Getting Started with QNX Neutrino - QNX Software Systems

Writing a resource manager
© 2009, QNX Software Systems GmbH & Co. KG.
resmgr_io_funcs_t I/O table
The second parameter is always a pointer to the message. Because the functions in the
table are there to handle different types of messages, the prototypes match the kind of
message that each function will handle.
The third parameter is a RESMGR_HANDLE_T structure called a handle — it’s used to
identify the device that this message was targeted at. We’ll see this later as well, when
we look at the attributes structure.
Finally, the last parameter is either “reserved” or an “extra” parameter for functions
that need some extra data. We’ll show the extra parameter as appropriate during our
discussions of the handler functions.
The I/O table is very similar in spirit to the connect functions table just shown above.
Here it is, from :
typedef struct _resmgr_io_funcs {
unsigned nfuncs;
int (*read) (ctp, io_read_t *msg, ocb);
int (*write) (ctp, io_write_t *msg, ocb);
int (*close_ocb) (ctp, void *reserved, ocb);
int (*stat) (ctp, io_stat_t *msg, ocb);
int (*notify) (ctp, io_notify_t *msg, ocb);
int (*devctl) (ctp, io_devctl_t *msg, ocb);
int (*unblock) (ctp, io_pulse_t *msg, ocb);
int (*pathconf) (ctp, io_pathconf_t *msg, ocb);
int (*lseek) (ctp, io_lseek_t *msg, ocb);
int (*chmod) (ctp, io_chmod_t *msg, ocb);
int (*chown) (ctp, io_chown_t *msg, ocb);
int (*utime) (ctp, io_utime_t *msg, ocb);
int (*openfd) (ctp, io_openfd_t *msg, ocb);
int (*fdinfo) (ctp, io_fdinfo_t *msg, ocb);
int (*lock) (ctp, io_lock_t *msg, ocb);
int (*space) (ctp, io_space_t *msg, ocb);
int (*shutdown) (ctp, io_shutdown_t *msg, ocb);
int (*mmap) (ctp, io_mmap_t *msg, ocb);
int (*msg) (ctp, io_msg_t *msg, ocb);
int (*dup) (ctp, io_dup_t *msg, ocb);
int (*close_dup) (ctp, io_close_t *msg, ocb);
int (*lock_ocb) (ctp, void *reserved, ocb);
int (*unlock_ocb) (ctp, void *reserved, ocb);
int (*sync) (ctp, io_sync_t *msg, ocb);
} resmgr_io_funcs_t;
For this structure as well, I’ve shortened the prototype by removing the type of the ctp
member (resmgr_context_t *) and the last member (ocb, of type RESMGR_OCB_T
*). For example, the full prototype for read is really:
int (*read) (resmgr_context_t *ctp,
io_read_t *msg,
RESMGR_OCB_T *ocb);
The very first member of the structure (nfuncs) indicates how big the structure is (how
many members it contains). The proper manifest constant for initialization is
_RESMGR_IO_NFUNCS.
Note that the parameter list in the I/O table is also very regular. The first parameter is
the ctp, and the second parameter is the msg, just as they were in the connect table
handlers.
208 Chapter 5 • Resource Managers April 30, 2009