ALSA: firewire-motu: notify event for parameter change in register DSP model

This commit copies queued event for change of register DSP into
userspace when application operates ALSA hwdep character device.
The notification occurs only when packet streaming is running.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20211015080826.34847-12-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/uapi/sound/firewire.h

@@ -13,6 +13,7 @@
 #define SNDRV_FIREWIRE_EVENT_DIGI00X_MESSAGE	0x746e736c
 #define SNDRV_FIREWIRE_EVENT_MOTU_NOTIFICATION	0x64776479
 #define SNDRV_FIREWIRE_EVENT_TASCAM_CONTROL	0x7473636d
+#define SNDRV_FIREWIRE_EVENT_MOTU_REGISTER_DSP_CHANGE	0x4d545244
 
 struct snd_firewire_event_common {
 	unsigned int type; /* SNDRV_FIREWIRE_EVENT_xxx */
@@ -65,6 +66,12 @@ struct snd_firewire_event_tascam_control {
 	struct snd_firewire_tascam_change changes[0];
 };
 
+struct snd_firewire_event_motu_register_dsp_change {
+	unsigned int type;
+	__u32 count;		// The number of changes.
+	__u32 changes[];	// Encoded event for change of register DSP.
+};
+
 union snd_firewire_event {
 	struct snd_firewire_event_common            common;
 	struct snd_firewire_event_lock_status       lock_status;
@@ -73,6 +80,7 @@ union snd_firewire_event {
 	struct snd_firewire_event_digi00x_message   digi00x_message;
 	struct snd_firewire_event_tascam_control    tascam_control;
 	struct snd_firewire_event_motu_notification motu_notification;
+	struct snd_firewire_event_motu_register_dsp_change motu_register_dsp_change;
 };
 
 

sound/firewire/motu/motu-hwdep.c

@@ -25,7 +25,8 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 
 	spin_lock_irq(&motu->lock);
 
-	while (!motu->dev_lock_changed && motu->msg == 0) {
+	while (!motu->dev_lock_changed && motu->msg == 0 &&
+			snd_motu_register_dsp_message_parser_count_event(motu) == 0) {
 		prepare_to_wait(&motu->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
 		spin_unlock_irq(&motu->lock);
 		schedule();
@@ -40,21 +41,47 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
 		event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
 		event.lock_status.status = (motu->dev_lock_count > 0);
 		motu->dev_lock_changed = false;
+		spin_unlock_irq(&motu->lock);
 
-		count = min_t(long, count, sizeof(event.lock_status));
-	} else {
+		count = min_t(long, count, sizeof(event));
+		if (copy_to_user(buf, &event, count))
+			return -EFAULT;
+	} else if (motu->msg > 0) {
 		event.motu_notification.type = SNDRV_FIREWIRE_EVENT_MOTU_NOTIFICATION;
 		event.motu_notification.message = motu->msg;
 		motu->msg = 0;
+		spin_unlock_irq(&motu->lock);
 
-		count = min_t(long, count, sizeof(event.motu_notification));
+		count = min_t(long, count, sizeof(event));
+		if (copy_to_user(buf, &event, count))
+			return -EFAULT;
+	} else if (snd_motu_register_dsp_message_parser_count_event(motu) > 0) {
+		size_t consumed = 0;
+		u32 __user *ptr;
+		u32 ev;
+
+		spin_unlock_irq(&motu->lock);
+
+		// Header is filled later.
+		consumed += sizeof(event.motu_register_dsp_change);
+
+		while (consumed < count &&
+		       snd_motu_register_dsp_message_parser_copy_event(motu, &ev)) {
+			ptr = (u32 __user *)(buf + consumed);
+			if (put_user(ev, ptr))
+				return -EFAULT;
+			consumed += sizeof(ev);
+		}
+
+		event.motu_register_dsp_change.type = SNDRV_FIREWIRE_EVENT_MOTU_REGISTER_DSP_CHANGE;
+		event.motu_register_dsp_change.count =
+			(consumed - sizeof(event.motu_register_dsp_change)) / 4;
+		if (copy_to_user(buf, &event, sizeof(event.motu_register_dsp_change)))
+			return -EFAULT;
+
+		count = consumed;
 	}
 
-	spin_unlock_irq(&motu->lock);
-
-	if (copy_to_user(buf, &event, count))
-		return -EFAULT;
-
 	return count;
 }
 
@@ -67,7 +94,8 @@ static __poll_t hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
 	poll_wait(file, &motu->hwdep_wait, wait);
 
 	spin_lock_irq(&motu->lock);
-	if (motu->dev_lock_changed || motu->msg)
+	if (motu->dev_lock_changed || motu->msg ||
+	    snd_motu_register_dsp_message_parser_count_event(motu) > 0)
 		events = EPOLLIN | EPOLLRDNORM;
 	else
 		events = 0;

sound/firewire/motu/motu-register-dsp-message-parser.c

@@ -95,6 +95,7 @@ struct msg_parser {
 
 	u32 event_queue[EVENT_QUEUE_SIZE];
 	unsigned int push_pos;
+	unsigned int pull_pos;
 };
 
 int snd_motu_register_dsp_message_parser_new(struct snd_motu *motu)
@@ -122,6 +123,7 @@ int snd_motu_register_dsp_message_parser_init(struct snd_motu *motu)
 	return 0;
 }
 
+// Rough implementaion of queue without overrun check.
 static void queue_event(struct snd_motu *motu, u8 msg_type, u8 identifier0, u8 identifier1, u8 val)
 {
 	struct msg_parser *parser = motu->message_parser;
@@ -145,6 +147,7 @@ void snd_motu_register_dsp_message_parser_parse(struct snd_motu *motu, const str
 {
 	struct msg_parser *parser = motu->message_parser;
 	bool meter_pos_quirk = parser->meter_pos_quirk;
+	unsigned int pos = parser->push_pos;
 	unsigned long flags;
 	int i;
 
@@ -351,6 +354,9 @@ void snd_motu_register_dsp_message_parser_parse(struct snd_motu *motu, const str
 		}
 	}
 
+	if (pos != parser->push_pos)
+		wake_up(&motu->hwdep_wait);
+
 	spin_unlock_irqrestore(&parser->lock, flags);
 }
 
@@ -375,3 +381,36 @@ void snd_motu_register_dsp_message_parser_copy_parameter(struct snd_motu *motu,
 	memcpy(param, &parser->param, sizeof(*param));
 	spin_unlock_irqrestore(&parser->lock, flags);
 }
+
+unsigned int snd_motu_register_dsp_message_parser_count_event(struct snd_motu *motu)
+{
+	struct msg_parser *parser = motu->message_parser;
+
+	if (parser->pull_pos > parser->push_pos)
+		return EVENT_QUEUE_SIZE - parser->pull_pos + parser->push_pos;
+	else
+		return parser->push_pos - parser->pull_pos;
+}
+
+bool snd_motu_register_dsp_message_parser_copy_event(struct snd_motu *motu, u32 *event)
+{
+	struct msg_parser *parser = motu->message_parser;
+	unsigned int pos = parser->pull_pos;
+	unsigned long flags;
+
+	if (pos == parser->push_pos)
+		return false;
+
+	spin_lock_irqsave(&parser->lock, flags);
+
+	*event = parser->event_queue[pos];
+
+	++pos;
+	if (pos >= EVENT_QUEUE_SIZE)
+		pos = 0;
+	parser->pull_pos = pos;
+
+	spin_unlock_irqrestore(&parser->lock, flags);
+
+	return true;
+}

sound/firewire/motu/motu.h

@@ -283,6 +283,8 @@ void snd_motu_register_dsp_message_parser_copy_meter(struct snd_motu *motu,
 					struct snd_firewire_motu_register_dsp_meter *meter);
 void snd_motu_register_dsp_message_parser_copy_parameter(struct snd_motu *motu,
 					struct snd_firewire_motu_register_dsp_parameter *params);
+unsigned int snd_motu_register_dsp_message_parser_count_event(struct snd_motu *motu);
+bool snd_motu_register_dsp_message_parser_copy_event(struct snd_motu *motu, u32 *event);
 
 int snd_motu_command_dsp_message_parser_new(struct snd_motu *motu);
 int snd_motu_command_dsp_message_parser_init(struct snd_motu *motu, enum cip_sfc sfc);