A few years ago I bought a YardStick One from Great Scott Gadgets (https://greatscottgadgets.com/yardstickone/).
YardStick One works with a software suite called rfcat (https://github.com/atlas0fd00m/rfcat). I needed to update the bootloader firmware for my YardStick One to work with recent versions of rfcat.
Because of a compiler issue between sdcc 3.6.0.0 and 3.8.0.0 (latest as of this writing), when I attempted to flash the bootloader firmware, I received an Invalid IOCTL warning:
Could not configure port: (25, 'Inappropriate ioctl for device')
I had to use a custom build of the firmware, compiled against sdcc 3.6.0.0, in order for the YardStick One to work properly.
You can compile sdcc yourself at version 3.6.0.0 and then compile the bootloader in the rfcat source, or you can use the firmware here: https://gist.github.com/mossmann/7b816680df2ac513df3835f3cb9eaa1b
Hopefully this saves someone some time.