usb: gadget: f_uac2: allow changing terminal types through configfs

Add "c_terminal_type" and "p_terminal_type" configfs entries
in order to allow the user to change the capture and playback terminal
type codes.

These fields affect the type of audio device that Windows detects, so
being able to modify this is useful when it would be advantageous for
a gadget to be detected as something other than a generic
speaker/microphone.

The fields default to microphone for the capture type field and speaker
for the playback type field as was the case before.

Signed-off-by: James Gruber <jimmyjgruber@gmail.com>
Link: https://lore.kernel.org/r/20230914222746.155126-1-jimmyjgruber@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/configfs-usb-gadget-uac2

@@ -35,4 +35,6 @@ Description:
 		req_number		the number of pre-allocated requests
 					for both capture and playback
 		function_name		name of the interface
+		c_terminal_type		code of the capture terminal type
+		p_terminal_type		code of the playback terminal type
 		=====================	=======================================

Documentation/usb/gadget-testing.rst

@@ -755,6 +755,8 @@ The uac2 function provides these attributes in its function directory:
 	req_number       the number of pre-allocated request for both capture
 	                 and playback
 	function_name    name of the interface
+	c_terminal_type  code of the capture terminal type
+	p_terminal_type  code of the playback terminal type
 	================ ====================================================
 
 The attributes have sane default values.

drivers/usb/gadget/function/f_uac2.c

@@ -212,7 +212,7 @@ static struct uac2_input_terminal_descriptor io_in_it_desc = {
 
 	.bDescriptorSubtype = UAC_INPUT_TERMINAL,
 	/* .bTerminalID = DYNAMIC */
-	.wTerminalType = cpu_to_le16(UAC_INPUT_TERMINAL_MICROPHONE),
+	/* .wTerminalType = DYNAMIC */
 	.bAssocTerminal = 0,
 	/* .bCSourceID = DYNAMIC */
 	.iChannelNames = 0,
@@ -240,7 +240,7 @@ static struct uac2_output_terminal_descriptor io_out_ot_desc = {
 
 	.bDescriptorSubtype = UAC_OUTPUT_TERMINAL,
 	/* .bTerminalID = DYNAMIC */
-	.wTerminalType = cpu_to_le16(UAC_OUTPUT_TERMINAL_SPEAKER),
+	/* .wTerminalType = DYNAMIC */
 	.bAssocTerminal = 0,
 	/* .bSourceID = DYNAMIC */
 	/* .bCSourceID = DYNAMIC */
@@ -977,6 +977,9 @@ static void setup_descriptor(struct f_uac2_opts *opts)
 		iad_desc.bInterfaceCount++;
 	}
 
+	io_in_it_desc.wTerminalType = cpu_to_le16(opts->c_terminal_type);
+	io_out_ot_desc.wTerminalType = cpu_to_le16(opts->p_terminal_type);
+
 	setup_headers(opts, fs_audio_desc, USB_SPEED_FULL);
 	setup_headers(opts, hs_audio_desc, USB_SPEED_HIGH);
 	setup_headers(opts, ss_audio_desc, USB_SPEED_SUPER);
@@ -2095,6 +2098,9 @@ UAC2_ATTRIBUTE(s16, c_volume_res);
 UAC2_ATTRIBUTE(u32, fb_max);
 UAC2_ATTRIBUTE_STRING(function_name);
 
+UAC2_ATTRIBUTE(s16, p_terminal_type);
+UAC2_ATTRIBUTE(s16, c_terminal_type);
+
 static struct configfs_attribute *f_uac2_attrs[] = {
 	&f_uac2_opts_attr_p_chmask,
 	&f_uac2_opts_attr_p_srate,
@@ -2122,6 +2128,9 @@ static struct configfs_attribute *f_uac2_attrs[] = {
 
 	&f_uac2_opts_attr_function_name,
 
+	&f_uac2_opts_attr_p_terminal_type,
+	&f_uac2_opts_attr_c_terminal_type,
+
 	NULL,
 };
 
@@ -2180,6 +2189,9 @@ static struct usb_function_instance *afunc_alloc_inst(void)
 
 	snprintf(opts->function_name, sizeof(opts->function_name), "Source/Sink");
 
+	opts->p_terminal_type = UAC2_DEF_P_TERM_TYPE;
+	opts->c_terminal_type = UAC2_DEF_C_TERM_TYPE;
+
 	return &opts->func_inst;
 }
 

drivers/usb/gadget/function/u_uac2.h

@@ -35,6 +35,11 @@
 #define UAC2_DEF_REQ_NUM 2
 #define UAC2_DEF_INT_REQ_NUM	10
 
+#define UAC2_DEF_P_TERM_TYPE 0x301
+	/* UAC_OUTPUT_TERMINAL_SPEAKER */
+#define UAC2_DEF_C_TERM_TYPE 0x201
+	/* UAC_INPUT_TERMINAL_MICROPHONE*/
+
 struct f_uac2_opts {
 	struct usb_function_instance	func_inst;
 	int				p_chmask;
@@ -65,6 +70,9 @@ struct f_uac2_opts {
 
 	char			function_name[32];
 
+	s16				p_terminal_type;
+	s16				c_terminal_type;
+
 	struct mutex			lock;
 	int				refcnt;
 };