ALSA: usb-audio: Parse UMP Endpoint and Function Blocks at first

Try to parse the UMP Endpoint and UMP Function Blocks for building the
topology at first.  Only when those are missing (e.g. on an older USB
MIDI 2.0 spec or a unidirectional endpoint), the driver still creates
blocks based on USB group terminal block information as fallback.

Link: https://lore.kernel.org/r/20230612081054.17200-4-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/midi2.c

@@ -80,6 +80,7 @@ struct snd_usb_midi2_ump {
 	struct snd_usb_midi2_endpoint *eps[2];	/* USB MIDI endpoints */
 	int index;				/* rawmidi device index */
 	unsigned char usb_block_id;		/* USB GTB id used for finding a pair */
+	bool ump_parsed;			/* Parsed UMP 1.1 EP/FB info*/
 	struct list_head list;		/* list to umidi->rawmidi_list */
 };
 
@@ -786,6 +787,31 @@ static int find_matching_ep_partner(struct snd_usb_midi2_interface *umidi,
 	return 0;
 }
 
+/* Call UMP helper to parse UMP endpoints;
+ * this needs to be called after starting the input streams for bi-directional
+ * communications
+ */
+static int parse_ump_endpoints(struct snd_usb_midi2_interface *umidi)
+{
+	struct snd_usb_midi2_ump *rmidi;
+	int err;
+
+	list_for_each_entry(rmidi, &umidi->rawmidi_list, list) {
+		if (!rmidi->ump ||
+		    !(rmidi->ump->core.info_flags & SNDRV_RAWMIDI_INFO_DUPLEX))
+			continue;
+		err = snd_ump_parse_endpoint(rmidi->ump);
+		if (!err) {
+			rmidi->ump_parsed = true;
+		} else {
+			if (err == -ENOMEM)
+				return err;
+			/* fall back to GTB later */
+		}
+	}
+	return 0;
+}
+
 /* create a UMP block from a GTB entry */
 static int create_gtb_block(struct snd_usb_midi2_ump *rmidi, int dir, int blk)
 {
@@ -856,7 +882,7 @@ static int create_blocks_from_gtb(struct snd_usb_midi2_interface *umidi)
 		if (!rmidi->ump)
 			continue;
 		/* Blocks have been already created? */
-		if (rmidi->ump->info.num_blocks)
+		if (rmidi->ump_parsed || rmidi->ump->info.num_blocks)
 			continue;
 		/* loop over GTBs */
 		for (dir = 0; dir < 2; dir++) {
@@ -1110,6 +1136,12 @@ int snd_usb_midi_v2_create(struct snd_usb_audio *chip,
 		goto error;
 	}
 
+	err = parse_ump_endpoints(umidi);
+	if (err < 0) {
+		usb_audio_err(chip, "Failed to parse UMP endpoint\n");
+		goto error;
+	}
+
 	err = create_blocks_from_gtb(umidi);
 	if (err < 0) {
 		usb_audio_err(chip, "Failed to create GTB blocks\n");