SB 3DSE ioctl() patch

[A. Wik]

On Sun, 14 Aug 2005, Julian Elischer wrote:

> Alexander Leidinger wrote:
> > On Sat, 13 Aug 2005 13:57:53 -0700
> > Julian Elischer <julian at elischer.org> wrote:
> > 
> > 
> > ---snip---
> > % man -k mixer
> > mixer(8)                 - set/display soundcard mixer values
> > ---snip---
> > 
> > For me the mixer is a device which controls the volume level of various
> > streams and is responsible how to mix those streams into each other.
> > The mixer(8) program is a program which allows to manipulate the mixer
> > (let's compare it with network routing and bandwith management).
> > 
> > The sndctrl program would be responsible to query and change various
> > properties/capabilities of the soundsystem (let's compare it with
> > configuring a network interface with ifconfig) which don't have to be
> > related to the mixer, e.g. Ariff is working on "slave-channels", which
> > decouple the hardware buffer from the userland buffer. ATM
> > slave-channels are controled by a sysctl like the vchans. This could be
> > changed to be controled by sndctl. I don't think this falls into the
> > responsibility of mixer(8).
> > 
> > What are the arguments to integrate it into mixer(8)?
> 
> one stop shopping?
> no new program to learn?

I looked at mixer(8) while exploring the the sound driver
architecture, to determine how to add the 3DSE ioctl().
However, I could not find an easy way to fit it into
either the existing mixer driver, or the userland mixer
control program.  I suppose that it might have been
possible by using typecasts and having the 3DSE feature
masquerade as a mixer input/output line, but doing it
the way I did seemed like a better choice - perhaps the
main advantage being compatibility, allowing applications
such as XMMS to use the same interface for Linux and
FreeBSD.

The standalone utility to control the feature is
a quick but functional test program.  I see one logical
reason for integrating its functionality into mixer(8):
the fact that the ioctls are done on the /dev/mixer
device (and at the hardware level, by manipulation of
Sound Blaster "mixer" registers).

In any case, the patch has been updated with an
"AGC" (Automatic Gain Control) ioctl() - also added
by the Linux driver to the "base" OSS driver, from
which both the FreeBSD and Linux Sound Blaster have
been derived at some point.

-aw