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From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
To: Clemens Ladisch <clemens@ladisch.de>
Cc: tiwai@suse.de, alsa-devel@alsa-project.org,
	linux1394-devel@lists.sourceforge.net, ffado-devel@lists.sf.net
Subject: Re: [PATCH 26/44] fireworks: Add PCM interface
Date: Mon, 07 Apr 2014 16:20:14 +0900	[thread overview]
Message-ID: <534251AE.4020308@sakamocchi.jp> (raw)
In-Reply-To: <53416A44.6070905@ladisch.de>

Hi Clemens,

(Apr 6 2014 23:52), Clemens Ladisch wrote:
>>>> +static int pcm_open(struct snd_pcm_substream *substream)
>>>> +{
>>>> +    ...
>>>> +    /*
>>>> +     * When source of clock is not internal or any PCM streams are running,
>>>> +     * available sampling rate is limited at current sampling rate.
>>>> +     */
>>>> +    if ((clock_source != SND_EFW_CLOCK_SOURCE_INTERNAL) ||
>>>> +        amdtp_stream_pcm_running(&efw->tx_stream) ||
>>>> +        amdtp_stream_pcm_running(&efw->rx_stream)) {
>>>
> There is already a mutex for everything in start_duplex(), so the only
> unprotected piece of data is this counter.

Yes. I think atomic_t mostly solves the issue.


But these codes (in PCM .open) includes another issue which brings a 
great headache to me.

The driver uses SNDRV_PCM_INFO_JOINT_DUPLEX. So sampling rate for 
playback/capture should be the same. But there is a case to allow 
applications to break this rule.

Let's assume that two applications try to use PCM functionality. 
Application 1 is for 48.0kHz playback, and Application 2 is for 88.2kHz 
capture. In this case, Application 1 write 48.0kHz samples on 88.2kHz 
streams:

Application 1: snd_pcm_open() for playback
Application 1: snd_pcm_hw_params() at 48.0kHz
(snd_pcm_prepare() and AMDTP streams start)
Application 2: snd_pcm_open() for capture
Application 2: snd_pcm_hw_params() at 88.2kHz
(snd_pcm_prepare() and AMDTP streams re-start)
Application 2: read PCM samples
Application 1: write PCM samples

The reason to allow snd_pcm_prepare() to restart streams at different 
sampling rate is to continue MIDI substreams at different sampling rate.

I've been considering about this issue for several months but still have 
no good ideas...

But I think this is actually too rare. I assume most applications 
write/read samples after snd_pcm_hw_params() as soon as possible and 
most sound server uses the same sampling rate for its capturing/playbacking.

So I hope this issue pending for my future work.


Thanks

Takashi Sakamoto
o-takashi@sakamocchi.jp


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  reply	other threads:[~2014-04-07  7:20 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-21 11:09 [PATCH 00/44 v3] Enhancement of support for Firewire devices Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 01/44] firewire-lib: Add macros instead of fixed value for AMDTP Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 02/44] firewire-lib: Add 'direction' member to 'amdtp_stream' structure Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 03/44] firewire-lib: Split some codes into functions to reuse for both streams Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 04/44] firewire-lib: Add support for AMDTP in-stream and PCM capture Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 05/44] firewire-lib: Add support for MIDI capture/playback Takashi Sakamoto
2014-04-02 19:29   ` Clemens Ladisch
2014-04-02 19:42     ` [FFADO-devel] " Adrian Knoth
2014-04-02 19:58       ` Clemens Ladisch
2014-04-02 20:37         ` [FFADO-devel] [alsa-devel] " Jano Svitok
2014-04-03  8:33     ` Takashi Sakamoto
2014-04-03  8:54       ` Clemens Ladisch
2014-04-03 10:08         ` Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 06/44] firewire-lib: Give syt value as parameter to handle_out_packet() Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 07/44] firewire-lib: Add support for duplex streams synchronization in blocking mode Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 08/44] firewire-lib: Add support for channel mapping Takashi Sakamoto
2014-04-02 20:18   ` Clemens Ladisch
2014-04-03  8:37     ` Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 09/44] firewire-lib: Restrict calling flush_context_completion() when context exists Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 10/44] firewire-lib: Rename macros, variables and functions for CMP Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 11/44] firewire-lib: Add 'direction' member to 'cmp_connection' structure Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 12/44] firewire-lib: Add handling output connection by CMP Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 13/44] firewire-lib: Add a new function to check others' connection Takashi Sakamoto
2014-03-21 11:09 ` [PATCH 14/44] firewire-lib: Add support for deferred transaction Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 15/44] firewire-lib: Add some AV/C general commands Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 16/44] fireworks: Add skelton for Fireworks based devices Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 17/44] fireworks: Add transaction and some commands Takashi Sakamoto
2014-04-03 20:15   ` Clemens Ladisch
2014-04-04  4:08     ` Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 18/44] fireworks: Add connection and stream management Takashi Sakamoto
2014-04-03 20:56   ` Clemens Ladisch
2014-04-04 14:22     ` Takashi Sakamoto
2014-04-04 15:05       ` [alsa-devel] " Clemens Ladisch
2014-04-06 13:20         ` Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 19/44] fireworks/firewire-lib: Add a quirk for empty packet with TAG0 Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 20/44] fireworks/firewire-lib: Add a quirk for the meaning of dbc Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 21/44] fireworks/firewire-lib: Add a quirk for wrong dbs in tx packets Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 22/44] fireworks/firewire-libs: Add a quirk for fixed interval of reported dbc Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 23/44] fireworks: Add proc interface for debugging purpose Takashi Sakamoto
2014-04-03 21:16   ` [alsa-devel] " Clemens Ladisch
2014-04-04 11:16     ` Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 24/44] fireworks: Add MIDI interface Takashi Sakamoto
2014-04-03 21:20   ` [alsa-devel] " Clemens Ladisch
2014-04-06 12:03     ` Takashi Sakamoto
2014-04-06 14:52       ` Clemens Ladisch
2014-04-07 12:59         ` Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 25/44] fireworks/firewire-lib: Add a quirk for data blocks for MIDI in out-stream Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 26/44] fireworks: Add PCM interface Takashi Sakamoto
2014-04-04  8:48   ` Clemens Ladisch
2014-04-06 12:44     ` Takashi Sakamoto
2014-04-06 14:52       ` [alsa-devel] " Clemens Ladisch
2014-04-07  7:20         ` Takashi Sakamoto [this message]
2014-03-21 11:10 ` [PATCH 27/44] fireworks: Add hwdep interface Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 28/44] fireworks: Add command/response functionality into " Takashi Sakamoto
2014-04-04  9:31   ` Clemens Ladisch
2014-04-04 11:11     ` Takashi Sakamoto
2014-04-04 12:15       ` [alsa-devel] " Clemens Ladisch
2014-04-08  2:45         ` Takashi Sakamoto
2014-04-04 15:13   ` Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 29/44] bebob: Add skelton for BeBoB based devices Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 30/44] bebob: Add commands and connections/streams management Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 31/44] bebob/firewire-lib: Add a quirk for discontinuity at bus reset Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 32/44] bebob: Add proc interface for debugging purpose Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 33/44] bebob: Add MIDI interface Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 34/44] bebob: Add PCM interface Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 35/44] bebob: Add hwdep interface Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 36/44] bebob: Prepare for device specific operations Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 37/44] bebob: Add support for Terratec PHASE, EWS series and Aureon Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 38/44] bebob: Add support for Yamaha GO series Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 39/44] bebob: Add support for Focusrite Saffire/SaffirePro series Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 40/44] bebob: Add support for M-Audio usual Firewire series Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 41/44] bebob: Add support for M-Audio special " Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 42/44] bebob/firewire-lib: Add a quirk of wrong dbc in empty packet " Takashi Sakamoto
2014-03-23  2:16   ` Takashi Sakamoto
2014-03-24  1:41     ` [FFADO-devel] " Euan de Kock
2014-03-24  2:52       ` Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 43/44] bebob: Send a cue to load firmware for M-Audio " Takashi Sakamoto
2014-03-21 11:10 ` [PATCH 44/44] firewire/bebob: Add a workaround for M-Audio special " Takashi Sakamoto
2014-04-02 11:15 ` [PATCH 00/44 v3] Enhancement of support for Firewire devices Takashi Sakamoto
2014-04-03 19:17 ` David Henningsson
2014-04-04  7:04   ` Takashi Iwai

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