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Diffstat (limited to 'Documentation/sound/alsa')
| -rw-r--r-- | Documentation/sound/alsa/Jack-Controls.txt | 43 |
1 files changed, 0 insertions, 43 deletions
diff --git a/Documentation/sound/alsa/Jack-Controls.txt b/Documentation/sound/alsa/Jack-Controls.txt deleted file mode 100644 index fe1c5e0c8555..000000000000 --- a/Documentation/sound/alsa/Jack-Controls.txt +++ /dev/null @@ -1,43 +0,0 @@ -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. |