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Subject: [PATCH] virtio-snd: improve PCM command lifecycle description
The PCM command lifecycle can be described as a state-machine in which the switching between states is triggered by commands. This commit explicitly presents the different states and the commands that are allowed in a given state. This commit leaves to the implementation the decision the state reached depending on the command. Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> --- device-types/sound/description.tex | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff --git a/device-types/sound/description.tex b/device-types/sound/description.tex index 54c9c8e..55e93af 100644 --- a/device-types/sound/description.tex +++ b/device-types/sound/description.tex @@ -397,9 +397,21 @@ \subsubsection{PCM Control Messages}\label{sec:Device Types / Sound Device / Dev \item[\field{stream_id}] specifies a PCM stream identifier from 0 to \field{streams} - 1. \end{description} -\paragraph{PCM Command Lifecycle} +\paragraph{PCM Command Lifecycle State Machine} -A PCM stream has the following command lifecycle: +A PCM stream can be represented by a state-machine made up of the following +states: +\begin{description} +\item SET PARAMETERS +\item PREPARE +\item START +\item STOP +\item RELEASE +\end{description} + +A command triggers the transition between these states. To what state to switch +depends on the implementation. Depending on the state, only certain commands +are valid. An error may occur if an invalid command is triggered. \begin{enumerate} \item SET PARAMETERS @@ -407,13 +419,13 @@ \subsubsection{PCM Control Messages}\label{sec:Device Types / Sound Device / Dev The driver negotiates the stream parameters (format, transport, etc) with the device. -Possible valid transitions: set parameters, prepare. +Possible valid commands: set parameters, prepare. \item PREPARE The device prepares the stream (allocates resources, etc). -Possible valid transitions: set parameters, prepare, start, release. +Possible valid commands: set parameters, prepare, start, release. \item Output only: the driver transfers data for pre-buffing. @@ -421,7 +433,7 @@ \subsubsection{PCM Control Messages}\label{sec:Device Types / Sound Device / Dev The device starts the stream (unmute, putting into running state, etc). -Possible valid transitions: stop. +Possible valid commands: stop. \item The driver transfers data to/from the stream. @@ -429,13 +441,13 @@ \subsubsection{PCM Control Messages}\label{sec:Device Types / Sound Device / Dev The device stops the stream (mute, putting into non-running state, etc). -Possible valid transitions: start, release. +Possible valid commands: start, release. \item RELEASE The device releases the stream (frees resources, etc). -Possible valid transitions: set parameters, prepare. +Possible valid commands: set parameters, prepare. \end{enumerate} -- 2.41.0
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