In addition to updating the contrib sources the driver now uses the
new Component API and will report the internal mixer state.
Reporting of the mixer state is enabled by adding the 'report_mixer'
attribute to the drivers configuration and setting its value to 'yes'.
The following snippets illustrates the format of the report:
!<mixer_state>
! <mixer field="inputs.beep" value="108"/>
! <mixer field="outputs.hp_sense" value="plugged"/>
! <mixer field="outputs.master" value="128,128"/>
! <mixer field="outputs.mic_sense" value="unplugged"/>
! <mixer field="outputs.spkr_muters" value="hp,mic"/>
!</mixer_state>
The mixer state may expose other mixer fields as well, depending on the
used sound card. The naming scheme of the attributes intentionally
matches the naming scheme of OpenBSD's mixerctl(1) program.
Each 'mixer' node can be used to configure the audio driver by using it
in its configuration, e.g.:
!<config report_mixer="yes">
! <mixer field="outputs.master" value="255,255"/>
!</config>
This configuration will set the output volume to the highest possible
value. Although it is now also possible to update the configuration
at run-time it should not be done while the driver is currently playing
or recording because it may provoke the generation of artefacts.
Fixes#1973.
