The macros STRUCT_DECL() and STRUCT_HANDLE() declare structure handles on the stack, whereas the macros STRUCT_INIT() and STRUCT_SET_HANDLE() initialize the structure handles to point to an instance of the native form structure.

The macros STRUCT_HANDLE() and STRUCT_SET_HANDLE() are used to declare and initialize a structure handle to an existing data structure, for example, ioctls within a STREAMS module.

The macros STRUCT_DECL() and STRUCT_INIT(), on the other hand, are used in modules which declare and initialize a structure handle to a data structure allocated by STRUCT_DECL(), that is, any standard character or block device driver ioctl(9E) routine that needs to copy in data from a user-mode program.

STRUCT_DECL(structname, handle)

Declares a structure handle for a struct and allocates an instance of its native form on the stack. It is assumed that the native form is larger than or equal to the ILP32 form. handle is a variable name and is declared as a variable by this macro.

void STRUCT_INIT(handle, model_t umodel)

Initializes handle to point to the instance allocated by STRUCT_DECL(), it also sets data model for handle to umodel, and must be called before any access is made through the macros that operate on these structures. When used in an ioctl(9E) routine umodel is the flag parameter; in adevmap(9E) routine umodel is the model parameter and in a mmap(9E) routine, is the return value of ddi_mmap_get_model(9F). This macro is intended for handles created with STRUCT_DECL() only.

STRUCT_HANDLE(structname, handle)

Declares a structure handle handle but unlike STRUCT_DECL() does not allocate an instance of "struct ".

void STRUCT_SET_HANDLE(handle, model_t umodel, void *addr)

Initializes to point to the native form instance at addr, it also sets the data model for handle to umodel. This is intended for handles created with STRUCT_HANDLE(). Fields cannot be referenced via the handle until this macro has been invoked. Typically, addr is the address of the native form structure containing the user-mode programs data. When used in an ioctl(9E) umodel is the flag parameter, in a devmap(9E) routine is the model parameter and in a mmap(9E) routine, umodel is the return value of ddi_mmap_get_model(9F).

size_t STRUCT_SIZE(handle)

Returns size of the structure referred to by handle. It will return the size depending upon the data model associated with handle. If the data model stored by STRUCT_INIT() or STRUCT_SET_HANDLE() was DATAMODEL_ILP32, it will return the size of the ILP32 form, else it will return the size of the native form.

STRUCT_FGET(handle, field)

Returns the contents of field in the structure described by handle according to the data model associated with handle.

STRUCT_FGETP(handle, field)

This is the same as STRUCT_FGET() except that the field in question is a pointer of some kind. This macro will cast caddr32_t to a (void *) when it is accessed. Failure to use this macro for a pointer will lead to compiler warnings or failures.

STRUCT_FSET(handle, field, val)

Assigns val to the (non pointer) in the structure handle described by . It should not be used within any other expression, but rather only as a statement.

STRUCT_FSETP(handle, field, val)

Returns a pointer to the in the structure described by handle.

struct structname *STRUCT_BUF(handle)

Returns a pointer to the native mode instance of the structure described by handle.

size_t SIZEOF_STRUCT(structname, umodel)

Returns size of structname based on umodel.

size_t SIZEOF_PTR(umodel)

Returns the size of a pointer based on umodel.

The following example uses an ioctl(9E) on a regular character device that copies a data structure that looks like this into the kernel:

struct opdata {
    size_t  size;
    uint_t  flag;
};

This data structure definition describes what the ioctl(9E) would look like in a 32-bit application using fixed width types.

#if defined(_MULTI_DATAMODEL)
struct opdata32 {
    size32_t    size;
    uint32_t    flag;
};
#endif

Note: This example uses the STRUCT_DECL() and STRUCT_INIT() macros to declare and initialize the structure handle.

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 *)data,
        STRUCT_BUF(op), STRUCT_SIZE(op)))
        return (EFAULT);

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

This piece of code is an excerpt from a STREAMS module that handles ioctl(9E) data (M_IOCDATA) messages and uses the data structure defined above. This code has been written to run in the ILP32 environment only.

The next example illustrates the use of the STRUCT_HANDLE() and STRUCT_SET_HANDLE() macros which declare and initialize the structure handle to point to an already existing instance of the structure.

The above code example can be converted to run in the LP64 environment using the STRUCT_HANDLE() and STRUCT_SET_HANDLE() as follows:

struct strbuf {
int maxlen;     /* no. of bytes in buffer */
int len;        /* no. of bytes returned */
caddr_t buf;        /* pointer to data */
};

static void
wput_iocdata(queue_t *q, mblk_t *msgp)
{
        mblk_t  *data;  /* message block descriptor */
        STRUCT_HANDLE(strbuf, sb);

    /* copyin the data */
    if (mi_copy_state(q, mp, &data) == -1) {
                return;
    }

        STRUCT_SET_HANDLE(sb,((struct iocblk *)msgp->b_rptr)->ioc_flag,
            (void *)data->b_rptr);
        if (STRUCT_FGET(sb, maxlen) < (int)sizeof (ipa_t)) {
                mi_copy_done(q, msgp, EINVAL);
        return;
    }
}