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 unix/ws RPC request again AGL binders to allow/deny access - Keep websocket open in an idependant thread in order to monitor event received 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 ``` # # Author: Fulup Ar Foll # Object: PCM hook type # # Test : Note: Jabra_USB=hw:v1340 # Check SoundCard ==> speaker-test -Dhw:v1340 -c2 -twav # Check MixerPCM ==> speaker-test -DSpeakers -c2 -twav # Check SoftVol ==> speaker-test -DMusicPCM -c2 -twav # Check Plugin ==> speaker-test -DMultimedia -c2 -twav # MultiMedia aplay -DDMyNavPCM /usr/share/sounds/alsa/test.wav # # Bug/Feature: when softvol control is initialised from plugin and not # from AGL binding. At 1st run ctl has invalid TLV and cannot be # use. Bypass Solution: # * start audio-binder before playing sound (binding create control before softvol plugin) # * run a dummy aplay -DMyNavPCM "" to get a clean control # # References: https://www.spinics.net/lists/alsa-devel/msg54235.html # -------------------------------------------------------------------- # ------------------------------------------------------ # Mixer PCM allow to play multiple stream simultaneously # ------------------------------------------------------ pcm.Speakers { type dmix slave {pcm "hw:v1340"} #Jabra Solmate 1 ipc_key 1001 # ipc_key should be unique to each dmix } # ----------------------------------------------------- # Register ControllerHookPlugin (ToiBeFix fullpath) # ----------------------------------------------------- pcm_hook_type.CtlHookPlugin { install "AlsaInstallHook" lib "/home/fulup/Workspace/Audio-4a/alsa-4a/build/hook-plugin/policy_hook_cb.so" } # ------------------------------------------------------- # Define one Audio Virtual Channel per Audio Roles # ------------------------------------------------------- pcm.MusicPCM { type softvol # Point Slave on HOOK for policies control slave.pcm "Speakers" # name should match with HAL definition control.name "Playback Multimedia" } pcm.NavPCM { type softvol # Point Slave on HOOK for policies control slave.pcm "Speakers" # name should match with HAL definition control.name "Playback Navigation" } pcm.UrgentPCM { type softvol # Point Slave on HOOK for policies control slave.pcm "Speakers" # name should match with HAL definition control.name "Playback Emergency" } # ---------------------------------------------------- # Define one hooked PCM channel per Audio Roles # ---------------------------------------------------- pcm.Multimedia { type hooks slave {pcm "MusicPCM"} hooks.0 { comment "Defined used hook sharelib and provide arguments/config to install func" type "CtlHookPlugin" hook_args { # print few log messages (default false) verbose true # uri to audio-4a policy engine ws-client="unix:/var/tmp/pol4a" # api subcall to request a role controls { # Request authorisation to write on navigation navigation-ctl { request "navigation-role" release "release-role" args "{'uid':'alsa-hook-navigation'}" } } events { # map event reception to self generated signal pause 30 resume 31 stop 3 } } } } ``` NOTE: * Hook plugin is loaded by Alsa libasound within client context. It inherits client process attributes, as UID/GID and SMACK label when running on AGL. The smack label is control by AGL security framework. As a result a control request succeeds only when client application permission match requested audio role inside Cynara security database. * 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, ...