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SubjectRe: [PATCH v4 1/3] ALSA: compress: document the compress audio state machine
Hi Amadeusz,

On 29-06-20, 11:05, Amadeusz Sławiński wrote:
>
>
> On 6/29/2020 9:50 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
> >
> > Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
> > Signed-off-by: Vinod Koul <vkoul@kernel.org>
> > ---
> > .../sound/designs/compress-offload.rst | 51 +++++++++++++++++++
> > 1 file changed, 51 insertions(+)
> >
> > diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst
> > index ad4bfbdacc83..b6e9025ae105 100644
> > --- a/Documentation/sound/designs/compress-offload.rst
> > +++ b/Documentation/sound/designs/compress-offload.rst
> > @@ -151,6 +151,57 @@ 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() +----------+ |
> > + | | or ^ |
> > + | | compr_stop() | |
> > + | | | compr_write() |
> > + | | | |
> > + | | | |

Not sure, this is not in the version I posted, arrow is from setup ->
prepare. See https://lore.kernel.org/alsa-devel/20200629075002.11436-2-vkoul@kernel.org/

I don't know how it got reversed in your version, maybe the MUA messed
up??

> > + | | +----------+ |
> > + | | | | compr_free() |
> > + | | | PREPARE |---------------> A |
> > + | | | | |
> > + | | +----------+ |
> > + | | | |
> > + | | | |
> > + | | | compr_start() |
> > + | | | |
> > + | | v |
> > + | +----------+ +----------+ |
> > + | | | compr_drain() | | compr_stop() |
> > + | | DRAIN |<-------------------| RUNNING |--------------------------+
> > + | | | | | |
> > + | +----------+ +----------+ |
> > + | | ^ |
> > + | A | | |
> > + | | compr_pause() | | compr_resume() |
> > + | | | | |
> > + | v v | |
> > + | +----------+ +----------+ |
> > + | | | | | compr_stop() |
> > + +--->| FREE | | PAUSE |---------------------------+
> > + | | | |
> > + +----------+ +----------+
> > +
> > Gapless Playback
> > ================
> >
>
> Line containing compr_free (between SETUP and FREE) seems to be misaligned?

not in the version I posted and see on lore

> If you move prepare to the left and drain in place of drain, it feels like
> you won't need this weird indirection with A

yeah that was a compromise to make it bit neater to me than adding
overlapping arrows...

> Something like:
>
> >> + v
> > > + compr_free() +----------+
> > > + +------------------------------------| |
> > > + | | SETUP |
> > > + | +------------------------>| |<-------------------------+
> > > + | | compr_write() +----------+ |
> > > + | | ^ |
> > > + | | | compr_drain_notify() or |
> > > + | | | compr_stop() |
> > > + | | | |
> > > + | | | |
> > > + | | +----------+ |
> > > + | | | | |
> > > + | | | DRAIN | |
> > > + | | | | |
> > > + | | +----------+ |
> > > + | | ^ |
> > > + | | | |
> > > + | | | compr_drain() |
> > > + | | | |
> > > + | | | |
> > > + | +----------+ +----------+ |
> > > + | | | compr_start() | | compr_stop() |
> > > + | | PREPARE |------------------->| RUNNING |--------------------------+
> > > + | | | | | |
> > > + | +----------+ +----------+ |
> > > + | | | ^ |
> > > + | | compr_free() | | |
> > > + | | compr_pause() | | compr_resume() |
> > > + | | | | |
> > > + | v v | |
> > > + | +----------+ +----------+ |
> > > + | | | | | compr_stop() |
> > > + +--->| FREE | | PAUSE |---------------------------+
> > > + | | | |
> > > + +----------+ +----------+
> > > +
>

> but this makes me question PREPARE state, how do you enter it?

a compr_write() moves from SETUP -> PREPARE. Fixing that above looks
better version of mine..

--
~Vinod

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