ALSA: usb-audio: Simplify parse_audio_unit()

Minor code refactoring by combining the UAC version and the type in
the switch-case flow, so that we reduce the indentation and
redundancy.  One good bonus is that the duplicated definition of the
same type value (e.g. UAC2_EFFECT_UNIT) can be handled more cleanly.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer.c

@@ -2782,62 +2782,45 @@ static int parse_audio_unit(struct mixer_build *state, int unitid)
 		return 0; /* skip invalid unit */
 	}
 
-	if (protocol == UAC_VERSION_1 || protocol == UAC_VERSION_2) {
-		switch (p1[2]) {
-		case UAC_INPUT_TERMINAL:
-			return parse_audio_input_terminal(state, unitid, p1);
-		case UAC_MIXER_UNIT:
-			return parse_audio_mixer_unit(state, unitid, p1);
-		case UAC2_CLOCK_SOURCE:
-			return parse_clock_source_unit(state, unitid, p1);
-		case UAC_SELECTOR_UNIT:
-		case UAC2_CLOCK_SELECTOR:
-			return parse_audio_selector_unit(state, unitid, p1);
-		case UAC_FEATURE_UNIT:
-			return parse_audio_feature_unit(state, unitid, p1);
-		case UAC1_PROCESSING_UNIT:
-		/*   UAC2_EFFECT_UNIT has the same value */
-			if (protocol == UAC_VERSION_1)
-				return parse_audio_processing_unit(state, unitid, p1);
-			else
-				return 0; /* FIXME - effect units not implemented yet */
-		case UAC1_EXTENSION_UNIT:
-		/*   UAC2_PROCESSING_UNIT_V2 has the same value */
-			if (protocol == UAC_VERSION_1)
-				return parse_audio_extension_unit(state, unitid, p1);
-			else /* UAC_VERSION_2 */
-				return parse_audio_processing_unit(state, unitid, p1);
-		case UAC2_EXTENSION_UNIT_V2:
-			return parse_audio_extension_unit(state, unitid, p1);
-		default:
-			usb_audio_err(state->chip,
-				"unit %u: unexpected type 0x%02x\n", unitid, p1[2]);
-			return -EINVAL;
-		}
-	} else { /* UAC_VERSION_3 */
-		switch (p1[2]) {
-		case UAC_INPUT_TERMINAL:
-			return parse_audio_input_terminal(state, unitid, p1);
-		case UAC3_MIXER_UNIT:
-			return parse_audio_mixer_unit(state, unitid, p1);
-		case UAC3_CLOCK_SOURCE:
-			return parse_clock_source_unit(state, unitid, p1);
-		case UAC3_SELECTOR_UNIT:
-		case UAC3_CLOCK_SELECTOR:
-			return parse_audio_selector_unit(state, unitid, p1);
-		case UAC3_FEATURE_UNIT:
-			return parse_audio_feature_unit(state, unitid, p1);
-		case UAC3_EFFECT_UNIT:
-			return 0; /* FIXME - effect units not implemented yet */
-		case UAC3_PROCESSING_UNIT:
-			return parse_audio_processing_unit(state, unitid, p1);
-		case UAC3_EXTENSION_UNIT:
-			return parse_audio_extension_unit(state, unitid, p1);
-		default:
-			usb_audio_err(state->chip,
-				"unit %u: unexpected type 0x%02x\n", unitid, p1[2]);
-			return -EINVAL;
-		}
+#define PTYPE(a, b)	((a) << 8 | (b))
+	switch (PTYPE(protocol, p1[2])) {
+	case PTYPE(UAC_VERSION_1, UAC_INPUT_TERMINAL):
+	case PTYPE(UAC_VERSION_2, UAC_INPUT_TERMINAL):
+	case PTYPE(UAC_VERSION_3, UAC_INPUT_TERMINAL):
+		return parse_audio_input_terminal(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC_MIXER_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC_MIXER_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_MIXER_UNIT):
+		return parse_audio_mixer_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_2, UAC2_CLOCK_SOURCE):
+	case PTYPE(UAC_VERSION_3, UAC3_CLOCK_SOURCE):
+		return parse_clock_source_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC_SELECTOR_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC_SELECTOR_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_SELECTOR_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC2_CLOCK_SELECTOR):
+	case PTYPE(UAC_VERSION_3, UAC3_CLOCK_SELECTOR):
+		return parse_audio_selector_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC_FEATURE_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC_FEATURE_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_FEATURE_UNIT):
+		return parse_audio_feature_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC1_PROCESSING_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC2_PROCESSING_UNIT_V2):
+	case PTYPE(UAC_VERSION_3, UAC3_PROCESSING_UNIT):
+		return parse_audio_processing_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_1, UAC1_EXTENSION_UNIT):
+	case PTYPE(UAC_VERSION_2, UAC2_EXTENSION_UNIT_V2):
+	case PTYPE(UAC_VERSION_3, UAC3_EXTENSION_UNIT):
+		return parse_audio_extension_unit(state, unitid, p1);
+	case PTYPE(UAC_VERSION_2, UAC2_EFFECT_UNIT):
+	case PTYPE(UAC_VERSION_3, UAC3_EFFECT_UNIT):
+		return 0; /* FIXME - effect units not implemented yet */
+	default:
+		usb_audio_err(state->chip,
+			      "unit %u: unexpected type 0x%02x\n",
+			      unitid, p1[2]);
+		return -EINVAL;
 	}
 }