The optional iofunc_mount_t (mount) structure

The members of the mount structure, specifically the conf and flags members, modify the behavior of some of the iofunc layer functions. This optional structure contains at least the following:

typedef struct _iofunc_mount {
    uint32_t            flags;
    uint32_t            conf;
    dev_t               dev;
    int32_t             blocksize;
    iofunc_funcs_t      *funcs;
} iofunc_mount_t;

The variables are:

Contains one relevant bit (manifest constant IOFUNC_MOUNT_32BIT), which indicates that the offsets used by this resource manager are 32-bit (as opposed to the extended 64-bit offsets). The user-modifiable mount flags are defined as IOFUNC_MOUNT_FLAGS_PRIVATE (see <sys/iofunc.h>).
Contains several bits:
Causes the default handler for the _IO_CHOWN message to behave in a manner defined by POSIX as "chown-restricted".
Has no effect on the iofunc layer libraries, but is returned by the iofunc layer's default _IO_PATHCONF handler.
Indicates that the filesystem supports synchronous I/O operations. If this bit isn't set, the following may occur:
Controls whether or not root is allowed to link and unlink directories.
Indicates whether or not the resource manager supports access control lists. For more information about ACLs, see Working with Access Control Lists (ACLs) in the QNX Neutrino Programmer's Guide.

Note that the options mentioned above for the conf member are returned by the iofunc layer _IO_PATHCONF default handler.

Contains the device number for the filesystem. This number is returned to the client's stat() function in the struct stat st_dev member.
Contains the block size of the device. On filesystem types of resource managers, this indicates the native blocksize of the disk, e.g., 512 bytes.
Contains the following structure:
struct _iofunc_funcs {
   unsigned     nfuncs;
   IOFUNC_OCB_T *(*ocb_calloc) (resmgr_context_t *ctp,
                                IOFUNC_ATTR_T *attr);
   void         (*ocb_free) (IOFUNC_OCB_T *ocb);


Indicates the number of functions present in the structure; you should fill it with the manifest constant _IOFUNC_NFUNCS.
ocb_calloc() and ocb_free()
Allows you to override the OCBs on a per-mountpoint basis (see "Extending the OCB and attribute structures" in the Extending the POSIX-Layer Data Structures chapter). If these members are NULL, then the default library versions (iofunc_ocb_calloc() and iofunc_ocb_free()) are used. You must specify either both or neither of these functions; they operate as a matched pair.