The key thing of RAsm plugin is a structure

    where .disassemble is a pointer to disassembly function, which accepts the bytes buffer and length:

    asm_mycpu.c

    After compiling radare2 will list this plugin in the output:

    List of affected files:

    • : build instructions
    • : add the struct definition in there

    Check out how the NIOS II CPU disassembly plugin was implemented by reading those commits:

    Implement RAnal plugin: