1 files changed, 63 insertions, 2 deletions

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;