Hi Takashi.

I noticed on 2.6.16-rc4 that my MPU-401 wasn't functional, due to a 
simple copy & paste error in sound/isa/cs423x/cs4236.c:

Index: local/sound/isa/cs423x/cs4236.c
===================================================================
--- local.orig/sound/isa/cs423x/cs4236.c        2006-02-11 
00:34:12.000000000 +0100
+++ local/sound/isa/cs423x/cs4236.c     2006-02-20 04:01:29.000000000 +0100
@@ -414,7 +414,7 @@ static int __devinit snd_card_cs423x_pnp
         }
         /* MPU initialization */
         if (acard->mpu && mpu_port[dev] > 0) {
-               if (snd_cs423x_pnp_init_mpu(dev, acard->ctrl, cfg) < 0)
+               if (snd_cs423x_pnp_init_mpu(dev, acard->mpu, cfg) < 0)
                         goto error;
         }
         kfree(cfg);

Please apply. However, when I tested it (mpu works fine again after 
this) I noticed that modprobe -r snd-cs4236 didn't release things -- 
specifically that the fixed index=1 I have for the card failed on a 
subsequent modprobe since ALSA believes that index is still taken.

I stuck a few printks in cs4236.c. From "snd_cs423x_unregister_all", 
"pnp_unregister_card_driver(&cs423x_pnpc_driver)" is indeed being called 
but the card driver's own remove method, snd_cs423x_pnpc_remove, is not.

I started looking, but ran into the next issue again -- when snd-cs4236 
is not card1 but card0, modprobe -r oopses in snd_timer_free (attached) 
meaning debugging this wants someone with more of an overview of recent 
damage done^W^Wchanges made.

Given that calling pnp_unregister_card_driver() is not cs4236 specific, 
I assume the problem is more general. Possibly all ALSA ISA-PnP drivers. 
Or, given that pnp_unregister_card_driver is not an ALSA function, maybe 
even all ISA-PnP drivers using the card_driver interface.

The more general this problem turns out, the more reason there would be 
for fixing this pre 2.6.16, obviously. I can test patches...

Rene.