[alsa-devel] [regression] probably in mixer.c code

[Takashi Iwai]

At Tue, 08 Nov 2011 09:49:13 +0100,
Alexey Fisher wrote:
> 
> Hallo all, Takashi,
> 
> there is one regression in current linux main tree:
> 
> cval->res quirks do not work any more. See usb/mixer.c:1150
> Are there was some work in this area or may be some one bisected this 
> bug down?

Are you referring to the device 046d:09a4, which sets the mixer range
manually?  If yes, does the patch below work?


Takashi

---
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 60f65ac..92feff1 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -765,6 +765,28 @@ static void usb_mixer_elem_free(struct snd_kcontrol *kctl)
  * interface to ALSA control for feature/mixer units
  */
 
+/* convert from USB descriptions to dB scale
+ * USB descriptions contain the dB scale in 1/256 dB unit
+ * while ALSA TLV contains in 1/100 dB unit
+ */
+static int convert_cval_to_dB(struct usb_mixer_elem_info *cval)
+{
+	cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;
+	cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;
+	if (cval->dBmin > cval->dBmax) {
+		/* something is wrong; assume it's either from/to 0dB */
+		if (cval->dBmin < 0)
+			cval->dBmax = 0;
+		else if (cval->dBmin > 0)
+			cval->dBmin = 0;
+		if (cval->dBmin > cval->dBmax) {
+			/* totally crap, return an error */
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
 /*
  * retrieve the minimum and maximum values for the specified control
  */
@@ -844,24 +866,7 @@ static int get_min_max(struct usb_mixer_elem_info *cval, int default_min)
 		cval->initialized = 1;
 	}
 
-	/* USB descriptions contain the dB scale in 1/256 dB unit
-	 * while ALSA TLV contains in 1/100 dB unit
-	 */
-	cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;
-	cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;
-	if (cval->dBmin > cval->dBmax) {
-		/* something is wrong; assume it's either from/to 0dB */
-		if (cval->dBmin < 0)
-			cval->dBmax = 0;
-		else if (cval->dBmin > 0)
-			cval->dBmin = 0;
-		if (cval->dBmin > cval->dBmax) {
-			/* totally crap, return an error */
-			return -EINVAL;
-		}
-	}
-
-	return 0;
+	return convert_cval_to_dB(cval);
 }
 
 
@@ -1134,6 +1139,7 @@ static void build_feature_ctl(struct mixer_build *state, void *raw_desc,
 			snd_printk(KERN_INFO
 				 "set volume quirk for UDA1321/N101 chip\n");
 			cval->max = -256;
+			convert_cval_to_dB(cval);
 		}
 		break;
 
@@ -1144,6 +1150,8 @@ static void build_feature_ctl(struct mixer_build *state, void *raw_desc,
 			cval->min = 6080;
 			cval->max = 8768;
 			cval->res = 192;
+			cval->initialized = 1;
+			convert_cval_to_dB(cval);
 		}
 		break;