hwstub: fix long transfers failing because of control xfer size of libusb

libusb limits control transfer sizes to 4k, see diff for details.

Change-Id: Id2e638010274009ea641d06e9040a8b9ab9d54a9

1 files changed, 4 insertions, 0 deletions

diff --git a/utils/hwstub/include/hwstub_usb.hpp b/utils/hwstub/include/hwstub_usb.hpp
index 15a0fcaaec..579594067c 100644
--- a/utils/hwstub/include/hwstub_usb.hpp
+++ b/utils/hwstub/include/hwstub_usb.hpp
@@ -101,6 +101,10 @@ public:
     void set_timeout(std::chrono::milliseconds ms);
 
 protected:
+    /* return the maximum size of a libusb control transfer, this is a "known"
+     * limitation that is completely undocumented (sigh) and applies at least
+     * to linux and windows hosts */
+    size_t max_libusb_control_xfer_size() const;
     /* interpret libusb error: >=0 means SUCCESS, others are treated as errors,
      * LIBUSB_ERROR_NO_DEVICE is treated as DISCONNECTED */
     error interpret_libusb_error(int err);