[PATCH 5/6] ALSA: fireface: add local framework to message parser

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

This commit adds local framework to message parser. This is preparation
for future work to pass event of knob control for Fireface 400 to user
space.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
---
 sound/firewire/fireface/ff-hwdep.c       | 41 +++++++++++++++++-------
 sound/firewire/fireface/ff-transaction.c |  4 +++
 sound/firewire/fireface/ff.c             | 10 ++++++
 sound/firewire/fireface/ff.h             |  5 +++
 4 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/sound/firewire/fireface/ff-hwdep.c b/sound/firewire/fireface/ff-hwdep.c
index ea64a2a41eea..8a741b3b0436 100644
--- a/sound/firewire/fireface/ff-hwdep.c
+++ b/sound/firewire/fireface/ff-hwdep.c
@@ -15,16 +15,23 @@
 
 #include "ff.h"
 
+static bool has_msg(struct snd_ff *ff)
+{
+	if (ff->spec->protocol->has_msg)
+		return ff->spec->protocol->has_msg(ff);
+	else
+		return 0;
+}
+
 static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf,  long count,
 		       loff_t *offset)
 {
 	struct snd_ff *ff = hwdep->private_data;
 	DEFINE_WAIT(wait);
-	union snd_firewire_event event;
 
 	spin_lock_irq(&ff->lock);
 
-	while (!ff->dev_lock_changed) {
+	while (!ff->dev_lock_changed && !has_msg(ff)) {
 		prepare_to_wait(&ff->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
 		spin_unlock_irq(&ff->lock);
 		schedule();
@@ -34,17 +41,29 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf,  long count,
 		spin_lock_irq(&ff->lock);
 	}
 
-	memset(&event, 0, sizeof(event));
-	event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
-	event.lock_status.status = (ff->dev_lock_count > 0);
-	ff->dev_lock_changed = false;
+	if (ff->dev_lock_changed && count >= sizeof(struct snd_firewire_event_lock_status)) {
+		struct snd_firewire_event_lock_status ev = {
+			.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS,
+			.status = (ff->dev_lock_count > 0),
+		};
 
-	count = min_t(long, count, sizeof(event.lock_status));
+		ff->dev_lock_changed = false;
 
-	spin_unlock_irq(&ff->lock);
+		spin_unlock_irq(&ff->lock);
 
-	if (copy_to_user(buf, &event, count))
-		return -EFAULT;
+		if (copy_to_user(buf, &ev, sizeof(ev)))
+			return -EFAULT;
+		count = sizeof(ev);
+	} else if (has_msg(ff)) {
+		// NOTE: Acquired spin lock should be released before accessing to user space in the
+		// callback since the access can cause page fault.
+		count = ff->spec->protocol->copy_msg_to_user(ff, buf, count);
+		spin_unlock_irq(&ff->lock);
+	} else {
+		spin_unlock_irq(&ff->lock);
+
+		count = 0;
+	}
 
 	return count;
 }
@@ -58,7 +77,7 @@ static __poll_t hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
 	poll_wait(file, &ff->hwdep_wait, wait);
 
 	spin_lock_irq(&ff->lock);
-	if (ff->dev_lock_changed)
+	if (ff->dev_lock_changed || has_msg(ff))
 		events = EPOLLIN | EPOLLRDNORM;
 	else
 		events = 0;
diff --git a/sound/firewire/fireface/ff-transaction.c b/sound/firewire/fireface/ff-transaction.c
index 79f733d8c98b..6b89e39f4a43 100644
--- a/sound/firewire/fireface/ff-transaction.c
+++ b/sound/firewire/fireface/ff-transaction.c
@@ -132,11 +132,15 @@ static void handle_msg(struct fw_card *card, struct fw_request *request, int tco
 	struct snd_ff *ff = callback_data;
 	__le32 *buf = data;
 	u32 tstamp = fw_request_get_timestamp(request);
+	unsigned long flag;
 
 	fw_send_response(card, request, RCODE_COMPLETE);
 
 	offset -= ff->async_handler.offset;
+
+	spin_lock_irqsave(&ff->lock, flag);
 	ff->spec->protocol->handle_msg(ff, (unsigned int)offset, buf, length, tstamp);
+	spin_unlock_irqrestore(&ff->lock, flag);
 }
 
 static int allocate_own_address(struct snd_ff *ff, int i)
diff --git a/sound/firewire/fireface/ff.c b/sound/firewire/fireface/ff.c
index 7bf51d062021..448e972028d9 100644
--- a/sound/firewire/fireface/ff.c
+++ b/sound/firewire/fireface/ff.c
@@ -43,6 +43,8 @@ static void ff_card_free(struct snd_card *card)
 	snd_ff_stream_destroy_duplex(ff);
 	snd_ff_transaction_unregister(ff);
 
+	kfree(ff->msg_parser);
+
 	mutex_destroy(&ff->mutex);
 	fw_unit_put(ff->unit);
 }
@@ -94,6 +96,14 @@ static int snd_ff_probe(struct fw_unit *unit, const struct ieee1394_device_id *e
 	if (err < 0)
 		goto error;
 
+	if (ff->spec->protocol->msg_parser_size > 0) {
+		ff->msg_parser = kzalloc(ff->spec->protocol->msg_parser_size, GFP_KERNEL);
+		if (!ff->msg_parser) {
+			err = -ENOMEM;
+			goto error;
+		}
+	}
+
 	err = snd_card_register(card);
 	if (err < 0)
 		goto error;
diff --git a/sound/firewire/fireface/ff.h b/sound/firewire/fireface/ff.h
index f430ebe157b3..7e42f5778a8a 100644
--- a/sound/firewire/fireface/ff.h
+++ b/sound/firewire/fireface/ff.h
@@ -97,6 +97,8 @@ struct snd_ff {
 	wait_queue_head_t hwdep_wait;
 
 	struct amdtp_domain domain;
+
+	void *msg_parser;
 };
 
 enum snd_ff_clock_src {
@@ -110,6 +112,9 @@ enum snd_ff_clock_src {
 };
 
 struct snd_ff_protocol {
+	size_t msg_parser_size;
+	bool (*has_msg)(struct snd_ff *ff);
+	long (*copy_msg_to_user)(struct snd_ff *ff, char __user *buf, long count);
 	void (*handle_msg)(struct snd_ff *ff, unsigned int offset, const __le32 *buf,
 			   size_t length, u32 tstamp);
 	int (*fill_midi_msg)(struct snd_ff *ff,
-- 
2.37.2