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Manual page for chpoll(9E)

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).

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

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 should only be called with one event at a time.

RETURN VALUES

chpoll() should return 0 for success, or the appropriate error number.

NOTES

Driver defined locks should not be held across calls to this function.

Last modified 21/April/97