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);

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. 

SEE ALSO

poll(2), pollwakeup(9F)

Writing Device Drivers

NOTES

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

SunOS 5.5/x86  —  Last change: 11 Apr 1991