ALSA: firewire-digi00x: add support of asynchronous transaction for outgoing MIDI messages to physical controls

In previous commit, asynchronous transaction for incoming MIDI messages
from physical controls is supported. The physical controls may be
controlled by receiving MIDI messages at a certain address.

This commit supports asynchronous transaction for this purpose.

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

sound/firewire/digi00x/digi00x-transaction.c

@@ -9,6 +9,18 @@
 #include <sound/asound.h>
 #include "digi00x.h"
 
+static int fill_midi_message(struct snd_rawmidi_substream *substream, u8 *buf)
+{
+	int bytes;
+
+	buf[0] = 0x80;
+	bytes = snd_rawmidi_transmit_peek(substream, buf + 1, 2);
+	if (bytes >= 0)
+		buf[3] = 0xc0 | bytes;
+
+	return bytes;
+}
+
 static void handle_midi_control(struct snd_dg00x *dg00x, __be32 *buf,
 				unsigned int length)
 {
@@ -102,15 +114,24 @@ int snd_dg00x_transaction_register(struct snd_dg00x *dg00x)
 		return err;
 
 	err = snd_dg00x_transaction_reregister(dg00x);
-	if (err < 0) {
-		fw_core_remove_address_handler(&dg00x->async_handler);
-		dg00x->async_handler.address_callback = NULL;
-	}
+	if (err < 0)
+		goto error;
 
+	err = snd_fw_async_midi_port_init(&dg00x->out_control, dg00x->unit,
+					  DG00X_ADDR_BASE + DG00X_OFFSET_MMC,
+					  4, fill_midi_message);
+	if (err < 0)
+		goto error;
+
+	return err;
+error:
+	fw_core_remove_address_handler(&dg00x->async_handler);
+	dg00x->async_handler.address_callback = NULL;
 	return err;
 }
 
 void snd_dg00x_transaction_unregister(struct snd_dg00x *dg00x)
 {
+	snd_fw_async_midi_port_destroy(&dg00x->out_control);
 	fw_core_remove_address_handler(&dg00x->async_handler);
 }

sound/firewire/digi00x/digi00x.h

@@ -56,6 +56,7 @@ struct snd_dg00x {
 
 	/* For asynchronous MIDI controls. */
 	struct snd_rawmidi_substream *in_control;
+	struct snd_fw_async_midi_port out_control;
 };
 
 #define DG00X_ADDR_BASE		0xffffe0000000ull