From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jie Yang Subject: [PATCH v10 7/7] ALSA: Docs: Add documentation for Jack kcontrols Date: Mon, 27 Apr 2015 21:21:02 +0800 Message-ID: <1430140862-17207-8-git-send-email-yang.jie@intel.com> References: <1430140862-17207-1-git-send-email-yang.jie@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by alsa0.perex.cz (Postfix) with ESMTP id A6C98265275 for ; Mon, 27 Apr 2015 15:17:46 +0200 (CEST) In-Reply-To: <1430140862-17207-1-git-send-email-yang.jie@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: tiwai@suse.de Cc: alsa-devel@alsa-project.org, broonie@kernel.org, tanu.kaskinen@linux.intel.com, liam.r.girdwood@intel.com List-Id: alsa-devel@alsa-project.org Add documentation describing Jack kcontrols and how to use them with HD-Audio and ASoC. Signed-off-by: Jie Yang --- Documentation/sound/alsa/Jack-Controls.txt | 43 ++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 Documentation/sound/alsa/Jack-Controls.txt diff --git a/Documentation/sound/alsa/Jack-Controls.txt b/Documentation/sound/alsa/Jack-Controls.txt new file mode 100644 index 0000000..fe1c5e0 --- /dev/null +++ b/Documentation/sound/alsa/Jack-Controls.txt @@ -0,0 +1,43 @@ +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. -- 1.9.1