The VFS OSS plugin offers access to Genode's Audio_out session by providing a
file-system that can be mounted at arbitrary location within the VFS of a
component. It exposes a data file that can by used as 'dsp' file, e.g., _/dev/dsp_
as is common with OSS. The support I/O control operations or rather the
properties of the pseudo-device are provide in form of a structured 'info'
file located in the directory named after the data file, e.g., _/dev/.dsp/info_.

This file may by used to query the configured parameters and has the following
structure:

! <oss channels="2" sample_rate="44000" format="16"
!      queue_size="256" frag_size="1024" frag_avail="256"/>

Each parameter can also be accessed via its own file. The following list
presents all files:

  * :channels: number of available channels. Set to 2 (stereo).

  * :sample_rate: sample rate of the underlying Audio_out session.

  * :format: sample format, e.g. s16le. Defaults to AFMT_S16_LE.

  * :queue_size: number of packets in the underlying Audio_out session's
    packet-stream.

  * :frag_size: size of a fragment. Set to 1024 (number of channels times
    size of Audio_out period times size of s16le sample).

  * :frag_avail: number of available bytes. Initially set to queue size
    times frag size.

In its current state it is merely enough to use simply applications requiring
nothing more than a minimal set of the OSSv3 API. It does not allow altering
of parameters. Therefore it will only work when 44000Hz/s16le is used.

The following config snippets illustrates its configuration:

! <vfs>
!   <dir name="dev">
!     <oss name="dsp"/>
!   </dir>
! </vfs>
