM endpoints
21 code providing jack reporting mechanisms.
22
23 For example, a system may have a stereo headse
24 mechanisms, one for the headphone and one for
25 systems won't be able to use their speaker out
26 connected and so will want to make sure to upd
27 headphone when the headphone jack status chang
28
29 The jack - struct snd_soc_jack
30 ==============================
31
32 This represents a physical jack on the system
33 user space. The jack itself is completely pas
34 machine driver and updated by jack detection m
35
36 Jacks are created by the machine driver callin
37
38 snd_soc_jack_pin
39 ================
40
41 These represent a DAPM pin to update depending
42 bits supported by the jack. Each snd_soc_jack
43 which are updated automatically. They are cre
44 and associated with the jack using snd_soc_jac
45 of the endpoint may configured to be the oppos
46 required (eg, enabling a built in microphone i
47 connected via a jack).
48
49 Jack detection methods
50 ======================
51
52 Actual jack detection is done by code which is
53 input to the system and update a jack by calli
54 specifying a subset of bits to update. The ja
55 be set up by the machine driver, taking config
56 update and the set of things to report when th
57
58 Often this is done based on the status of a GP
59 provided by the snd_soc_jack_add_gpio() functi
60 also available, for example integrated into CO
61 CODEC integrated jack detection can be see in
62
63 Each jack may have multiple reporting mechanis
64 least one to be useful.
65
66 Machine drivers
67 ===============
68
69 These are all hooked together by the machine d
70 system hardware. The machine driver will set
71 the list of pins to update then set up one or
72 mechanisms to update that jack based on their
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