PATCH: creating devices for multiple sound cards

PATCH: creating devices for multiple sound cards

[Chris Rankin]

Hi,
I have just installed a new sound card in my machine, and have left
the built-in sound chip enabled despite the motherboard manufacturer's
warning of Bad Things. The result is that I now have two sound devices
in my machine - an ICH (i810_audio) and a Soundblaster Live! The Live!
is device 0, of course. Anyway, I am using the ALSA drivers because
the native i810_audio module caused a kernel panic (NULL pointer
reference in an interrupt handler, I believe), and I have noticed that
the ALSA drivers have difficulty creating OSS device nodes for both
cards. I have traced the problem to the register_sound_special()
function within Linux's soundcore.o module. Basically, ALSA uses this
function to create OSS devices, but this function was never written
with more than one sound device in mind. Until now.

A few points about this patch:

1. I have renamed "sequencer2" to "music" because of a potential naming
conflict between devices 14,8 ("music" on card 0) and 14,33 ("sequencer"
on card 2).

2. I have renamed device "midi00" to "midi". "midi01" now becomes "midi1"
as well, although I would also point out that this is now consistent with
the behaviour of the register_sound_midi() function.

Having applied this patch, ALSA gives me two mixer devices in /dev/sound,
and I no longer get messages like these in my logs:

Apr 12 01:36:54 (none) kernel: devfs: devfs_register(): device already registered: "unknown"

Apr 12 01:40:04 (none) kernel: devfs: devfs_register(): device already registered: "mixer"
Apr 12 01:40:04 (none) kernel: devfs: devfs_register(): device already registered: "dsp"

Cheers,
Chris

--- linux-2.4.3/drivers/sound/sound_core.c.orig	Fri Mar 16 23:00:44 2001
+++ linux-2.4.3/drivers/sound/sound_core.c	Sat Apr 14 00:13:18 2001
@@ -227,9 +227,10 @@
  
 int register_sound_special(struct file_operations *fops, int unit)
 {
-	char *name;
+	const char *name;
+	const int minor = (unit & 15);
 
-	switch (unit) {
+	switch (minor) {
 	    case 0:
 		name = "mixer";
 		break;
@@ -237,7 +238,7 @@
 		name = "sequencer";
 		break;
 	    case 2:
-		name = "midi00";
+		name = "midi";
 		break;
 	    case 3:
 		name = "dsp";
@@ -255,7 +256,7 @@
 		name = "unknown7";
 		break;
 	    case 8:
-		name = "sequencer2";
+		name = "music";
 		break;
 	    case 9:
 		name = "dmmidi";
@@ -279,7 +280,7 @@
 		name = "unknown";
 		break;
 	}
-	return sound_insert_unit(&chains[unit&15], fops, -1, unit, unit+1,
+	return sound_insert_unit(&chains[minor], fops, -1, minor, minor+128,
 				 name, S_IRUSR | S_IWUSR);
 }
  
-
To unsubscribe from this list: send the line "unsubscribe linux-sound" in
the body of a message to majordomo@vger.kernel.org