I'm still learning a lot about this specification and driver, so I can
only be of limited help on this:

The STAC9220 by default has an absurdly low output volume.  The
FreeBSD driver has a fixup for this.  I have a STAC9221, and it has
the same problem.

http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/dev/sound/pci/hda/hdac.c?rev=1.24&content-type=text/x-cvsweb-markup

Search for 'softpcm' in the file to see the relevant bits.  The code
that does the work is this:

	/*
		 * XXX Temporary quirk for STAC9220, until the parser
		 *     become smarter.
		 */
		if (id == HDA_CODEC_STAC9220) {
			mask |= SOUND_MASK_VOLUME;
			while ((ctl = hdac_audio_ctl_each(devinfo, &i)) !=
			    NULL) {
				if (ctl->widget == NULL || ctl->enable == 0)
					continue;
				if (ctl->widget->nid == 11 && ctl->index == 0) {
					ctl->ossmask = SOUND_MASK_VOLUME;
					ctl->ossval = 100 | (100 << 8);
				} else
					ctl->ossmask &= ~SOUND_MASK_VOLUME;
			}
		} else if (id == HDA_CODEC_STAC9221) {
			mask |= SOUND_MASK_VOLUME;
			while ((ctl = hdac_audio_ctl_each(devinfo, &i)) !=
			    NULL) {
				if (ctl->widget == NULL)
					continue;
				if (ctl->widget->nid == 2 && ctl->index == 0) {
					ctl->enable = 1;
					ctl->ossmask = SOUND_MASK_VOLUME;
					ctl->ossval = 100 | (100 << 8);
				} else if (ctl->enable == 0)
					continue;
				else
					ctl->ossmask &= ~SOUND_MASK_VOLUME;
			}
		} else {
			mix_setparentchild(m, SOUND_MIXER_VOLUME,
			    SOUND_MASK_PCM);
			if (!(mask & SOUND_MASK_VOLUME))
				mix_setrealdev(m, SOUND_MIXER_VOLUME,
				    SOUND_MIXER_NONE);
			while ((ctl = hdac_audio_ctl_each(devinfo, &i)) !=
			    NULL) {
				if (ctl->widget == NULL || ctl->enable == 0)
					continue;
				if (!HDA_FLAG_MATCH(ctl->ossmask,
				    SOUND_MASK_VOLUME | SOUND_MASK_PCM))
					continue;
				if (!(ctl->mute == 1 && ctl->step == 0))
					ctl->enable = 0;
			}
		}
	}

I guess what it does is iterate through the volume widgets and crank them up. ;)
I don't have the time right now to look into this more, but I thought
I'd just put this out there
if anyone had any comments (or an idea of how to implement this for our driver).

I am also trying to figure out how to implement mmap support; my audio
skips too much!

Regards,

--Blair

-- 
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"The frivolity and boredom which unsettle the established order, the
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approaching change.  The gradual crumbling that left unaltered the the
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illuminates the features of the new world."  --G.W.F. Hegel,
_Phenomenology of Spirit_ 5:11