ALSA: dice: implement hwdep device

Implement the hwdep locking and notification mechanisms.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

sound/firewire/dice.c

@@ -5,6 +5,7 @@
  * Licensed under the terms of the GNU General Public License, version 2.
  */
 
+#include <linux/compat.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/firewire.h>
@@ -13,8 +14,11 @@
 #include <linux/mod_devicetable.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/wait.h>
 #include <sound/control.h>
 #include <sound/core.h>
+#include <sound/firewire.h>
 #include <sound/hwdep.h>
 #include <sound/initval.h>
 #include <sound/pcm.h>
@@ -233,13 +237,18 @@
 struct dice {
 	struct snd_card *card;
 	struct fw_unit *unit;
+	spinlock_t lock;
 	struct mutex mutex;
 	unsigned int global_offset;
 	unsigned int rx_offset;
 	struct fw_address_handler notification_handler;
 	int owner_generation;
+	int dev_lock_count; /* > 0 driver, < 0 userspace */
+	bool dev_lock_changed;
 	bool global_enabled;
 	bool stream_running;
+	wait_queue_head_t hwdep_wait;
+	u32 notification_bits;
 	struct snd_pcm_substream *pcm;
 	struct fw_iso_resources resources;
 	struct amdtp_out_stream stream;
@@ -259,6 +268,47 @@ static const unsigned int dice_rates[] = {
 	[6] = 192000,
 };
 
+static void dice_lock_changed(struct dice *dice)
+{
+	dice->dev_lock_changed = true;
+	wake_up(&dice->hwdep_wait);
+}
+
+static int dice_try_lock(struct dice *dice)
+{
+	int err;
+
+	spin_lock_irq(&dice->lock);
+
+	if (dice->dev_lock_count < 0) {
+		err = -EBUSY;
+		goto out;
+	}
+
+	if (dice->dev_lock_count++ == 0)
+		dice_lock_changed(dice);
+	err = 0;
+
+out:
+	spin_unlock_irq(&dice->lock);
+
+	return err;
+}
+
+static void dice_unlock(struct dice *dice)
+{
+	spin_lock_irq(&dice->lock);
+
+	if (WARN_ON(dice->dev_lock_count <= 0))
+		goto out;
+
+	if (--dice->dev_lock_count == 0)
+		dice_lock_changed(dice);
+
+out:
+	spin_unlock_irq(&dice->lock);
+}
+
 static inline u64 global_address(struct dice *dice, unsigned int offset)
 {
 	return DICE_PRIVATE_SPACE + dice->global_offset + offset;
@@ -496,6 +546,7 @@ static void dice_notification(struct fw_card *card, struct fw_request *request,
 			      void *data, size_t length, void *callback_data)
 {
 	struct dice *dice = callback_data;
+	unsigned long flags;
 
 	if (tcode != TCODE_WRITE_QUADLET_REQUEST) {
 		fw_send_response(card, request, RCODE_TYPE_ERROR);
@@ -505,9 +556,11 @@ static void dice_notification(struct fw_card *card, struct fw_request *request,
 		fw_send_response(card, request, RCODE_ADDRESS_ERROR);
 		return;
 	}
-	dev_dbg(&dice->unit->device,
-		"notification: %08x\n", be32_to_cpup(data));
+	spin_lock_irqsave(&dice->lock, flags);
+	dice->notification_bits |= be32_to_cpup(data);
+	spin_unlock_irqrestore(&dice->lock, flags);
 	fw_send_response(card, request, RCODE_COMPLETE);
+	wake_up(&dice->hwdep_wait);
 }
 
 static int dice_open(struct snd_pcm_substream *substream)
@@ -531,26 +584,32 @@ static int dice_open(struct snd_pcm_substream *substream)
 	unsigned int rate;
 	int err;
 
+	err = dice_try_lock(dice);
+	if (err < 0)
+		goto error;
+
 	err = snd_fw_transaction(dice->unit, TCODE_READ_QUADLET_REQUEST,
 				 global_address(dice, GLOBAL_CLOCK_SELECT),
 				 &clock_sel, 4);
 	if (err < 0)
-		return err;
+		goto err_lock;
 	rate = (be32_to_cpu(clock_sel) & CLOCK_RATE_MASK) >> CLOCK_RATE_SHIFT;
-	if (rate >= ARRAY_SIZE(dice_rates))
-		return -ENXIO;
+	if (rate >= ARRAY_SIZE(dice_rates)) {
+		err = -ENXIO;
+		goto err_lock;
+	}
 	rate = dice_rates[rate];
 
 	err = snd_fw_transaction(dice->unit, TCODE_READ_QUADLET_REQUEST,
 				 rx_address(dice, RX_NUMBER_AUDIO),
 				 &number_audio, 4);
 	if (err < 0)
-		return err;
+		goto err_lock;
 	err = snd_fw_transaction(dice->unit, TCODE_READ_QUADLET_REQUEST,
 				 rx_address(dice, RX_NUMBER_MIDI),
 				 &number_midi, 4);
 	if (err < 0)
-		return err;
+		goto err_lock;
 
 	runtime->hw = hardware;
 
@@ -568,17 +627,26 @@ static int dice_open(struct snd_pcm_substream *substream)
 					   SNDRV_PCM_HW_PARAM_PERIOD_TIME,
 					   5000, 8192000);
 	if (err < 0)
-		return err;
+		goto err_lock;
 
 	err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
 	if (err < 0)
-		return err;
+		goto err_lock;
 
 	return 0;
+
+err_lock:
+	dice_unlock(dice);
+error:
+	return err;
 }
 
 static int dice_close(struct snd_pcm_substream *substream)
 {
+	struct dice *dice = substream->private_data;
+
+	dice_unlock(dice);
+
 	return 0;
 }
 
@@ -783,45 +851,156 @@ static int dice_create_pcm(struct dice *dice)
 	return 0;
 }
 
-// TODO: implement these
-
 static long dice_hwdep_read(struct snd_hwdep *hwdep, char __user *buf,
 			    long count, loff_t *offset)
 {
-	return -EIO;
+	struct dice *dice = hwdep->private_data;
+	DEFINE_WAIT(wait);
+	union snd_firewire_event event;
+
+	spin_lock_irq(&dice->lock);
+
+	while (!dice->dev_lock_changed && dice->notification_bits == 0) {
+		prepare_to_wait(&dice->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
+		spin_unlock_irq(&dice->lock);
+		schedule();
+		finish_wait(&dice->hwdep_wait, &wait);
+		if (signal_pending(current))
+			return -ERESTARTSYS;
+		spin_lock_irq(&dice->lock);
+	}
+
+	memset(&event, 0, sizeof(event));
+	if (dice->dev_lock_changed) {
+		event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
+		event.lock_status.status = dice->dev_lock_count > 0;
+		dice->dev_lock_changed = false;
+
+		count = min(count, (long)sizeof(event.lock_status));
+	} else {
+		event.dice_notification.type = SNDRV_FIREWIRE_EVENT_DICE_NOTIFICATION;
+		event.dice_notification.notification = dice->notification_bits;
+		dice->notification_bits = 0;
+
+		count = min(count, (long)sizeof(event.dice_notification));
+	}
+
+	spin_unlock_irq(&dice->lock);
+
+	if (copy_to_user(buf, &event, count))
+		return -EFAULT;
+
+	return count;
 }
 
-static int dice_hwdep_open(struct snd_hwdep *hwdep, struct file *file)
+static unsigned int dice_hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
+				    poll_table *wait)
 {
-	return -EIO;
+	struct dice *dice = hwdep->private_data;
+	unsigned int events;
+
+	poll_wait(file, &dice->hwdep_wait, wait);
+
+	spin_lock_irq(&dice->lock);
+	if (dice->dev_lock_changed || dice->notification_bits != 0)
+		events = POLLIN | POLLRDNORM;
+	else
+		events = 0;
+	spin_unlock_irq(&dice->lock);
+
+	return events;
 }
 
-static int dice_hwdep_release(struct snd_hwdep *hwdep, struct file *file)
+static int dice_hwdep_get_info(struct dice *dice, void __user *arg)
 {
+	struct fw_device *dev = fw_parent_device(dice->unit);
+	struct snd_firewire_get_info info;
+
+	memset(&info, 0, sizeof(info));
+	info.type = SNDRV_FIREWIRE_TYPE_DICE;
+	info.card = dev->card->index;
+	*(__be32 *)&info.guid[0] = cpu_to_be32(dev->config_rom[3]);
+	*(__be32 *)&info.guid[4] = cpu_to_be32(dev->config_rom[4]);
+	strlcpy(info.device_name, dev_name(&dev->device),
+		sizeof(info.device_name));
+
+	if (copy_to_user(arg, &info, sizeof(info)))
+		return -EFAULT;
+
 	return 0;
 }
 
-static unsigned int dice_hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
-				    poll_table *wait)
+static int dice_hwdep_lock(struct dice *dice)
+{
+	int err;
+
+	spin_lock_irq(&dice->lock);
+
+	if (dice->dev_lock_count == 0) {
+		dice->dev_lock_count = -1;
+		err = 0;
+	} else {
+		err = -EBUSY;
+	}
+
+	spin_unlock_irq(&dice->lock);
+
+	return err;
+}
+
+static int dice_hwdep_unlock(struct dice *dice)
 {
-	return POLLERR | POLLHUP;
+	int err;
+
+	spin_lock_irq(&dice->lock);
+
+	if (dice->dev_lock_count == -1) {
+		dice->dev_lock_count = 0;
+		err = 0;
+	} else {
+		err = -EBADFD;
+	}
+
+	spin_unlock_irq(&dice->lock);
+
+	return err;
 }
 
 static int dice_hwdep_ioctl(struct snd_hwdep *hwdep, struct file *file,
 			    unsigned int cmd, unsigned long arg)
 {
-	return -EIO;
+	struct dice *dice = hwdep->private_data;
+
+	switch (cmd) {
+	case SNDRV_FIREWIRE_IOCTL_GET_INFO:
+		return dice_hwdep_get_info(dice, (void __user *)arg);
+	case SNDRV_FIREWIRE_IOCTL_LOCK:
+		return dice_hwdep_lock(dice);
+	case SNDRV_FIREWIRE_IOCTL_UNLOCK:
+		return dice_hwdep_unlock(dice);
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static int dice_hwdep_compat_ioctl(struct snd_hwdep *hwdep, struct file *file,
+				   unsigned int cmd, unsigned long arg)
+{
+	return dice_hwdep_ioctl(hwdep, file, cmd,
+				(unsigned long)compat_ptr(arg));
 }
+#else
+#define dice_hwdep_compat_ioctl NULL
+#endif
 
 static int dice_create_hwdep(struct dice *dice)
 {
 	static const struct snd_hwdep_ops ops = {
 		.read         = dice_hwdep_read,
-		.open         = dice_hwdep_open,
-		.release      = dice_hwdep_release,
 		.poll         = dice_hwdep_poll,
 		.ioctl        = dice_hwdep_ioctl,
-		.ioctl_compat = dice_hwdep_ioctl,
+		.ioctl_compat = dice_hwdep_compat_ioctl,
 	};
 	struct snd_hwdep *hwdep;
 	int err;
@@ -922,8 +1101,10 @@ static int dice_probe(struct fw_unit *unit, const struct ieee1394_device_id *id)
 
 	dice = card->private_data;
 	dice->card = card;
+	spin_lock_init(&dice->lock);
 	mutex_init(&dice->mutex);
 	dice->unit = unit;
+	init_waitqueue_head(&dice->hwdep_wait);
 
 	err = dice_init_offsets(dice);
 	if (err < 0)