[RFC PATCH v2 12/22] sound: usb: card: Introduce USB SND platform op callbacks

[Wesley Cheng <quic_wcheng@xxxxxxxxxxx>]

Allow for different platforms to be notified on USB SND connect/disconnect
seqeunces.  This allows for platform 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 | 28 ++++++++++++++++++++++++++++
 sound/usb/card.h | 20 ++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 26268ffb8274..803230343c16 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -117,6 +117,24 @@ 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_platform_ops *platform_ops;
+
+int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops)
+{
+	if (platform_ops)
+		return -EEXIST;
+
+	platform_ops = ops;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_usb_register_platform_ops);
+
+int snd_usb_unregister_platform_ops(void)
+{
+	platform_ops = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_usb_unregister_platform_ops);
 
 /*
  * disconnect streams
@@ -910,6 +928,10 @@ static int usb_audio_probe(struct usb_interface *intf,
 	usb_set_intfdata(intf, chip);
 	atomic_dec(&chip->active);
 	mutex_unlock(&register_mutex);
+
+	if (platform_ops->connect_cb)
+		platform_ops->connect_cb(intf, chip);
+
 	return 0;
 
  __error:
@@ -943,6 +965,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
 	if (chip == USB_AUDIO_IFACE_UNUSED)
 		return;
 
+	if (platform_ops->disconnect_cb)
+		platform_ops->disconnect_cb(intf);
+
 	card = chip->card;
 
 	mutex_lock(&register_mutex);
@@ -1087,6 +1112,9 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
 		chip->system_suspend = chip->num_suspended_intf;
 	}
 
+	if (platform_ops->suspend_cb)
+		platform_ops->suspend_cb(intf, message);
+
 	return 0;
 }
 
diff --git a/sound/usb/card.h b/sound/usb/card.h
index 40061550105a..2249c411c3a1 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -206,4 +206,24 @@ struct snd_usb_stream {
 	struct list_head list;
 };
 
+struct snd_usb_platform_ops {
+	void (*connect_cb)(struct usb_interface *intf, struct snd_usb_audio *chip);
+	void (*disconnect_cb)(struct usb_interface *intf);
+	void (*suspend_cb)(struct usb_interface *intf, pm_message_t message);
+};
+
+#if IS_ENABLED(CONFIG_SND_USB_AUDIO)
+int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);
+int snd_usb_unregister_platform_ops(void);
+#else
+int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops)
+{
+	return -EOPNOTSUPP;
+}
+
+int snd_usb_unregister_platform_ops(void)
+{
+	return -EOPNOTSUPP;
+}
+#endif /* IS_ENABLED(CONFIG_SND_USB_AUDIO) */
 #endif /* __USBAUDIO_CARD_H */