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authorTakashi Iwai <tiwai@suse.de>2016-11-10 11:10:35 +0100
committerTakashi Iwai <tiwai@suse.de>2016-11-10 18:09:31 +0100
commitdf3a57105c04a7bfe0874316a9e6ec968c35a6f5 (patch)
tree0b3d0bafeef9e415ac60359672e4bd4fd20c5fd8 /Documentation/sound/alsa
parentALSA: doc: ReSTize timestamping document (diff)
downloadlinux-dev-df3a57105c04a7bfe0874316a9e6ec968c35a6f5.tar.xz
linux-dev-df3a57105c04a7bfe0874316a9e6ec968c35a6f5.zip
ALSA: doc: ReSTize Jack-Controls.txt
A simple conversion from a plain text file. Put to designs subdirectory. Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation/sound/alsa')
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diff --git a/Documentation/sound/alsa/Jack-Controls.txt b/Documentation/sound/alsa/Jack-Controls.txt
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-Why we need Jack kcontrols
-==========================
-
-ALSA uses kcontrols to export audio controls(switch, volume, Mux, ...)
-to user space. This means userspace applications like pulseaudio can
-switch off headphones and switch on speakers when no headphones are
-pluged in.
-
-The old ALSA jack code only created input devices for each registered
-jack. These jack input devices are not readable by userspace devices
-that run as non root.
-
-The new jack code creates embedded jack kcontrols for each jack that
-can be read by any process.
-
-This can be combined with UCM to allow userspace to route audio more
-intelligently based on jack insertion or removal events.
-
-Jack Kcontrol Internals
-=======================
-
-Each jack will have a kcontrol list, so that we can create a kcontrol
-and attach it to the jack, at jack creation stage. We can also add a
-kcontrol to an existing jack, at anytime when required.
-
-Those kcontrols will be freed automatically when the Jack is freed.
-
-How to use jack kcontrols
-=========================
-
-In order to keep compatibility, snd_jack_new() has been modified by
-adding two params :-
-
- - @initial_kctl: if true, create a kcontrol and add it to the jack
- list.
- - @phantom_jack: Don't create a input device for phantom jacks.
-
-HDA jacks can set phantom_jack to true in order to create a phantom
-jack and set initial_kctl to true to create an initial kcontrol with
-the correct id.
-
-ASoC jacks should set initial_kctl as false. The pin name will be
-assigned as the jack kcontrol name.