Alsa-Hook-Plugin Object: Provide a Hook on Alsa PCM to check permission again AGL Advance Audio Agent Status: Release Candidate Author: Fulup Ar Foll fulup@iot.bzh Date : August-2017 Functionalities: - Execute a set of websocket RPC request again AGL binders to allow/deny access - Keep websocket open in an idepandant thread on order to monitor event receive from AGL audio agent Installation - Alsaplugins are typically search in /usr/share/alsa-lib. Nevertheless a full path might be given - This plugin implement a hook on a slave PCM. Typically this slave PCM is a dedicated virtual channel (eg: navigation, emergency,...) - Config should be place in ~/.asoundrc (see config sample in PROJECT_ROOT/conf.d/alsa) Test - Install a full .asoundrc from conf.d/project/alsa.d - speaker-test -DMyNavigationHook -c2 -twav Config ``` # Define sharelib location and entry point # ----------------------------------------- pcm_hook_type.MyHookPlugin { install "AlsaInstallHook" lib "/home/fulup/Workspace/AGL-AppFW/audio-bindings-dev/build/Alsa-Plugin/Alsa-Hook-Callback/alsa_hook_cb.so" } # Create PCM HOOK with corresponding request calls to AGL Audio Agent # -------------------------------------------------------------------- pcm.MyNavigationHook { type hooks slave.pcm "MyMixerPCM" # Defined used hook sharelib and provide arguments/config to install func hooks.0 { type "MyHookPlugin" hook_args { verbose true # print few log messages (default false); # Every Call should return OK in order PCM to open (default timeout 100ms) uri "ws://localhost:1234/api?token='audio-agent-token'" request { # Request authorisation to write on navigation navigation-ctl { api "pol4a" request "navigation-role" release "navigation-role" args "{'uid':'alsa-hook-navigation'}" } # subscribe to Audio Agent Event map them to signal subscribe-evt { api "pol4a" verb "subscribe" } } # map event reception to self generated signal event { pause 30 resume 31 stop 3 } } } } ``` NOTE: * Hook plugin is loaded by Alsa libasound within player context. It inherits client process attributes, as UID/GID or the SMACK label on AGL. This smack label is tested by AGL security framework when requested a call on the audio-agent binder. As a result the call will only succeed it the permission attached the application in Cynara matches. * Hook plugin keep a connection with the Audio-Agent until PCM is closed by the application. This connection allow the Audio-Agent to send events. eg: pause, quit, mute, ...