chpoll(9E) Driver Entry Points chpoll(9E)
NAME
chpoll - 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 = mask_of_satisfied_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. None of its fields should be referenced. However, the size of
this structure is guaranteed to remain the same across releases.
3. Call the pollwakeup() function whenever an event of type events listed above occur. This function can be called with multiple events at
one time. The driver must not hold any mutex across the call to pollwakeup(9F) that is acquired in its chpoll() entry point, or a dead-
lock may result.
RETURN VALUES
chpoll() should return 0 for success, or the appropriate error number.
SEE ALSO
poll(2), nochpoll(9F), pollwakeup(9F)
Writing Device Drivers
SunOS 5.10 8 Nov 2001 chpoll(9E)
