[RFC PATCH 04/14] sound: usb: card: Introduce USB SND vendor op callbacks

[Wesley Cheng <quic_wcheng@xxxxxxxxxxx>]

Allow for different vendors to be notified on USB SND connect/disconnect
seqeunces.  This allows for vendor USB SND modules to properly initialize
and populate internal structures with references to the USB SND chip
device.

Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
 sound/usb/card.c | 22 ++++++++++++++++++++++
 sound/usb/card.h |  7 +++++++
 2 files changed, 29 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 26268ffb8274..212f55a7683c 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -117,6 +117,21 @@ MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no)
 static DEFINE_MUTEX(register_mutex);
 static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
 static struct usb_driver usb_audio_driver;
+static struct snd_usb_vendor_ops *vendor_ops;
+
+int snd_usb_register_vendor_ops(struct snd_usb_vendor_ops *ops)
+{
+	vendor_ops = ops;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_usb_register_vendor_ops);
+
+int snd_usb_unregister_vendor_ops(void)
+{
+	vendor_ops = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_usb_unregister_vendor_ops);
 
 /*
  * disconnect streams
@@ -910,6 +925,10 @@ static int usb_audio_probe(struct usb_interface *intf,
 	usb_set_intfdata(intf, chip);
 	atomic_dec(&chip->active);
 	mutex_unlock(&register_mutex);
+
+	if (vendor_ops->connect_cb)
+		vendor_ops->connect_cb(intf, chip);
+
 	return 0;
 
  __error:
@@ -943,6 +962,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 	if (chip == USB_AUDIO_IFACE_UNUSED)
 		return;
 
+	if (vendor_ops->disconnect_cb)
+		vendor_ops->disconnect_cb(intf);
+
 	card = chip->card;
 
 	mutex_lock(&register_mutex);
diff --git a/sound/usb/card.h b/sound/usb/card.h
index 40061550105a..a785bb256b0d 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -206,4 +206,11 @@ struct snd_usb_stream {
 	struct list_head list;
 };
 
+struct snd_usb_vendor_ops {
+	void (*connect_cb)(struct usb_interface *intf, struct snd_usb_audio *chip);
+	void (*disconnect_cb)(struct usb_interface *intf);
+};
+
+int snd_usb_register_vendor_ops(struct snd_usb_vendor_ops *ops);
+int snd_usb_unregister_vendor_ops(void);
 #endif /* __USBAUDIO_CARD_H */