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diff --git a/conf.d/project/alsa.d/README.md b/conf.d/project/alsa.d/README.md new file mode 100644 index 0000000..aa2a54e --- /dev/null +++ b/conf.d/project/alsa.d/README.md @@ -0,0 +1,175 @@ + +Alsa Configuration is not complex, but it's heavy and every except intuitive. + +In order to set your configuration move step by step. And verify at each new step that you did not introduce a regression. + +### Make sure your board is not taken by PulseAudio + +* Pavucontrol is your friend. Go in device configuration and switch to off the device you want to make available to ALSA. +* Check for your device list with 'play -l'. Note that just after card number your get an alias for your sound card. + it is simpler to use this alias, card number will change depending on plug/unplug of device when this alias name + is more stable (except for few stupid driver who use 'USB' as sound card name. +* When your know your sound alias (eg:v1340 in mu case) you can test it with 'speaker-test -D v1340 -c2 -twav'. You may also + use sound card number with 'speaker-test -D hw:0 -c2 -twav'. Nevertheless as said previously this number is not stable. +* you are now ready to write your $HOME/.asoundrc config + +Note that $HOME/.asoundrc is loaded within libasound client and not by Alsa kernel, this is the reason why you do not need +to activate any control or restart a daemon for modifications to be taken in account. + +To use ALSA with AAAA and the controller you need to write 1 section in your ALSA config + +* Sound Card Mixer: Allows multiple audio stream to be played on the same sound card. If hardware support mixer, Alsa will use it. If + not it will provide mixing by software. +* Audio Role Volume: They provide independent volume for each audio role. For reference, we use Alsa softvolume, depending on + your hardware you may have this directly avaliable from your sound card. +* Authorised Audio PCM: those channel are designed for applications we do not trust and then enforce AAAA control check + before granting the access to a given channel. + +### Sound Card Mixer + +``` +pcm.SoundCardMixer { + type dmix + ipc_key 1024 + ipc_key_add_uid false + ipc_perm 0666 # mixing for all users + + # Define target effective sound card (cannot be a plugin) + slave { pcm "hw:v1340" } #Jabra Solmate + + # DMIX can only map two channels + bindings { + 0 0 + 1 1 + } +} +``` + +Warning: if you have more than one Mixer each of them should have a unique ipc_key. You sound card alias move in the slave section. +When this is done you may try your mixer with: + +``` + speaker-test -D MyMixerPCM -c2 -twav +``` + + +### Audio Role + +``` +pcm.NavigationRole { + type softvol + + # Point Slave on HOOK for policies control + slave.pcm "SoundCardMixer" + + # name should match with HAL but do not set card=xx + control.name "Playback Navigation" + +} + +``` + +The slave you point to your SoundCardMixer, and the control.name should be EXACTLY the same as the one defined in your HAL. + + +WARNING: The control here "Playback Navigation" is a user defined kernel control. It means that this kernel is created in +kernel space, but that its action happen in user space. When create those control remains visible until you reset your +sound card (eg: unplug USB), but they are save each time you reboot. It is recommended to start AAAA binder before testing +your softvol audio role channel. If you do the opposite the control will be create by Alsa Plugin and this will not inherit +of the default value you have in your HAL. + +When in place you should test it with: +``` + speaker-test -D NavigationRole -c2 -twav +``` + +IMPORTANT: control volume are attache to your physical hardware and not to intermediary level (Softvol or Mixer). To see the +newly created channel you should use +``` + amixer -Dhw:v1340 controls | grep -i playback +``` + +## Authorised Audio PCM + +This PCM is supervised with the AAAA audio hook plugin. The pluging and will any application request on this PCM and will +1st request an autorisation from AAAA controller to grant access for the client application. To do so, two things: +* the plugin should be declared (only once) +* you should declare as many authorized PCM as you need. + +### Plugin declaration + +``` +pcm_hook_type.MyHookPlugin { + install "AlsaInstallHook" + lib "/home/fulup/Workspace/AGL-AppFW/audio-bindings-dev/build/Alsa-Plugin/Alsa-Policy-Hook/policy_hook_cb.so" +} + +``` + +Lib is the path where to find AAAA Alsa hook plugin, install is the name of the init function it should not be changed. + + +When your plugin is defined you may declare your authorised PCM. Those PCM like softvol will take a slave, typically a lower +level of the audio role, or directly a mixer if your goal is to protect directly the Mixer. The AAAA Plugin hook take as + +``` +pcm.AuthorisedToNavigationOnly { + type hooks + slave.pcm "NavigationRole" + # 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&uuid=audio-agent-session" + request { + # Request autorisation to write on navigation + RequestNavigation { + api "control" + verb "dispatch" + query "{'target':'navigation', 'args':{'device':'Jabra SOLEMATE v1.34.0'}}" + } + } + # map event reception to self generated signal + event { + pause 30 + resume 31 + stop 3 + } + } + } +} + +``` + + * The slave is the PCM that application will be transfer to if access to control is granted. + * Request is a suite à control action that respond to AGL standard application framework API + * Event is the mapping of signal an appplication will receive in case AAAA controller push event to the audio application. + +When using AAAA controller, most action should be transfert to the controller that will take action to authorise/deny the access. +Nevertheless it is also possible to directly access a lower level (e.g. call alsa Use Case Manager). People may also have their +own audio policy engine and request it directly from here. + +To test this last part your need to have a controller ready to respond to your request. Otherwise control will systematically +be denied. When your AAAA controller is ready to serve your request you may check this with +``` + amixer -Dhw:AuthorisedToMusicOnly controls | grep -i playback + amixer -Dhw:AuthorisedToNavigationOnly controls | grep -i playback +``` + +IMPORTANT: you need at least to audio role to really test this part. While you may assert with one channel that your flow +to accept/deny application works. You need two simultaneous audio stream to really play with the control. Typically when playing +music if you send a navigation message then the audio will be lower during the rendering of the navigation message. + +The action on how you lower an audio role when an other one with a higger level of priority come in place not defined at the +plugin level, but in the AAAA controller, where the API control/dispatch?target=xxxxx will execute a set of actions corresponding +the set/unset accept/deny of requested control. + +Remark: to understand what is happening it is a good idea to have an alxamixer option on the your soundcard +``` + amixer -Dhw:v1340 +``` + +(!) Do not forget to replace 'hw:v1340' by what ever is the alias of your sound card.
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