Install, poll, or remove a notification handler
#include <sys/iofunc.h>
int iofunc_notify( resmgr_context_t *ctp,
io_notify_t *msg,
iofunc_notify_t *nop,
int trig,
const int *notifycounts,
int *armed );
- ctp
- A pointer to a
resmgr_context_t
structure that the resource-manager library uses to pass context information
between functions.
- msg
- A pointer to the
io_notify_t
structure that contains
the message that the resource manager received; see below.
- nop
- An array of three
iofunc_notify_t
structures that represent, in order, the input, output, and out-of-band notification
lists; see below.
Generally, this structure is maintained by the resource manager
within an extended attributes structure.
- trig
- A bitmask indicating which sources are currently satisfied, and could
cause a trigger to occur.
This bitmask is any combination of
_NOTIFY_COND_INPUT, _NOTIFY_COND_OUTPUT and
_NOTIFY_COND_OBAND.
You typically set this value, based on the conditions in effect at
the time of the call.
- notifycounts
- NULL, or an array of three integers representing, in order,
the number of elements that must be present in the inout, output, and out-of-band queues
in order for the event to be triggered.
Note that if any condition is
met, nothing is armed. Only if none of the conditions are met, does the
event get armed in accordance with the notifycounts parameter. If this
parameter is NULL, a value of 1 is assumed
for all counts.
- armed
- NULL, or a pointer to a location where the function can
store a 1 to indicate that a notification entry is armed, or a
0 otherwise.
libc
Use the -l c option to
qcc
to link against this library.
This library is usually included automatically.
The POSIX layer helper function iofunc_notify() is used by a
resource manager to implement notification.
This routine examines the message that the resource manager received (passed
in the msg argument), and determines what action the client
code is attempting to perform:
- _NOTIFY_ACTION_POLL
- Return a one-part IOV with the flags field set to indicate
which conditions are available.
The caller should return
(_RESMGR_NPARTS(1))
to the resource manager library, which returns a one-part
message to the client.
- _NOTIFY_ACTION_POLLARM
- Similar to _NOTIFY_ACTION_POLL, with the
additional characteristic of arming the event if none of the
conditions is met.
- _NOTIFY_ACTION_TRANARM
- For each of the sources specified, create a notification entry
and store the client's struct sigevent event
structure in it.
Note that only one transition arm is allowed at a time per device.
If the client specifies an event of SIGEV_NONE, the
action is to disarm.
When the event is triggered, the notification is automatically disarmed.
- _NOTIFY_ACTION_CONDARM
- If the conditions aren't met, arm the event and return EAGAIN;
if the conditions are met, return a one-part IOV with the flags
field set to indicate which conditions are available.
The io_notify_t structure holds the _IO_NOTIFY
message received by the resource manager:
struct _io_notify {
uint16_t type;
uint16_t combine_len;
int32_t action;
int32_t flags;
struct sigevent event;
};
struct _io_notify_reply {
uint32_t zero;
uint32_t flags;
};
typedef union {
struct _io_notify i;
struct _io_notify_reply o;
} io_notify_t;
The I/O message structures are unions of an input message (coming to the
resource manager) and an output or reply message (going back to the client).
The i member is a structure of type _io_notify that
contains the following members:
- type
- _IO_NOTIFY.
- combine_len
- If the message is a combine message, _IO_COMBINE_FLAG
is set in this member.
For more information, see
Combine Messages
chapter of Writing a Resource Manager.
- action
- _NOTIFY_ACTION_POLL, _NOTIFY_ACTION_POLLARM,
_NOTIFY_ACTION_TRANARM, or _NOTIFY_ACTION_CONDARM, as described above.
- flags
- One of the following:
- _NOTIFY_COND_INPUT — this condition is met when
there are one or more units of input data available
(i.e. clients can now issue reads).
- _NOTIFY_COND_OUTPUT —
this condition is met when there's room in the output buffer
for one or more units of data (i.e. clients can now issue writes).
- _NOTIFY_COND_OBAND —
the condition is met when one or more units of out-of-band data are
available.
- event
- A pointer to a
sigevent
structure that defines the event that the resource manager is to deliver
once a condition is met.
The o member is a structure of type _io_notify_reply that
contains the following members:
- flags
- Which of the conditions were triggered; see the flags for
_io_notify, above.
The iofunc_notify_t structure is defined in
<sys/iofunc.h> as follows:
typedef struct _iofunc_notify {
int cnt;
struct _iofunc_notify_event *list;
} iofunc_notify_t;
The members of the iofunc_notify_t structure include:
- cnt
- The smallest cnt member in the list; see below.
- list
- A pointer to a linked list of iofunc_notify_event_t
structures that represent (in order), the input, output, and out-of-band
notification lists.
The iofunc_notify_event_t structure is defined as:
typedef struct _iofunc_notify_event {
struct _iofunc_notify_event *next;
int rcvid;
int scoid;
int cnt;
struct sigevent event;
unsigned flags;
int coid;
} iofunc_notify_event_t;
The members of the iofunc_notify_event_t structure include:
- next
- A pointer to the next element in the list.
- rcvid
- The receive ID of the client to notify.
- scoid
- The server connection ID.
- cnt
- The number of bytes available.
Some clients, such as io-char, may want a sufficiently large
amount of data to be available before they access it.
- event
- A pointer to a
sigevent
structure that defines the event that the resource manager is to deliver
once a condition is met.
- flags
- Used internally.
- coid
- The connection ID.
The sys/iofunc.h file also defines the following macros
that work with the arrays of iofunc_notify_t structures:
- #define IOFUNC_NOTIFY_DISARM(__nop, __index) ...
- Disarm the list specified by __index in __nop.
- #define IOFUNC_NOTIFY_INIT(__nop) ...
- Initialize the three lists in __nop.
- -1
- Success; the resource manager library should return a one-part IOV to
the client.
- EAGAIN
- The action was _NOTIFY_ACTION_CONDARM, and the conditions weren't met.
- EBUSY
- A notification was already armed for this resource, and this library function
enforces a restriction of one per resource.
- EINVAL
- Invalid action.
- ENOMEM
- There wasn't enough memory available to create an
iofunc_notify_event_t structure.
See
Writing a Resource Manager.
QNX Neutrino
Safety: | |
Cancellation point |
No |
Interrupt handler |
No |
Signal handler |
Yes |
Thread |
Yes |
iofunc_notify_remove(),
iofunc_notify_trigger(),
_RESMGR_NPARTS(),
sigevent
“Handling ionotify() and select()”
in the Handling Other Messages
chapter of Writing a Resource Manager
Resource Managers
chapter of Getting Started with QNX Neutrino