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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).

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);

    .
  1. 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.
    2. .
  2. 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.

See Also

poll(2) , nochpoll(9F) , pollwakeup(9F)

Notes

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

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