[alsa-devel] how does hw:0, 1 eventually get mapped to /dev/snd/controlC0 and company? is this on the wiki somewhere?

John Utz John.Utz at dmx.com
Fri Mar 30 20:22:27 CEST 2007

as usual, plz forgive my poor citing.

-----Original Message-----
From: rlrevell at gmail.com on behalf of Lee Revell
Sent: Thu 3/29/2007 7:10 PM
To: John Utz
Cc: Takashi Iwai; alsa-devel at alsa-project.org
Subject: Re: [alsa-devel] how does hw:0, 1 eventually get mapped to /dev/snd/controlC0 and company? is this on the wiki somewhere?
Hello Lee;

Thankyou for taking the time to respond, i appreciate it!

On 3/29/07, John Utz <John.Utz at dmx.com> wrote:
> since i dont need a generic solution, it would be very helpful to me to not use alsa-lib and just use the alsa modules the way that our current version of the player uses /dev/dsp from the alsa oss-compat kernel modules.
> i'd like to open and playback to /dev/snd/pcmC0D0p and /dev/snd/pcmC0D1p directly if it's a reasonable thing to do.

* The alsa-lib <-> kernel interface is intentionally undocumented.  The
* only officially supported interface to ALSA is via alsa-lib.

you can still document things even if you dont support them!

most app writers will use the lib because it does a very good job of dealing with all the inscrutable mandatory details of getting sound out of an arbitrary device.

but it's not the best fit for everybody! 

what if you have a very teensy tiny filesystem and you dont want to fill your limited space with text configuration files and executable code that reads the conf files and executes test calls that you as a developer already know the answer to because you are the guy that also wrote the driver for the only hardware that you will ever use?

The lib code is in front of me and i have a compiler and a debugger and i will figure it out in the fullness of time.

Make no mistake, it will be kind of a fun adventure! 

But having fun is supposed to be just a side effect of doing a good job for my employer and to do a good job for my employer i need to meet a rather short deadline! 

Thus i am executing my responsibility as an effective employee by asking for help on this matter.

* If you really refuse to use alsa-lib (it's not that big, I've used it
* in embedded projects),

'refuse' is much too strong of a term! 

i seek to minimize:

1. the filesystem space required
2. the build complexity involved in building our product.

i have to cross-compile *everything!* and currently i am the *only* guy in the whole company that's doing this job, i wish to provide as simple a build process as possible for my future self or my windows centric coworkers.
* then just enable ALSA's OSS emulation and continue to use /dev/dsp.

does /dev/dsp support use of 4 channel output? how would one create 4 individual mono streams with /dev/dsp?

i dont think this is possible. am i mistaken?

* Lee

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