--- /dev/null
+/*
+ * ff-hwdep.c - a part of driver for RME Fireface series
+ *
+ * Copyright (c) 2015-2017 Takashi Sakamoto
+ *
+ * Licensed under the terms of the GNU General Public License, version 2.
+ */
+
+/*
+ * This codes give three functionality.
+ *
+ * 1.get firewire node information
+ * 2.get notification about starting/stopping stream
+ * 3.lock/unlock stream
+ */
+
+#include "ff.h"
+
+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) {
+               prepare_to_wait(&ff->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
+               spin_unlock_irq(&ff->lock);
+               schedule();
+               finish_wait(&ff->hwdep_wait, &wait);
+               if (signal_pending(current))
+                       return -ERESTARTSYS;
+               spin_lock_irq(&ff->lock);
+       }
+
+       memset(&event, 0, sizeof(event));
+       if (ff->dev_lock_changed) {
+               event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
+               event.lock_status.status = (ff->dev_lock_count > 0);
+               ff->dev_lock_changed = false;
+
+               count = min_t(long, count, sizeof(event.lock_status));
+       }
+
+       spin_unlock_irq(&ff->lock);
+
+       if (copy_to_user(buf, &event, count))
+               return -EFAULT;
+
+       return count;
+}
+
+static unsigned int hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
+                              poll_table *wait)
+{
+       struct snd_ff *ff = hwdep->private_data;
+       unsigned int events;
+
+       poll_wait(file, &ff->hwdep_wait, wait);
+
+       spin_lock_irq(&ff->lock);
+       if (ff->dev_lock_changed)
+               events = POLLIN | POLLRDNORM;
+       else
+               events = 0;
+       spin_unlock_irq(&ff->lock);
+
+       return events;
+}
+
+static int hwdep_get_info(struct snd_ff *ff, void __user *arg)
+{
+       struct fw_device *dev = fw_parent_device(ff->unit);
+       struct snd_firewire_get_info info;
+
+       memset(&info, 0, sizeof(info));
+       info.type = SNDRV_FIREWIRE_TYPE_FIREFACE;
+       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 int hwdep_lock(struct snd_ff *ff)
+{
+       int err;
+
+       spin_lock_irq(&ff->lock);
+
+       if (ff->dev_lock_count == 0) {
+               ff->dev_lock_count = -1;
+               err = 0;
+       } else {
+               err = -EBUSY;
+       }
+
+       spin_unlock_irq(&ff->lock);
+
+       return err;
+}
+
+static int hwdep_unlock(struct snd_ff *ff)
+{
+       int err;
+
+       spin_lock_irq(&ff->lock);
+
+       if (ff->dev_lock_count == -1) {
+               ff->dev_lock_count = 0;
+               err = 0;
+       } else {
+               err = -EBADFD;
+       }
+
+       spin_unlock_irq(&ff->lock);
+
+       return err;
+}
+
+static int hwdep_release(struct snd_hwdep *hwdep, struct file *file)
+{
+       struct snd_ff *ff = hwdep->private_data;
+
+       spin_lock_irq(&ff->lock);
+       if (ff->dev_lock_count == -1)
+               ff->dev_lock_count = 0;
+       spin_unlock_irq(&ff->lock);
+
+       return 0;
+}
+
+static int hwdep_ioctl(struct snd_hwdep *hwdep, struct file *file,
+                      unsigned int cmd, unsigned long arg)
+{
+       struct snd_ff *ff = hwdep->private_data;
+
+       switch (cmd) {
+       case SNDRV_FIREWIRE_IOCTL_GET_INFO:
+               return hwdep_get_info(ff, (void __user *)arg);
+       case SNDRV_FIREWIRE_IOCTL_LOCK:
+               return hwdep_lock(ff);
+       case SNDRV_FIREWIRE_IOCTL_UNLOCK:
+               return hwdep_unlock(ff);
+       default:
+               return -ENOIOCTLCMD;
+       }
+}
+
+#ifdef CONFIG_COMPAT
+static int hwdep_compat_ioctl(struct snd_hwdep *hwdep, struct file *file,
+                             unsigned int cmd, unsigned long arg)
+{
+       return hwdep_ioctl(hwdep, file, cmd,
+                          (unsigned long)compat_ptr(arg));
+}
+#else
+#define hwdep_compat_ioctl NULL
+#endif
+
+int snd_ff_create_hwdep_devices(struct snd_ff *ff)
+{
+       static const struct snd_hwdep_ops hwdep_ops = {
+               .read           = hwdep_read,
+               .release        = hwdep_release,
+               .poll           = hwdep_poll,
+               .ioctl          = hwdep_ioctl,
+               .ioctl_compat   = hwdep_compat_ioctl,
+       };
+       struct snd_hwdep *hwdep;
+       int err;
+
+       err = snd_hwdep_new(ff->card, ff->card->driver, 0, &hwdep);
+       if (err < 0)
+               return err;
+
+       strcpy(hwdep->name, ff->card->driver);
+       hwdep->iface = SNDRV_HWDEP_IFACE_FW_FIREFACE;
+       hwdep->ops = hwdep_ops;
+       hwdep->private_data = ff;
+       hwdep->exclusive = true;
+
+       return 0;
+}
 
        enum snd_ff_clock_src src;
        int i, err;
 
-       err = pcm_init_hw_params(ff, substream);
+       err = snd_ff_stream_lock_try(ff);
        if (err < 0)
                return err;
 
+       err = pcm_init_hw_params(ff, substream);
+       if (err < 0) {
+               snd_ff_stream_lock_release(ff);
+               return err;
+       }
+
        err = ff->spec->protocol->get_clock(ff, &rate, &src);
-       if (err < 0)
+       if (err < 0) {
+               snd_ff_stream_lock_release(ff);
                return err;
+       }
 
        if (src != SND_FF_CLOCK_SRC_INTERNAL) {
                for (i = 0; i < CIP_SFC_COUNT; ++i) {
                 * The unit is configured at sampling frequency which packet
                 * streaming engine can't support.
                 */
-               if (i >= CIP_SFC_COUNT)
+               if (i >= CIP_SFC_COUNT) {
+                       snd_ff_stream_lock_release(ff);
                        return -EIO;
+               }
 
                substream->runtime->hw.rate_min = rate;
                substream->runtime->hw.rate_max = rate;
 
 static int pcm_close(struct snd_pcm_substream *substream)
 {
+       struct snd_ff *ff = substream->private_data;
+
+       snd_ff_stream_lock_release(ff);
+
        return 0;
 }
 
 
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/compat.h>
+#include <linux/sched/signal.h>
 
 #include <sound/core.h>
 #include <sound/info.h>
 #include <sound/rawmidi.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>
+#include <sound/hwdep.h>
+#include <sound/firewire.h>
 
 #include "../lib.h"
 #include "../amdtp-stream.h"
        struct amdtp_stream rx_stream;
        struct fw_iso_resources tx_resources;
        struct fw_iso_resources rx_resources;
+
+       int dev_lock_count;
+       bool dev_lock_changed;
+       wait_queue_head_t hwdep_wait;
 };
 
 enum snd_ff_clock_src {
 void snd_ff_stream_stop_duplex(struct snd_ff *ff);
 void snd_ff_stream_update_duplex(struct snd_ff *ff);
 
+void snd_ff_stream_lock_changed(struct snd_ff *ff);
+int snd_ff_stream_lock_try(struct snd_ff *ff);
+void snd_ff_stream_lock_release(struct snd_ff *ff);
+
 void snd_ff_proc_init(struct snd_ff *ff);
 
 int snd_ff_create_midi_devices(struct snd_ff *ff);
 
 int snd_ff_create_pcm_devices(struct snd_ff *ff);
 
+int snd_ff_create_hwdep_devices(struct snd_ff *ff);
+
 #endif