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, 10 insertions, 2 deletions

diff --git a/sound/firewire/digi00x/digi00x-hwdep.c b/sound/firewire/digi00x/digi00x-hwdep.c
index d629e415dc8b..f188e4758fd2 100644
--- a/sound/firewire/digi00x/digi00x-hwdep.c
+++ b/sound/firewire/digi00x/digi00x-hwdep.c
@@ -12,6 +12,7 @@
  * 1.get firewire node information
  * 2.get notification about starting/stopping stream
  * 3.lock/unlock stream
+ * 4.get asynchronous messaging
  */
 
 #include "digi00x.h"
@@ -25,7 +26,7 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf,  long count,
 
 	spin_lock_irq(&dg00x->lock);
 
-	while (!dg00x->dev_lock_changed) {
+	while (!dg00x->dev_lock_changed && dg00x->msg == 0) {
 		prepare_to_wait(&dg00x->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
 		spin_unlock_irq(&dg00x->lock);
 		schedule();
@@ -42,6 +43,13 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf,  long count,
 		dg00x->dev_lock_changed = false;
 
 		count = min_t(long, count, sizeof(event.lock_status));
+	} else {
+		event.digi00x_message.type =
+					SNDRV_FIREWIRE_EVENT_DIGI00X_MESSAGE;
+		event.digi00x_message.message = dg00x->msg;
+		dg00x->msg = 0;
+
+		count = min_t(long, count, sizeof(event.digi00x_message));
 	}
 
 	spin_unlock_irq(&dg00x->lock);
@@ -61,7 +69,7 @@ static unsigned int hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
 	poll_wait(file, &dg00x->hwdep_wait, wait);
 
 	spin_lock_irq(&dg00x->lock);
-	if (dg00x->dev_lock_changed)
+	if (dg00x->dev_lock_changed || dg00x->msg)
 		events = POLLIN | POLLRDNORM;
 	else
 		events = 0;