FreeBSD Device Drivers

Hello, world!

You now know enough to write your first KLD. Example 1-1 is the complete skeleton code for a KLD.

Example 1-1. hello.c

#include <sys/param.h>
  #include <sys/module.h>
  #include <sys/kernel.h>
  #include <sys/systm.h>

  static int
 hello_modevent(module_t mod __unused, int event, void *arg __unused)
  {
          int error = 0;

          switch (event) {
          case MOD_LOAD:
                  uprintf("Hello, world!\n");
                  break;
          case MOD_UNLOAD:
                  uprintf("Good-bye, cruel world!\n");
                  break;
          default:
                  error = EOPNOTSUPP;
                  break;
          }

          return (error);
  }

 static moduledata_t hello_mod = { "hello", hello_modevent, ...