ALSA: firewire-digi00x: add support for asynchronous messaging

Digi 002/003 family uses asynchronous transaction for messaging.
The address to transmit this message is stored on a certain register.

This commit allocates a range of address on OHCI 1394 host controller
to handle the messaging. As long as I know, the purpose of this message
seems to notify lost of synchronization. While, the meaning of content
of the message is not clear.

Actual examples of this messaging:
 * When clock source is set as internal:
 - 0x00007051
 - 0x00007052
 - 0x00007054
 - 0x00007057
 - 0x00007058
 * When clock source is set as somewhat external:
 - 0x00009000
 - 0x00009010
 - 0x00009020
 - 0x00009021
 - 0x00009022

The lost often occurs when using internal clock source. In this case,
users hear sounds with quite short gap every several minutes. In fact,
the lost is recovered temporarily.

When using with external clock source, the lost seems not to occur. The
mechanism is not clear yet.

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

1 files changed, 7 insertions, 0 deletions

diff --git a/include/uapi/sound/firewire.h b/include/uapi/sound/firewire.h
index f67d228..deb041c 100644
--- a/include/uapi/sound/firewire.h
+++ b/include/uapi/sound/firewire.h
@@ -9,6 +9,7 @@
 #define SNDRV_FIREWIRE_EVENT_LOCK_STATUS	0x000010cc
 #define SNDRV_FIREWIRE_EVENT_DICE_NOTIFICATION	0xd1ce004e
 #define SNDRV_FIREWIRE_EVENT_EFW_RESPONSE	0x4e617475
+#define SNDRV_FIREWIRE_EVENT_DIGI00X_MESSAGE	0x746e736c
 
 struct snd_firewire_event_common {
 	unsigned int type; /* SNDRV_FIREWIRE_EVENT_xxx */
@@ -40,11 +41,17 @@ struct snd_firewire_event_efw_response {
 	__be32 response[0];	/* some responses */
 };
 
+struct snd_firewire_event_digi00x_message {
+	unsigned int type;
+	__u32 message;	/* Digi00x-specific message */
+};
+
 union snd_firewire_event {
 	struct snd_firewire_event_common            common;
 	struct snd_firewire_event_lock_status       lock_status;
 	struct snd_firewire_event_dice_notification dice_notification;
 	struct snd_firewire_event_efw_response      efw_response;
+	struct snd_firewire_event_digi00x_message   digi00x_message;
 };