Re: [virtio-comment] [PATCH] virtio-snd: add support for audio controls

On Tue, Apr 20 2021, Anton Yakovlev <> wrote:

> This patch extends the virtio sound device specification by adding
> support for audio controls. Audio controls can be used to set the volume
> level, mute/unmute the audio signal, switch different modes/states of
> the virtual sound device, etc.
>
> Signed-off-by: Anton Yakovlev <>
> ---
>  conformance.tex  |   5 +
>  virtio-sound.tex | 374 ++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 378 insertions(+), 1 deletion(-)
>

> @@ -50,6 +53,7 @@ \subsection{Device Configuration Layout}\label{sec:Device Types / Sound Device /
>      le32 jacks;
>      le32 streams;
>      le32 chmaps;
> +    le32 controls;
>  };
>  \end{lstlisting}
>  
> @@ -62,6 +66,9 @@ \subsection{Device Configuration Layout}\label{sec:Device Types / Sound Device /
>  PCM streams.
>  \item[\field{chmaps}] (driver-read-only) indicates a total number of all available
>  channel maps.
> +\item[\field{controls}] (driver-read-only) indicates a total number of all available
> +control elements if VIRTIO_SND_F_CTLS has been negotiated.

While the driver is not supposed to read this if the feature has not
been negotiated, do we also want to add a normative statement about what
the device is supposed to do in this case? Does the field always exist?

> +
>  \end{description}
>  
>  \subsection{Device Initialization}

Does anyone familiar with virtio-snd want to take a look at this update?