From: Mark Brown <broonie@opensource.wolfsonmicro.com>
To: "Harrod, John" <john.harrod@philips.com>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>
Subject: Re: Triggering a DAPM widget event
Date: Wed, 26 Jan 2011 18:27:54 +0000 [thread overview]
Message-ID: <20110126182754.GJ8501@opensource.wolfsonmicro.com> (raw)
In-Reply-To: <39D4D143FC30524CAB784A72ADFECEEE34A0E8F3DF@NLCLUEXM02.connect1.local>
On Wed, Jan 26, 2011 at 07:08:31PM +0100, Harrod, John wrote:
http://daringfireball.net/2007/07/on_top
> I ran a few experiments where I frequently opened and closed the PCM. Under
> a heavy load, I sometimes get a resource busy error when I use the
> snd_pcm_open() call. So it looks like alsa-lib is not designed for frequent
Two issues here:
- Opening and closing streams are not the same thing as stopping and
starting them. From a power point of view only the stoping and
starting of data transfer should make any difference.
- That said should be no problem with opening and closing streams as often
as you like. It seems most likely that if there's an issue here it's
due to a race condition somewhere or other, quite possibly in the
driver code.
> pcm opening and closing. I also noticed a few points in the alsa-lib code
> where dynamic memory is being allocated and freed and am wondering how this
> would affect heap fragmentation in the long term.
Obviously any dynamic memory allocator will be designed to deal with
frequent allocations and frees. I would be astonished if this caused a
serious issue.
> So the pre-powerdown event should occur when no sound is being played? When you
> say stop the data flowing, you mean within the sound kernel module? There is
> no call that I need to make to alsa-lib (for example making a call to
> snd_pcm_pause())? It sounds like something is not working correctly in the kernel
> module...
Just stop playing data from your application. For PCM streams from the
CPU that's all your application should need to do.
What is your actual problem here?
next prev parent reply other threads:[~2011-01-26 18:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-25 16:53 Triggering a DAPM widget event Harrod, John
2011-01-26 16:53 ` Mark Brown
2011-01-26 18:08 ` Harrod, John
2011-01-26 18:27 ` Mark Brown [this message]
2011-01-26 20:38 ` Harrod, John
2011-01-26 20:43 ` Mark Brown
2011-01-27 7:09 ` Peter Ujfalusi
2011-01-27 9:56 ` Mark Brown
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