I have a card SigmaTel STAC9221D A2 embedded in my Intel motherboard
The full ALSA info is in uploaded to general pastebin - root - post number 1016655
I am running Fedora Core 5 (Bordeaux) with kernel 2.6.18-1.2257_FC5smp

I have sound when playing a file or CD with XMMS.
I can also play what comes in through the Line-In,
using the following command line:
arecord -D hw:1,0,0 -f S16_LE -c2 -r48000 | aplay -D hw:1 &
(why in heck should I need to use the command line?!)

Anyways, these facts show that the driver works, that the
connections are ok and that the volumes are set correctly, nothing
muted, etc.

Now if I play something with XMMS, then I want to mix-in the input
from the Line-In, the command line above gives me this error:
aplay: main:564: audio open error: Device or resource busy

If I issue the command line first, and then try to play something with
XMMS I get a popup telling me about the same: sound device busy.

Now, I know that the card can do the mix, because the experiment
works just fine in Windows on the same machine.

Is there some writeup about how to config ALSA or the mixer
or the whatever so that I can get both inputs (PCM and Line-In)
to play/record simultaneously, i.e. get the mixer to mix?.
I couldn't find one.

Also, I read in this article:
LCG - How to use the snd-hda-intel module
about a few setups that helped greatly to get me as far as I got.
But the article mentions two (2) ADCs on this card/chip. However,
even the (working) Windows setup doesn't let me check 2 inputs in the
Recording Control panel at the same time, i.e. Microphone and Line-In.
Is this a bug in the Windows panel, can ALSA do better, or the info
in that page is plain wrong and this chip can't have 2 inputs active
at the same time (i.e. it has only one ADC).

Thanks for any pointers or comments.