Samples: fix a "value is always 0" Clang warning in xusb.c

* Remove the use of os_fd[i].recipient and alter comments with
  regards to Windows Extended Props test limitations with WinUSB

diff --git a/examples/xusb.c b/examples/xusb.c
index b94aa1f7fe9e7078e2371c3b3d302a62acad32be..f1682ad3fa3eba1e964af98bfd885f678bbef572 100644 (file)
--- a/examples/xusb.c
+++ b/examples/xusb.c
@@ -541,12 +541,7 @@ void read_ms_winsub_feature_descriptors(libusb_device_handle *handle, uint8_t bR
                uint16_t header_size;
        } os_fd[2] = {
                {"Extended Compat ID", LIBUSB_RECIPIENT_DEVICE, 0x0004, 0x10},
-               {"Extended Properties", LIBUSB_RECIPIENT_DEVICE, 0x0005, 0x0A}
-               // NB: LIBUSB_RECIPIENT_INTERFACE should be used for the Extended Properties.
-               // However, for Interface requests, the WinUSB DLL forces the low byte of wIndex
-               // to the interface number, regardless of what you set it to, so we have to
-               // fallback to Device and hope the firmware answers both equally.
-               // See http://www.lvr.com/forum/index.php?topic=331
+               {"Extended Properties", LIBUSB_RECIPIENT_INTERFACE, 0x0005, 0x0A}
        };
 
        if (iface_number < 0) return;
@@ -555,7 +550,13 @@ void read_ms_winsub_feature_descriptors(libusb_device_handle *handle, uint8_t bR
                printf("\nReading %s OS Feature Descriptor (wIndex = 0x%04d):\n", os_fd[i].desc, os_fd[i].index);
 
                // Read the header part
-               r = libusb_control_transfer(handle, (uint8_t)(LIBUSB_ENDPOINT_IN|LIBUSB_REQUEST_TYPE_VENDOR|os_fd[i].recipient),
+               r = libusb_control_transfer(handle, (uint8_t)(LIBUSB_ENDPOINT_IN|LIBUSB_REQUEST_TYPE_VENDOR|LIBUSB_RECIPIENT_DEVICE),
+                       // NB: We should use os_fd[i].recipient instead of LIBUSB_RECIPIENT_DEVICE above, as 
+                       // LIBUSB_RECIPIENT_INTERFACE should be used for the Extended Properties.
+                       // However, for Interface requests, the WinUSB DLL forces the low byte of wIndex
+                       // to the interface number, regardless of what you set it to, so we have to
+                       // fallback to Device and hope the firmware answers both equally.
+                       // See http://www.lvr.com/forum/index.php?topic=331
                        bRequest, (uint16_t)(((iface_number)<< 8)|0x00), os_fd[i].index, os_desc, os_fd[i].header_size, 1000);
                if (r < os_fd[i].header_size) {
                        perr("   Failed: %s", (r<0)?libusb_error_name((enum libusb_error)r):"header size is too small");