[alsa-devel] [PATCH - JACK plugin 4/4] jack: Support snd_pcm_drain()

[Wischer, Timo (ADITG/ESB)]

Hello Jaroslav

> Do you handle the non-blocking mode correctly here? It seems that this
> mode is completely ignored.

You are right. The non-blocking mode flag will be ignored here.
But this case is also not covered by the IO plug API.
snd_pcm_drop() is called immediately after the IO plugin drain callback returns [1].
The return value of the drain callback will be ignored.

Therefore the IO plug API has to be changed to support this.
But I do not really see a use case for it.
If you want to drain you also want to wait/block your application until all frames were played.

If you think it is required to change anything in this patch
we have to clarify when drop should be called and when not.
What is the sequence which the user would expect?
Does the user need to call drop after drain is done or would it be called by snd_pcm_wait/snd_pcm_drain when it is not returning -EAGAIN?

[1] http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/pcm/pcm_ioplug.c;h=8c0ed4836365afb53c0cbce796a5d39c2d05a3d7;hb=07a17bd5a50289e2fdb2714a4e39f38f41811558#l504

Best regards

Timo Wischer

Advanced Driver Information Technology GmbH
Engineering Software Base (ADITG/ESB)
Robert-Bosch-Str. 200
31139 Hildesheim
Germany

Tel. +49 5121 49 6938
Fax +49 5121 49 6999
twischer at de.adit-jv.com

ADIT is a joint venture company of Robert Bosch GmbH/Robert Bosch Car Multimedia GmbH and DENSO Corporation
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________________________________________
From: Jaroslav Kysela [perex at perex.cz]
Sent: Thursday, March 01, 2018 2:42 PM
To: Wischer, Timo (ADITG/ESB)
Cc: ALSA development; Takashi Iwai
Subject: Re: [alsa-devel] [PATCH - JACK plugin 4/4] jack: Support snd_pcm_drain()

Dne 1.3.2018 v 14:14 twischer at de.adit-jv.com napsal(a):
> From: Timo Wischer <twischer at de.adit-jv.com>
>
> Block on drain till available samples played

Do you handle the non-blocking mode correctly here? It seems that this
mode is completely ignored.

                                        Jaroslav

--
Jaroslav Kysela <perex at perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.