[alsa-devel] Confusing about Playback/Capture, CODEC/CODEC links, and snd_soc_dapm_link_dai_widgets()

Mark Brown broonie at opensource.wolfsonmicro.com
Fri Jun 1 23:41:47 CEST 2012

On Fri, Jun 01, 2012 at 12:37:09AM +0100, Mark Brown wrote:
> On Thu, May 31, 2012 at 04:49:26PM -0600, Stephen Warren wrote:

> > But if (2) is correct, I wonder why soc_dapm_stream_event()'s first if
> > statement appears to consider the playback_widget of both sides of the
> > DAI to be coupled; wouldn't one side's playback widget be coupled to the
> > other side's capture widget?

> The DAIs on CPUs have the opposite sense to DAIs on CODECs.  In a
> traditional CPU<->CODEC link we do connect the two playback widgets
> directly to each other.  The current code isn't correct, it's not
> normally noticable since most of the time the CPU DAI end of the link is
> a baseband which doesn't do anything real and is always activated
> bidirectionally so it really makes no odds which widget we look at.

> I'll fix this tomorrow.

Sorry, I misremembered the context here (should've looked at the code
not the quote!).  The current code is correct, it will only be used in
the case where we have a "real CPU" not the CODEC<->CODEC case so it's
doing the right thing.
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