Yep, that is it. Also in espressif github issue tracker:

https://github.com/espressif/esp-idf/issues/2136

Regards, Mark.

On 15 Nov 2018, at 1:34 AM, Craig Leres <leres@xse.com> wrote:

On 11/14/18 4:09 AM, Mark Webb-Johnson wrote:
There seems to be a compilation warning:
   $ make -j 4
   Build version is 3.1.011-21-g5d46d82
   CXX build/main/ovms_version.o
   In file included from main/ovms_version.cpp:34:0:
   esp/esp-idf/components/bootloader_support/include/esp_image_format.h:44:3:
   warning: 'esp_image_spi_freq_t' defined but not used [-Wunused-variable]
     } esp_image_spi_freq_t;
       ^
I merged it, to allow further testing on ‘edge’ boxes, but it would be good if that could be cleaned up.

Sorry, when I hit this I fixed what looked like an obvious typo but didn't notice it was in esp-idf. Here's the pull request:

   https://github.com/openvehicles/esp-idf/pull/3/files

Craig