chpoll - poll entry point for a non-STREAMS character driver

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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

ARGUMENTS

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

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 should only be called with one event at a time.

RETURN VALUES

SEE ALSO

NOTES