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Message-ID: <20200623040517.GO2324254@vkoul-mobl>
Date: Tue, 23 Jun 2020 09:35:17 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc: Takashi Iwai <tiwai@...e.com>, Jaroslav Kysela <perex@...ex.cz>,
alsa-devel@...a-project.org,
Charles Keepax <ckeepax@...nsource.cirrus.com>,
linux-arm-msm@...r.kernel.org,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] ALSA: compress: document the compress audio state
machine
On 22-06-20, 08:28, Pierre-Louis Bossart wrote:
>
>
> 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@...nel.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...
Oops
> 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.
As Charles pointed it is legit one, but then from SM we should remove
running->free arrow to clarify. Internally, free in running, draining
and paused triggers a stop and then free.
> b) no way to go back to SETUP from PREPARE? What happens if the app never
> starts but want to tear down the resources?
See above, free would trigger an internal step to stop (setup) and then
freed.
Btw I am not adding changes to code but documenting the 'existing'
behaviour, so a code lookup will help
> c) no way to stop a paused stream?
Yes missed that, will add.
--
~Vinod
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