usb: gadget: f_uac2: convert to new function interface with backward compatibility

Converting uac2 to the new function interface requires converting
the USB uac2's function code and its users.

This patch converts the f_uac2.c to the new function interface.

The file is now compiled into a separate usb_f_uac2.ko module.

The old function interface is provided by means of a preprocessor
conditional directives. After all users are converted, the old interface
can be removed.
Tested-by: Sebastian Reimers <sebastian.reimers@googlemail.com>
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/Kconfig

@@ -181,6 +181,9 @@ config USB_F_MASS_STORAGE
 config USB_F_FS
 	tristate
 
+config USB_F_UAC2
+	tristate
+
 choice
 	tristate "USB Gadget Drivers"
 	default USB_ETH

drivers/usb/gadget/function/Makefile

@@ -32,3 +32,5 @@ usb_f_mass_storage-y		:= f_mass_storage.o storage_common.o
 obj-$(CONFIG_USB_F_MASS_STORAGE)+= usb_f_mass_storage.o
 usb_f_fs-y			:= f_fs.o
 obj-$(CONFIG_USB_F_FS)		+= usb_f_fs.o
+usb_f_uac2-y			:= f_uac2.o
+obj-$(CONFIG_USB_F_UAC2)	+= usb_f_uac2.o

drivers/usb/gadget/function/u_uac2.h

+/*
+ * u_uac2.h
+ *
+ * Utility definitions for UAC2 function
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ *		http://www.samsung.com
+ *
+ * Author: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef U_UAC2_H
+#define U_UAC2_H
+
+#include <linux/usb/composite.h>
+
+struct f_uac2_opts {
+	struct usb_function_instance	func_inst;
+	int				p_chmask;
+	int				p_srate;
+	int				p_ssize;
+	int				c_chmask;
+	int				c_srate;
+	int				c_ssize;
+	bool				bound;
+};
+
+#endif

drivers/usb/gadget/legacy/audio.c

@@ -45,6 +45,7 @@ static struct usb_gadget_strings *audio_strings[] = {
 #include "u_uac1.c"
 #include "f_uac1.c"
 #else
+#define USB_FUAC2_INCLUDED
 #include "f_uac2.c"
 #endif