Getting Started with QNX Neutrino - QNX Software Systems

Alphabetical listing of connect and I/O functions
© 2009, QNX Software Systems GmbH & Co. KG.
member; the driver is to set the outgoing structure’s nbytes member to the number of
bytes transferred.
Note that the input and output data structures are zero-padded so that they align with
each other. This means that the implicit data area begins at the same address in the
input and output structures.
If using the helper routine iofunc_devctl(), beware that it’ll return the constant
_RESMGR_DEFAULT in the case where it can’t do anything with the devctl() message.
This return value is there to decouple legitimate errno return values from an
“unrecognized command” return value. Upon receiving a _RESMGR_DEFAULT, the
base-layer library will respond with an errno of ENOSYS, which the client’s devctl()
library function will translate into ENOTTY (which is the “correct” POSIX value).
It’s up to your function to check the open mode against the operation; no checking is
done anywhere in either the client’s devctl() library or in the resource manager library.
For example, it’s possible to open a resource manager “read-only” and then issue a
devctl() to it telling it to “format the hard disk” (which is very much a “write”
operation). It would be prudent to verify the open mode first before proceeding with
the operation.
Note that the range of dcmd values you can use is limited (0x0000 through 0x0FFF
inclusive is reserved for QSS). Other values may be in use; take a look through the
include files that have the name .
Returns: The status via the helper macro _RESMGR_STATUS and the reply buffer
(with reply data, if required).
For an example, take a look at “A simple io_devctl() example,” below.
io_dup()
int io_dup (resmgr_context_t *ctp, io_dup_t *msg, RESMGR_OCB_T
*ocb)
Classification: I/O
Default handler: NULL — handled by base layer
Helper functions: none
Client functions: dup(), dup2(), fcntl(), fork(), spawn*(), vfork()
Messages: _IO_DUP
Data structure:
struct _io_dup {
uint16_t
type;
uint16_t
combine_len;
struct _msg_info info;
uint32_t
reserved;
uint32_t
key;
};
typedef union {
234 Chapter 5 • Resource Managers April 30, 2009