usb: dwc3: gadget: Add support for snps,reserved-endpoints property

The snps,reserved-endpoints property lists the reserved endpoints
that shouldn't be used for normal transfers. Add support for that
to the driver.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Ferry Toth <fntoth@gmail.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20250212193116.2487289-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: andy-shev

drivers/usb/dwc3/gadget.c

@@ -3403,14 +3403,53 @@ static int dwc3_gadget_init_endpoint(struct dwc3 *dwc, u8 epnum)
 	return 0;
 }
 
+static int dwc3_gadget_get_reserved_endpoints(struct dwc3 *dwc, const char *propname,
+					      u8 *eps, u8 num)
+{
+	u8 count;
+	int ret;
+
+	if (!device_property_present(dwc->dev, propname))
+		return 0;
+
+	ret = device_property_count_u8(dwc->dev, propname);
+	if (ret < 0)
+		return ret;
+	count = ret;
+
+	ret = device_property_read_u8_array(dwc->dev, propname, eps, min(num, count));
+	if (ret)
+		return ret;
+
+	return count;
+}
+
 static int dwc3_gadget_init_endpoints(struct dwc3 *dwc, u8 total)
 {
+	const char			*propname = "snps,reserved-endpoints";
 	u8				epnum;
+	u8				reserved_eps[DWC3_ENDPOINTS_NUM];
+	u8				count;
+	u8				num;
+	int				ret;
 
 	INIT_LIST_HEAD(&dwc->gadget->ep_list);
 
+	ret = dwc3_gadget_get_reserved_endpoints(dwc, propname,
+						 reserved_eps, ARRAY_SIZE(reserved_eps));
+	if (ret < 0) {
+		dev_err(dwc->dev, "failed to read %s\n", propname);
+		return ret;
+	}
+	count = ret;
+
 	for (epnum = 0; epnum < total; epnum++) {
-		int			ret;
+		for (num = 0; num < count; num++) {
+			if (epnum == reserved_eps[num])
+				break;
+		}
+		if (num < count)
+			continue;
 
 		ret = dwc3_gadget_init_endpoint(dwc, epnum);
 		if (ret)