ALSA: usb-audio: Inform inconsistent protocols in GTBs

When parsing Group Terminal Blocks, we overwrote the preferred
protocol and the protocol capabilities silently from the last parsed
GTB.  This patch adds the information print indicating the unexpected
overrides instead of silent action.
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-17-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/midi2.c

@@ -581,6 +581,7 @@ static int parse_group_terminal_block(struct snd_usb_midi2_ump *rmidi,
 				      const struct usb_ms20_gr_trm_block_descriptor *desc)
 {
 	struct snd_ump_endpoint *ump = rmidi->ump;
+	unsigned int protocol, protocol_caps;
 
 	/* set default protocol */
 	switch (desc->bMIDIProtocol) {
@@ -588,24 +589,40 @@ static int parse_group_terminal_block(struct snd_usb_midi2_ump *rmidi,
 	case USB_MS_MIDI_PROTO_1_0_64_JRTS:
 	case USB_MS_MIDI_PROTO_1_0_128:
 	case USB_MS_MIDI_PROTO_1_0_128_JRTS:
-		ump->info.protocol = SNDRV_UMP_EP_INFO_PROTO_MIDI1;
+		protocol = SNDRV_UMP_EP_INFO_PROTO_MIDI1;
 		break;
 	case USB_MS_MIDI_PROTO_2_0:
 	case USB_MS_MIDI_PROTO_2_0_JRTS:
-		ump->info.protocol = SNDRV_UMP_EP_INFO_PROTO_MIDI2;
+		protocol = SNDRV_UMP_EP_INFO_PROTO_MIDI2;
 		break;
+	default:
+		return 0;
 	}
 
-	ump->info.protocol_caps = ump->info.protocol;
+	if (ump->info.protocol && ump->info.protocol != protocol)
+		usb_audio_info(rmidi->umidi->chip,
+			       "Overriding preferred MIDI protocol in GTB %d: %x -> %x\n",
+			       rmidi->usb_block_id, ump->info.protocol,
+			       protocol);
+	ump->info.protocol = protocol;
+
+	protocol_caps = protocol;
 	switch (desc->bMIDIProtocol) {
 	case USB_MS_MIDI_PROTO_1_0_64_JRTS:
 	case USB_MS_MIDI_PROTO_1_0_128_JRTS:
 	case USB_MS_MIDI_PROTO_2_0_JRTS:
-		ump->info.protocol_caps |= SNDRV_UMP_EP_INFO_PROTO_JRTS_TX |
+		protocol_caps |= SNDRV_UMP_EP_INFO_PROTO_JRTS_TX |
 			SNDRV_UMP_EP_INFO_PROTO_JRTS_RX;
 		break;
 	}
 
+	if (ump->info.protocol_caps && ump->info.protocol_caps != protocol_caps)
+		usb_audio_info(rmidi->umidi->chip,
+			       "Overriding MIDI protocol caps in GTB %d: %x -> %x\n",
+			       rmidi->usb_block_id, ump->info.protocol_caps,
+			       protocol_caps);
+	ump->info.protocol_caps = protocol_caps;
+
 	return 0;
 }