[alsa-devel] [PATCH 5/5] ALSA: firewire-tascam: notify events of change of state for userspace applications

[Takashi Sakamoto]

In former commits, ALSA firewire-tascam driver queues events to notify
change of state of control surface to userspace via ALSA hwdep
interface.

This commit implements actual notification of the events. The events are
not governed by real time, thus no need to care underrun.

Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 include/uapi/sound/firewire.h        |  7 +++
 sound/firewire/tascam/amdtp-tascam.c |  2 +
 sound/firewire/tascam/tascam-hwdep.c | 65 +++++++++++++++++++++++++++-
 3 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/include/uapi/sound/firewire.h b/include/uapi/sound/firewire.h
index bb067efb09c6..ae12826ed641 100644
--- a/include/uapi/sound/firewire.h
+++ b/include/uapi/sound/firewire.h
@@ -12,6 +12,7 @@
 #define SNDRV_FIREWIRE_EVENT_EFW_RESPONSE	0x4e617475
 #define SNDRV_FIREWIRE_EVENT_DIGI00X_MESSAGE	0x746e736c
 #define SNDRV_FIREWIRE_EVENT_MOTU_NOTIFICATION	0x64776479
+#define SNDRV_FIREWIRE_EVENT_TASCAM_CONTROL	0x7473636d
 
 struct snd_firewire_event_common {
 	unsigned int type; /* SNDRV_FIREWIRE_EVENT_xxx */
@@ -59,12 +60,18 @@ struct snd_firewire_tascam_change {
 	__be32 after;
 };
 
+struct snd_firewire_event_tascam_control {
+	unsigned int type;
+	struct snd_firewire_tascam_change changes[0];
+};
+
 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;
+	struct snd_firewire_event_tascam_control    tascam_control;
 	struct snd_firewire_event_motu_notification motu_notification;
 };
 
diff --git a/sound/firewire/tascam/amdtp-tascam.c b/sound/firewire/tascam/amdtp-tascam.c
index 0e8088c9ada9..a52d1f76c610 100644
--- a/sound/firewire/tascam/amdtp-tascam.c
+++ b/sound/firewire/tascam/amdtp-tascam.c
@@ -156,6 +156,8 @@ static void read_status_messages(struct amdtp_stream *s,
 				if (++tscm->push_pos >= SND_TSCM_QUEUE_COUNT)
 					tscm->push_pos = 0;
 				spin_unlock_irq(&tscm->lock);
+
+				wake_up(&tscm->hwdep_wait);
 			}
 		}
 
diff --git a/sound/firewire/tascam/tascam-hwdep.c b/sound/firewire/tascam/tascam-hwdep.c
index 8f34cede2e9f..0414abf5daa8 100644
--- a/sound/firewire/tascam/tascam-hwdep.c
+++ b/sound/firewire/tascam/tascam-hwdep.c
@@ -35,6 +35,65 @@ static long tscm_hwdep_read_locked(struct snd_tscm *tscm, char __user *buf,
 	return count;
 }
 
+static long tscm_hwdep_read_queue(struct snd_tscm *tscm, char __user *buf,
+				  long remained, loff_t *offset)
+{
+	char __user *pos = buf;
+	unsigned int type = SNDRV_FIREWIRE_EVENT_TASCAM_CONTROL;
+	struct snd_firewire_tascam_change *entries = tscm->queue;
+	long count;
+
+	// At least, one control event can be copied.
+	if (remained < sizeof(type) + sizeof(*entries)) {
+		spin_unlock_irq(&tscm->lock);
+		return -EINVAL;
+	}
+
+	// Copy the type field later.
+	count = sizeof(type);
+	remained -= sizeof(type);
+	pos += sizeof(type);
+
+	while (true) {
+		unsigned int head_pos;
+		unsigned int tail_pos;
+		unsigned int length;
+
+		if (tscm->pull_pos == tscm->push_pos)
+			break;
+		else if (tscm->pull_pos < tscm->push_pos)
+			tail_pos = tscm->push_pos;
+		else
+			tail_pos = SND_TSCM_QUEUE_COUNT;
+		head_pos = tscm->pull_pos;
+
+		length = (tail_pos - head_pos) * sizeof(*entries);
+		if (remained < length)
+			length = rounddown(remained, sizeof(*entries));
+		if (length == 0)
+			break;
+
+		spin_unlock_irq(&tscm->lock);
+		if (copy_to_user(pos, &entries[head_pos], length))
+			return -EFAULT;
+
+		spin_lock_irq(&tscm->lock);
+
+		tscm->pull_pos = tail_pos % SND_TSCM_QUEUE_COUNT;
+
+		count += length;
+		remained -= length;
+		pos += length;
+	}
+
+	spin_unlock_irq(&tscm->lock);
+
+	if (copy_to_user(buf, &type, sizeof(type)))
+		return -EFAULT;
+
+	return count;
+}
+
 static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 		       loff_t *offset)
 {
@@ -43,7 +102,7 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 
 	spin_lock_irq(&tscm->lock);
 
-	while (!tscm->dev_lock_changed) {
+	while (!tscm->dev_lock_changed && tscm->push_pos == tscm->pull_pos) {
 		prepare_to_wait(&tscm->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
 		spin_unlock_irq(&tscm->lock);
 		schedule();
@@ -56,6 +115,8 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 	// NOTE: The acquired lock should be released in callee side.
 	if (tscm->dev_lock_changed) {
 		count = tscm_hwdep_read_locked(tscm, buf, count, offset);
+	} else if (tscm->push_pos != tscm->pull_pos) {
+		count = tscm_hwdep_read_queue(tscm, buf, count, offset);
 	} else {
 		spin_unlock_irq(&tscm->lock);
 		count = 0;
@@ -73,7 +134,7 @@ static __poll_t hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
 	poll_wait(file, &tscm->hwdep_wait, wait);
 
 	spin_lock_irq(&tscm->lock);
-	if (tscm->dev_lock_changed)
+	if (tscm->dev_lock_changed || tscm->push_pos != tscm->pull_pos)
 		events = EPOLLIN | EPOLLRDNORM;
 	else
 		events = 0;
-- 
2.19.1