When generating custom hardware and drivers for Qsys, the following warning may be seen in the Nios® II BSP Editor, resulting in the driver being unavailable for a given hardware instance:
WARNING: Hardware component "myhardware:3.2" does not meet candidate driver "myhardware_driver:3.2" stated minimal compatible hardware version "7.1". You may need to re-generate the SOPC system to get updated hardware versions.
If the user has not specified the minimum compatible hardware version number for their software, the Nios II Software Build Tools assume that hardware has to be of version 7.1 or greater. If your hardware version number is lower than 7.1, this will cause a warning, and the driver will not be available for use.
To resolve this issue, add the min_compatible_hw_version software property to the drivers _sw.tcl file as illustrated below:
set_sw_property min_compatible_hw_version 3.2
The version number specified should be the lowest hardware version that is supported by the driver. Further details about the min_comatible_hw_version property can be found in the Nios II Software Developers Handbook.