windows: Correct isochronous frame calculation for full-speed devices
The WinUSB isochronous transfer implementation always assumed HighSpeed
microframes.
https://github.com/libusb/libusb/issues/747#issuecomment-649491619
References #747
References #749
diff --git a/libusb/os/windows_winusb.c b/libusb/os/windows_winusb.c
index fed7d0d..6c0db2a 100644
--- a/libusb/os/windows_winusb.c
+++ b/libusb/os/windows_winusb.c
@@ -2990,7 +2990,11 @@
// WinUSB only supports isoch transfers spanning a full USB frames. Later, we might be smarter about this
// and allocate a temporary buffer. However, this is harder than it seems as its destruction would depend on overlapped
// IO...
- iso_transfer_size_multiple = (pipe_info_ex.MaximumBytesPerInterval * 8) / interval;
+ if (transfer->dev_handle->dev->speed >= LIBUSB_SPEED_HIGH) // Microframes (125us)
+ iso_transfer_size_multiple = (pipe_info_ex.MaximumBytesPerInterval * 8) / interval;
+ else // Normal Frames (1ms)
+ iso_transfer_size_multiple = pipe_info_ex.MaximumBytesPerInterval / interval;
+
if (transfer->length % iso_transfer_size_multiple != 0) {
usbi_err(TRANSFER_CTX(transfer), "length of isoch buffer must be a multiple of the MaximumBytesPerInterval * 8 / Interval");
return LIBUSB_ERROR_INVALID_PARAM;
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 78fef60..f9d6b03 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11713
+#define LIBUSB_NANO 11714
