kern/84728: [sound] [patch] ac97 broken mixing capabilities checking

[michaels at sdf.lonestar.org]

>Number:         84728
>Category:       kern
>Synopsis:       [sound] [patch] ac97 broken mixing capabilities checking
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Wed Aug 10 03:30:11 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Michael Seyfert
>Release:        FreeBSD 7.0-CURRENT i386
>Organization:
>Environment:
System: FreeBSD icemach.my.domain 7.0-CURRENT i386

>Description:

new sys/dev/sound/pcm/ac97.c introduces some problems with mixer
capabilities checking.
It does not properly set the "width of control field" for cards with
a non-default width. As such the volume control is misaligned ( I can
only change the volume from 50% to 100% on my audigy card.)

Also, there's an if statement and for loops that logically don't do
anything at all, which has me wondering about the quality of this code.

I think the author (Ariff Abdullah <skywizard at MyBSD.org.my>) should redo it.

>How-To-Repeat:
	Audigy 2 card...

>Fix:

Here's a patch to revert this code to the previous version.

--- sys/dev/sound/pcm/ac97.c	Sun Jul 31 08:28:31 2005
+++ /home/michael/work/ac97.c	Tue Aug  9 19:12:01 2005
@@ -611,39 +611,15 @@
 	for (i = 0; i < 32; i++) {
 		k = codec->noext? codec->mix[i].enable : 1;
 		if (k && (codec->mix[i].reg > 0)) {
-			j = old = ac97_rdcd(codec, codec->mix[i].reg);
-			if (!(j & 0x8000)) {
-				ac97_wrcd(codec, codec->mix[i].reg, j | 0x8000);
-				j = ac97_rdcd(codec, codec->mix[i].reg);
-			}
-			if ((j & 0x8000)) {
-				j = ((1 << 6) - 1) << codec->mix[i].ofs;
-				if (codec->mix[i].mute)
-					j |= 0x8000;
-				ac97_wrcd(codec, codec->mix[i].reg, j);
-				j = ac97_rdcd(codec, codec->mix[i].reg) & j;
-				j >>= codec->mix[i].ofs;
-				if (codec->mix[i].reg == AC97_MIX_TONE &&
-						((j & 0x0001) == 0x0000))
-					j >>= 1;
-				for (k = 0; j != 0; k++)
-					j >>= 1;
-				for (j = 0; k != 0; j++)
-					k >>= 1;
-				if (j != 0) {
-					codec->mix[i].enable = 1;
-#if 0
-					codec->mix[i].bits = j;
-#endif
-				} else
-					codec->mix[i].enable = 0;
-			} else
-				codec->mix[i].enable = 0;
+			old = ac97_rdcd(codec, codec->mix[i].reg);
+			ac97_wrcd(codec, codec->mix[i].reg, 0x3f);
+			j = ac97_rdcd(codec, codec->mix[i].reg);
 			ac97_wrcd(codec, codec->mix[i].reg, old);
+			codec->mix[i].enable = (j != 0 && j != old)? 1 : 0;
+			for (k = 1; j & (1 << k); k++);
+			codec->mix[i].bits = j? k - codec->mix[i].ofs : 0;
 		}
-#if 0
-		printf("mixch %d, en=%d, b=%d\n", i, codec->mix[i].enable, codec->mix[i].bits);
-#endif
+		/* printf("mixch %d, en=%d, b=%d\n", i, codec->mix[i].enable, codec->mix[i].bits); */
 	}
 
 	device_printf(codec->dev, "<%s>\n",
>Release-Note:
>Audit-Trail:
>Unformatted: