1 files changed, 70 insertions, 0 deletions

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 63868d36..b2d3a980 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -110,6 +110,71 @@ static DEFINE_MUTEX(register_mutex);
 static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
 static struct usb_driver usb_audio_driver;
 
+struct snd_usb_substream *find_snd_usb_substream(unsigned int card_num,
+	unsigned int pcm_idx, unsigned int direction, struct snd_usb_audio
+	**uchip, void (*disconnect_cb)(struct snd_usb_audio *chip))
+{
+	int idx;
+	struct snd_usb_stream *as;
+	struct snd_usb_substream *subs = NULL;
+	struct snd_usb_audio *chip = NULL;
+
+	mutex_lock(&register_mutex);
+	/*
+	 * legacy audio snd card number assignment is dynamic. Hence
+	 * search using chip->card->number
+	 */
+	for (idx = 0; idx < SNDRV_CARDS; idx++) {
+		if (!usb_chip[idx])
+			continue;
+		if (usb_chip[idx]->card->number == card_num) {
+			chip = usb_chip[idx];
+			break;
+		}
+	}
+
+	if (!chip || chip->shutdown) {
+		pr_debug("%s: instance of usb crad # %d does not exist\n",
+			__func__, card_num);
+		goto err;
+	}
+
+	if (pcm_idx >= chip->pcm_devs) {
+		pr_err("%s: invalid pcm dev number %u > %d\n", __func__,
+			pcm_idx, chip->pcm_devs);
+		goto err;
+	}
+
+	if (direction > SNDRV_PCM_STREAM_CAPTURE) {
+		pr_err("%s: invalid direction %u\n", __func__, direction);
+		goto err;
+	}
+
+	list_for_each_entry(as, &chip->pcm_list, list) {
+		if (as->pcm_index == pcm_idx) {
+			subs = &as->substream[direction];
+			if (subs->interface < 0 && !subs->data_endpoint &&
+				!subs->sync_endpoint) {
+				pr_debug("%s: stream disconnected, bail out\n",
+					__func__);
+				subs = NULL;
+				goto err;
+			}
+			goto done;
+		}
+	}
+
+done:
+	chip->card_num = card_num;
+	chip->disconnect_cb = disconnect_cb;
+err:
+	*uchip = chip;
+	if (!subs)
+		pr_debug("%s: substream instance not found\n", __func__);
+	mutex_unlock(&register_mutex);
+	return subs;
+}
+
 /*
  * disconnect streams
  * called from snd_usb_audio_disconnect()
@@ -324,6 +389,7 @@ static int snd_usb_audio_free(struct snd_usb_audio *chip)
 	list_for_each_safe(p, n, &chip->ep_list)
 		snd_usb_endpoint_free(p);
 
+	mutex_destroy(&chip->dev_lock);
 	mutex_destroy(&chip->mutex);
 	kfree(chip);
 	return 0;
@@ -390,6 +456,7 @@ static int snd_usb_audio_create(struct usb_interface *intf,
 
 	mutex_init(&chip->mutex);
 	init_rwsem(&chip->shutdown_rwsem);
+	mutex_init(&chip->dev_lock);
 	chip->index = idx;
 	chip->dev = dev;
 	chip->card = card;
@@ -614,6 +681,9 @@ static void snd_usb_audio_disconnect(struct usb_device *dev,
 	chip->shutdown = 1;
 	up_write(&chip->shutdown_rwsem);
 
+	if (chip->disconnect_cb)
+		chip->disconnect_cb(chip);
+
 	mutex_lock(&register_mutex);
 	if (!was_shutdown) {
 		struct snd_usb_endpoint *ep;