From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takashi Iwai <tiwai@suse.de>
Subject: Re: DMIX and capture stream
Date: Wed, 07 Jan 2004 16:02:02 +0100
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To: Abramo Bagnara <abramo.bagnara@tin.it>
Cc: Florian Schmidt <mista.tapas@gmx.net>, alsa-devel@lists.sourceforge.net
List-Id: alsa-devel@alsa-project.org

At Wed, 07 Jan 2004 15:39:14 +0100,
Abramo Bagnara wrote:
> 
> Takashi Iwai wrote:
> > At Wed, 07 Jan 2004 13:45:05 +0100,
> > Abramo Bagnara wrote:
> > 
> >>Takashi Iwai wrote:
> >>
> >>
> >>>as written in my previous mail, it was a quick hack.  and there is a
> >>>better approach.
> >>
> >>I'd prefer the following approach:
> >>
> >>pcmp.duplex {
> >>	type dmix
> >>	...
> >>}
> >>
> >>pcmc.duplex {
> >>	type dsnoop
> >>	...
> >>}
> >>
> >>with the following policy:
> >>- if capture is specified pcmc and pcm are searched in this order
> >>- if playback is specified pcmp and pcm are searched in this order
> > 
> > 
> > this was my first idea, too.
> > 
> > but i'm afraid that it will lead to more conditionals (i.e. more
> > codes) over all plugins with a slave pcm, and make the syntax more
> > complicated.
> 
> I don't see your point, can you show me an example of what you mean?
> 
> AFAICS the only code that need to be changed is the PCM definition lookup.

there are two parts to be modified, snd_pcm_open_noupdate() and
snd_pcm_slave_conf().  they are the parts which look up "pcm"
directive in the configuration.
the former is easy.  but the latter function doesn't have stream
argument, so it cannot check whether "pcmp" or "pcmc" to check.  and,
changing this function will need rewriting all callers...


Takashi


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