Re: documentation - yeah right!

[Takashi Iwai <tiwai@suse.de>]

At Thu, 22 May 2003 10:18:23 -0400,
Richard Cochran wrote:
> 
> I have two additional questions:
> 
> On Thu, May 22, 2003 at 02:47:27PM +0200, Takashi Iwai wrote:
> > - ALSA is not only the driver.
> > - ALSA model is still Unix style (somehow).
> > - ALSA library is the low-level library.
> 
> Are the calls snd_pcm_* kernel calls or library calls?

they are library calls.

> If the latter,
> where is the library-kernel API?
 
this is not documented.
and you should not communicate directly with the drivers.

the kernel API might be changed in future because of further
extensions.  in that case, the alsa-lib will absorb the change of
kernel API, so that the ALSA library API keeps unchanged.

hence, it's not necessary for audio application programmers to know
the kernel API (except for the curiosity :)


btw, i forgot to mention that there are some slides of my talk in LAD
meeting:
	http://www.alsa-project.org/~iwai/lad2003/lad.html


> When using the Alsa OSS compatibility layer, is there a performace
> penalty in terms of latency?

usually, no.

> Will OSS support likely be dropped in kernel 2.6?

no.  very unlikely.

> How are the OSS drivers "thread unsafe", or rather, what are the
> thready safety issues that Alsa addresses?

well, i don't think the OSS drivers are "thread unsafe" but might be
SMP unsafe or ineffective.  some OSS drivers are written on the
assumption of UP (and some are not).

ALSA has the common middle layer, and it is written carefuly to
support SMP systems.


ciao,

Takashi


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