ALSA: dice: add MIDI ports according to current number of MIDI substreams

This commit changes the way to add ALSA MIDI ports. This driver read the
number of multiplexed MIDI substreams from hardware register, then adds the
same number of ALSA MIDI ports. This commit is based on my assumption that
the number is fixed at all of supported sampling transfer frequency.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/dice/dice-midi.c

@@ -103,16 +103,27 @@ static void set_midi_substream_names(struct snd_dice *dice,
 
 int snd_dice_create_midi(struct snd_dice *dice)
 {
+	__be32 reg;
 	struct snd_rawmidi *rmidi;
 	struct snd_rawmidi_str *str;
-	unsigned int i, midi_in_ports, midi_out_ports;
+	unsigned int midi_in_ports, midi_out_ports;
 	int err;
 
-	midi_in_ports = midi_out_ports = 0;
-	for (i = 0; i < 3; i++) {
-		midi_in_ports = max(dice->tx_midi_ports[i], midi_in_ports);
-		midi_out_ports = max(dice->rx_midi_ports[i], midi_out_ports);
-	}
+	/*
+	 * Use the number of MIDI conformant data channel at current sampling
+	 * transfer frequency.
+	 */
+	err = snd_dice_transaction_read_tx(dice, TX_NUMBER_MIDI,
+					   &reg, sizeof(reg));
+	if (err < 0)
+		return err;
+	midi_in_ports = be32_to_cpu(reg);
+
+	err = snd_dice_transaction_read_rx(dice, RX_NUMBER_MIDI,
+					   &reg, sizeof(reg));
+	if (err < 0)
+		return err;
+	midi_out_ports = be32_to_cpu(reg);
 
 	if (midi_in_ports + midi_out_ports == 0)
 		return 0;