usb: raw-gadget: return USB_GADGET_DELAYED_STATUS from setup()

Return USB_GADGET_DELAYED_STATUS from the setup() callback for 0-length
transfers as a workaround to stop some UDC drivers (e.g. dwc3) from
automatically proceeding with the status stage.

This workaround should be removed once all UDC drivers are fixed to
always delay the status stage until a response is queued to EP0.

Signed-off-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/c56077322f0d3fc6d504092a266cb89d75701087.1693237258.git.andreyknvl@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/legacy/raw_gadget.c

@@ -25,6 +25,7 @@
 #include <linux/usb/ch9.h>
 #include <linux/usb/ch11.h>
 #include <linux/usb/gadget.h>
+#include <linux/usb/composite.h>
 
 #include <uapi/linux/usb/raw_gadget.h>
 
@@ -363,6 +364,16 @@ static int gadget_setup(struct usb_gadget *gadget,
 out_unlock:
 	spin_unlock_irqrestore(&dev->lock, flags);
 out:
+	if (ret == 0 && ctrl->wLength == 0) {
+		/*
+		 * Return USB_GADGET_DELAYED_STATUS as a workaround to stop
+		 * some UDC drivers (e.g. dwc3) from automatically proceeding
+		 * with the status stage for 0-length transfers.
+		 * Should be removed once all UDC drivers are fixed to always
+		 * delay the status stage until a response is queued to EP0.
+		 */
+		return USB_GADGET_DELAYED_STATUS;
+	}
 	return ret;
 }