32-bit and 64-bit Data Structure Macros

The method in Example 15–15 works well for many drivers. An alternate scheme is to use the data structure macros that are provided in <sys/model.h>to move data between the application and the kernel. These macros make the code less cluttered and behave identically, from a functional perspective.

int
    xxioctl(dev_t dev, int cmd, intptr_t arg, int mode,
        cred_t *cr, int *rval_p)
    {    
        STRUCT_DECL(opdata, op);

        if (cmd != OPONE)
            return (ENOTTY);

        STRUCT_INIT(op, mode);

        if (copyin((void *)arg,
            STRUCT_BUF(op), STRUCT_SIZE(op)))
                return (EFAULT);

        if (STRUCT_FGET(op, flag) != XXACTIVE ||     
            STRUCT_FGET(op, size) > XXSIZE)
                return (EINVAL);
        xxdowork(device_state, STRUCT_FGET(op, size));
        return (0);
}