ALSA: firewire-tascam: fix loop condition with some readable variables

In transactions for MIDI messages, the first byte is used for label and
the rest is for MIDI bytes. In current code, these are handled correctly,
while there's a small mistake for loop condition to include meaningless
statement.

This commit adds two local variables for them and improve the loop
condition.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/tascam/tascam-transaction.c

@@ -63,17 +63,22 @@ static int fill_message(struct snd_rawmidi_substream *substream, u8 *buf)
 	struct snd_tscm *tscm = substream->rmidi->private_data;
 	unsigned int port = substream->number;
 	int i, len, consume;
+	u8 *label, *msg;
 	u8 status;
 
-	consume = snd_rawmidi_transmit_peek(substream, buf + 1, 3);
+	/* The first byte is used for label, the rest for MIDI bytes. */
+	label = buf;
+	msg = buf + 1;
+
+	consume = snd_rawmidi_transmit_peek(substream, msg, 3);
 	if (consume == 0)
 		return 0;
 
 	/* On exclusive message. */
 	if (tscm->on_sysex[port]) {
 		/* Seek the end of exclusives. */
-		for (i = 1; i < 4 || i < consume; ++i) {
-			if (buf[i] == 0xf7) {
+		for (i = 0; i < consume; ++i) {
+			if (msg[i] == 0xf7) {
 				tscm->on_sysex[port] = false;
 				break;
 			}
@@ -81,27 +86,27 @@ static int fill_message(struct snd_rawmidi_substream *substream, u8 *buf)
 
 		/* At the end of exclusive message, use label 0x07. */
 		if (!tscm->on_sysex[port]) {
-			consume = i;
-			buf[0] = (port << 4) | 0x07;
+			consume = i + 1;
+			*label = (port << 4) | 0x07;
 		/* During exclusive message, use label 0x04. */
 		} else if (consume == 3) {
-			buf[0] = (port << 4) | 0x04;
+			*label = (port << 4) | 0x04;
 		/* We need to fill whole 3 bytes. Go to next change. */
 		} else {
 			consume = 0;
 		}
 	} else {
 		/* The beginning of exclusives. */
-		if (buf[1] == 0xf0) {
+		if (msg[0] == 0xf0) {
 			/* Transfer it in next chance in another condition. */
 			tscm->on_sysex[port] = true;
 			return 0;
 		} else {
 			/* On running-status. */
-			if ((buf[1] & 0x80) != 0x80)
+			if ((msg[0] & 0x80) != 0x80)
 				status = tscm->running_status[port];
 			else
-				status = buf[1];
+				status = msg[0];
 
 			/* Calculate consume bytes. */
 			len = calculate_message_bytes(status);
@@ -109,13 +114,13 @@ static int fill_message(struct snd_rawmidi_substream *substream, u8 *buf)
 				return 0;
 
 			/* On running-status. */
-			if ((buf[1] & 0x80) != 0x80) {
-				buf[3] = buf[2];
-				buf[2] = buf[1];
-				buf[1] = tscm->running_status[port];
+			if ((msg[0] & 0x80) != 0x80) {
+				msg[2] = msg[1];
+				msg[1] = msg[0];
+				msg[0] = tscm->running_status[port];
 				consume--;
 			} else {
-				tscm->running_status[port] = buf[1];
+				tscm->running_status[port] = msg[0];
 			}
 
 			/* Confirm length. */
@@ -125,7 +130,7 @@ static int fill_message(struct snd_rawmidi_substream *substream, u8 *buf)
 				consume = len;
 		}
 
-		buf[0] = (port << 4) | (buf[1] >> 4);
+		*label = (port << 4) | (msg[0] >> 4);
 	}
 
 	return consume;