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.

If you need to modify any members of the mount structure, use iofunc_mount_init() to initialize it.

For example, your program saves files to a file system. You can use iofunc_mount_init() and iofunc_mount_set_time() to set a timestamp resolution for open files that matches the resolution the file system uses (a POSIX requirement).

The iofunc_mount_t structure is optional and 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;
    void                *power;
    
    size_t              size;
    uint32_t            ex_flags;
    uint32_t            timeres;
    uint64_t            reserved[4];    
} iofunc_mount_t;

The variables are:

flags
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>).
conf
Contains several bits:
IOFUNC_PC_CHOWN_RESTRICTED
Causes the default handler for the _IO_CHOWN message to behave in a manner defined by POSIX as chown-restricted”.
IOFUNC_PC_NO_TRUNC
Has no effect on the iofunc layer libraries, but is returned by the iofunc layer's default _IO_PATHCONF handler.
IOFUNC_PC_SYNC_IO
Indicates that the filesystem supports synchronous I/O operations. If this bit isn't set, the following may occur:
IOFUNC_PC_LINK_DIR
Controls whether or not root is allowed to link and unlink directories.
IOFUNC_PC_ACL
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.
IOFUNC_PC_EXT
Set automatically when iofunc_mount_init() is called to set the iofunc_mount_t structure.

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

dev
Contains the device number for the filesystem. This number is returned to the client's stat() function in the struct stat st_dev member.
blocksize
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.
funcs
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);
   int          (*attr_lock)(IOFUNC_ATTR_T *attr);
   int          (*attr_unlock)(IOFUNC_ATTR_T *attr);
   int          (*attr_trylock)(IOFUNC_ATTR_T *attr);

};

where:

nfuncs
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.
attr_lock(), attr_unlock() and attr_trylock()
Allows you to create customized versions of the functions that lock, unlock, and attempt to lock the attribute structure.
power
Reserved for future use.
size
Contains the size of the iofunc_mount_t function. Set by iofunc_mount_init().
ext_flags
Extends the range of possible flags values.
timeres
Contains the timestamp resolution for iofunc functions and structures. Set by iofunc_mount_set_time().
reserved
Reserved for future use.