chpoll(9E) Driver Entry Points chpoll(9E)NAMEchpoll - poll entry point for a non-STREAMS character driver
SYNOPSIS
#include <sys/types.h>
#include <sys/poll.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
int prefixchpoll(dev_t dev, short events, int anyyet,
short *reventsp, struct pollhead **phpp);
INTERFACE LEVEL
This entry point is optional. Architecture independent level 1
(DDI/DKI).
PARAMETERS
dev The device number for the device to be polled.
events The events that may occur. Valid events are:
POLLIN Data other than high priority data may be
read without blocking.
POLLOUT Normal data may be written without blocking.
POLLPRI High priority data may be received without
blocking.
POLLHUP A device hangup has occurred.
POLLERR An error has occurred on the device.
POLLRDNORM Normal data (priority band = 0) may be read
without blocking.
POLLRDBAND Data from a non-zero priority band may be
read without blocking
POLLWRNORM The same as POLLOUT.
POLLWRBAND Priority data (priority band > 0) may be
written.
anyyet A flag that is non-zero if any other file descriptors in
the pollfd array have events pending. The poll(2) system
call takes a pointer to an array of pollfd structures as
one of its arguments. See the poll(2) reference page for
more details.
reventsp A pointer to a bitmask of the returned events satisfied.
phpp A pointer to a pointer to a pollhead structure.
DESCRIPTION
The chpoll() entry point routine is used by non-STREAMS character
device drivers that wish to support polling. The driver must implement
the polling discipline itself. The following rules must be followed
when implementing the polling discipline:
1. Implement the following algorithm when the chpoll() entry
point is called:
if (events_are_satisfied_now) {
*reventsp = satisfied_events & events;
} else {
*reventsp = 0;
if (!anyyet)
*phpp = &my_local_pollhead_structure;
}
return (0);
2. Allocate an instance of the pollhead structure. This
instance may be tied to the per-minor data structure defined
by the driver. The pollhead structure should be treated as a
"black box" by the driver. Initialize the pollhead structure
by filling it with zeroes. The size of this structure is
guaranteed to remain the same across releases.
3. Call the pollwakeup() function with events listed above
whenever pollable events which the driver should monitor
occur. This function can be called with multiple events at
one time. The pollwakup() can be called regardless of
whether or not the chpoll() entry is called; it should be
called every time the driver detects the pollable event. The
driver must not hold any mutex across the call to poll‐
wakeup(9F) that is acquired in its chpoll() entry point, or
a deadlock may result.
RETURN VALUESchpoll() should return 0 for success, or the appropriate error number.
SEE ALSOpoll(2), nochpoll(9F), pollwakeup(9F)SunOS 5.10 7 May 2008 chpoll(9E)
