From 070ccac33d65c651c972dfab9c6148e43d8d5d8e Mon Sep 17 00:00:00 2001 From: fulup Date: Thu, 3 Aug 2017 12:00:41 +0200 Subject: Initial Working Version on Alsa Policy-Policy-Hook --- Alsa-Plugin/_Alsa-Hal-plugin/README.md | 44 ++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 Alsa-Plugin/_Alsa-Hal-plugin/README.md (limited to 'Alsa-Plugin/_Alsa-Hal-plugin/README.md') diff --git a/Alsa-Plugin/_Alsa-Hal-plugin/README.md b/Alsa-Plugin/_Alsa-Hal-plugin/README.md new file mode 100644 index 0000000..1c1e7a2 --- /dev/null +++ b/Alsa-Plugin/_Alsa-Hal-plugin/README.md @@ -0,0 +1,44 @@ +Hal-Plugin + +Object: provide an ALSA a HAL (Hardware Abstraction Layer) to automotive sound cards +Status: Current version is proof of concept and not a usable product +Author: Fulup Ar Foll +Date : June-2017 + +HAL-plugin allows: + - to expose any existing NUMID under a customized label name, this is order to abstract sound card config. + - to add non alsa NUMID supported through a callback mechanism (eg: volume rampdown, power off, ...) + +installation + - Plugin should be placed where ever alsaplugins are located (typically: /usr/share/alsa-lib) + - Callback sharelib directory should be declare in $LD_LIBRARY_PATH + +Config +``` +cat ~/.asoundrc + ctl.agl_hal { + type afbhal + devid "hw:4" + cblib "afbhal_cb_sample.so" + ctls { + # ctlLabel {numid integer name "Alsa Ctl Name"} + MasterSwitch { numid 4 name "My_First_Control" } + MasterVol { numid 5 name "My_Second_Control" } + CB_sample { ctlcb @AfbHalSampleCB name "My_Sample_Callback"} + } + pcm.agl_hal { + type copy # Copy PCM + slave "hw:4" # Slave name + } +``` + +With such a config file + - numid=4 from sndcard=hw:4 is renamed "My_First_Control" + - numid=4 from sndcard=hw:4 is renamed "My_Second_Control" + - numid=4 will call AfbHalSampleCB from afbhal_cb_sample.so + +Note: to really implement a usable HAL at minimum every ALSA call should be implemented and read/write of values should be normalised from 0 to 100% with a step of 1. + +Conclusion: This demonstrate that implementing a HAL that both abstract ALSA get/set and enable non ALSA support is possible at an acceptable cost +without having to hack ALSA source code. The beauty of the model is than it is fully transparent to any ALSA application. The limit is that the plugin is loaded +within every application context, thus interaction with an external event loop remains complete as well as conflict management in case of share resources. -- cgit 1.2.3-korg