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SubjectRe: [PATCH v2 1/3] ALSA: compress: document the compress audio state machine
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On 6/22/20 1:58 AM, Vinod Koul wrote:
> So we had some discussions of the stream states, so I thought it is a
> good idea to document the state transitions, so add it documentation
>
> Signed-off-by: Vinod Koul <vkoul@kernel.org>
> ---
> .../sound/designs/compress-offload.rst | 52 +++++++++++++++++++
> 1 file changed, 52 insertions(+)
>
> diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst
> index ad4bfbdacc83..6f86db82298b 100644
> --- a/Documentation/sound/designs/compress-offload.rst
> +++ b/Documentation/sound/designs/compress-offload.rst
> @@ -151,6 +151,58 @@ Modifications include:
> - Addition of encoding options when required (derived from OpenMAX IL)
> - Addition of rateControlSupported (missing in OpenMAX AL)
>
> +State Machine
> +=============
> +
> +The compressed audio stream state machine is described below ::
> +
> + +----------+
> + | |
> + | OPEN |
> + | |
> + +----------+
> + |
> + |
> + | compr_set_params()
> + |
> + v
> + compr_free() +----------+
> + +-------------------------------------| |
> + | | SETUP |
> + | +------------------------>| |<---------------------------------+
> + | | compr_drain_notify() +----------+ |
> + | | | |
> + | | | |
> + | | | compr_write() |
> + | | | |
> + | | v |
> + | | +----------+ |
> + | | | | |
> + | | | PREPARE | |
> + | | | | |
> + | | +----------+ |
> + | | | |
> + | | | |
> + | | | compr_start() |
> + | | | |
> + | | v |
> + | +----------+ +----------+ compr_pause() +----------+ |
> + | | | compr_drain() | |---------------->| | |
> + | | DRAIN |<-------------------| RUNNING | | PAUSE | |
> + | | | | |<----------------| | |
> + | +----------+ +----------+ compr_resume() +----------+ |
> + | | | | |
> + | | | | |
> + | | | | |
> + | | | | compr_stop() |
> + | | | +------------------------------------+
> + | | +----------+ |
> + | | | | |
> + +-----------+------>| |<-------+
> + compr_free() | FREE | compr_free()
> + | |
> + +----------+
> +

Sorry, this confuses me even more...

a) can you clarify if we can go from running to free directly? is this
really a legit transition? There's already the option of doing a stop
and a a drain.

b) no way to go back to SETUP from PREPARE? What happens if the app
never starts but want to tear down the resources?

c) no way to stop a paused stream?

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