usb: gadget: f_uac2: Add missing companion descriptor for feedback EP

The f_uac2 function fails to enumerate when connected in SuperSpeed
due to the feedback endpoint missing the companion descriptor.
Add a new ss_epin_fback_desc_comp descriptor and append it behind the
ss_epin_fback_desc both in the static definition of the ss_audio_desc
structure as well as its dynamic construction in setup_headers().

Fixes: 24f779da ("usb: gadget: f_uac2/u_audio: add feedback endpoint support")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Link: https://lore.kernel.org/r/20210909174811.12534-2-jackp@codeaurora.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/f_uac2.c

@@ -406,6 +406,14 @@ static struct usb_endpoint_descriptor ss_epin_fback_desc = {
 	.bInterval = 4,
 };
 
+static struct usb_ss_ep_comp_descriptor ss_epin_fback_desc_comp = {
+	.bLength		= sizeof(ss_epin_fback_desc_comp),
+	.bDescriptorType	= USB_DT_SS_ENDPOINT_COMP,
+	.bMaxBurst		= 0,
+	.bmAttributes		= 0,
+	.wBytesPerInterval	= cpu_to_le16(4),
+};
+
 
 /* Audio Streaming IN Interface - Alt0 */
 static struct usb_interface_descriptor std_as_in_if0_desc = {
@@ -597,6 +605,7 @@ static struct usb_descriptor_header *ss_audio_desc[] = {
 	(struct usb_descriptor_header *)&ss_epout_desc_comp,
 	(struct usb_descriptor_header *)&as_iso_out_desc,
 	(struct usb_descriptor_header *)&ss_epin_fback_desc,
+	(struct usb_descriptor_header *)&ss_epin_fback_desc_comp,
 
 	(struct usb_descriptor_header *)&std_as_in_if0_desc,
 	(struct usb_descriptor_header *)&std_as_in_if1_desc,
@@ -705,6 +714,7 @@ static void setup_headers(struct f_uac2_opts *opts,
 {
 	struct usb_ss_ep_comp_descriptor *epout_desc_comp = NULL;
 	struct usb_ss_ep_comp_descriptor *epin_desc_comp = NULL;
+	struct usb_ss_ep_comp_descriptor *epin_fback_desc_comp = NULL;
 	struct usb_endpoint_descriptor *epout_desc;
 	struct usb_endpoint_descriptor *epin_desc;
 	struct usb_endpoint_descriptor *epin_fback_desc;
@@ -730,6 +740,7 @@ static void setup_headers(struct f_uac2_opts *opts,
 		epout_desc_comp = &ss_epout_desc_comp;
 		epin_desc_comp = &ss_epin_desc_comp;
 		epin_fback_desc = &ss_epin_fback_desc;
+		epin_fback_desc_comp = &ss_epin_fback_desc_comp;
 		ep_int_desc = &ss_ep_int_desc;
 	}
 
@@ -773,8 +784,11 @@ static void setup_headers(struct f_uac2_opts *opts,
 
 		headers[i++] = USBDHDR(&as_iso_out_desc);
 
-		if (EPOUT_FBACK_IN_EN(opts))
+		if (EPOUT_FBACK_IN_EN(opts)) {
 			headers[i++] = USBDHDR(epin_fback_desc);
+			if (epin_fback_desc_comp)
+				headers[i++] = USBDHDR(epin_fback_desc_comp);
+		}
 	}
 
 	if (EPIN_EN(opts)) {