3 files changed, 21 insertions, 4 deletions

diff --git a/sys/dev/usb/usb_device.c b/sys/dev/usb/usb_device.c
index 3499516c91e6c..cc679611a832b 100644
--- a/sys/dev/usb/usb_device.c
+++ b/sys/dev/usb/usb_device.c
@@ -2,7 +2,7 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
  *
- * Copyright (c) 2008 Hans Petter Selasky. All rights reserved.
+ * Copyright (c) 2008-2020 Hans Petter Selasky. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -905,6 +905,10 @@ usb_config_parse(struct usb_device *udev, uint8_t iface_index, uint8_t cmd)
 			/* update current number of endpoints */
 			ep_curr = ep_max;
 		}
+		/* update number of alternate settings, if any */
+		if (iface_index == USB_IFACE_INDEX_ANY)
+			iface->num_altsetting = ips.iface_index_alt + 1;
+
 		/* check for init */
 		if (do_init) {
 			/* setup the USB interface structure */
diff --git a/sys/dev/usb/usb_request.c b/sys/dev/usb/usb_request.c
index 36c6a28124c59..a1781f3589a44 100644
--- a/sys/dev/usb/usb_request.c
+++ b/sys/dev/usb/usb_request.c
@@ -4,7 +4,7 @@
  *
  * Copyright (c) 1998 The NetBSD Foundation, Inc. All rights reserved.
  * Copyright (c) 1998 Lennart Augustsson. All rights reserved.
- * Copyright (c) 2008 Hans Petter Selasky. All rights reserved.
+ * Copyright (c) 2008-2020 Hans Petter Selasky. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -1436,6 +1436,7 @@ usbd_req_set_alt_interface_no(struct usb_device *udev, struct mtx *mtx,
 {
 	struct usb_interface *iface = usbd_get_iface(udev, iface_index);
 	struct usb_device_request req;
+	usb_error_t err;
 
 	if ((iface == NULL) || (iface->idesc == NULL))
 		return (USB_ERR_INVAL);
@@ -1447,7 +1448,17 @@ usbd_req_set_alt_interface_no(struct usb_device *udev, struct mtx *mtx,
 	req.wIndex[0] = iface->idesc->bInterfaceNumber;
 	req.wIndex[1] = 0;
 	USETW(req.wLength, 0);
-	return (usbd_do_request(udev, mtx, &req, 0));
+	err = usbd_do_request(udev, mtx, &req, 0);
+	if (err == USB_ERR_STALLED && iface->num_altsetting == 1) {
+		/*
+		 * The USB specification chapter 9.4.10 says that USB
+		 * devices having only one alternate setting are
+		 * allowed to STALL this request. Ignore this failure.
+		 */
+		err = 0;
+		DPRINTF("Setting default alternate number failed. (ignored)\n");
+	}
+	return (err);
 }
 
 /*------------------------------------------------------------------------*
diff --git a/sys/dev/usb/usbdi.h b/sys/dev/usb/usbdi.h
index a8ba5408f5c4d..1b3b4af5f7170 100644
--- a/sys/dev/usb/usbdi.h
+++ b/sys/dev/usb/usbdi.h
@@ -174,6 +174,9 @@ struct usb_endpoint {
 struct usb_interface {
 	struct usb_interface_descriptor *idesc;
 	device_t subdev;
+	/* Total number of alternate settings, from 1 to 256 */
+	uint16_t num_altsetting;
+	/* Current alternate interface index, from 0 to 255 */
 	uint8_t	alt_index;
 	uint8_t	parent_iface_index;
 
@@ -183,7 +186,6 @@ struct usb_interface {
 	struct usb_device *linux_udev;
 	void   *bsd_priv_sc;		/* device specific information */
 	char   *pnpinfo;		/* additional PnP-info for this interface */
-	uint8_t	num_altsetting;		/* number of alternate settings */
 	uint8_t	bsd_iface_index;
 };