Motorola MCP750 Specifications download pdf (Page 164)

evice Driver Programming

10-18

The Chpoll Routine 10

Speciﬁcation

#include <sys/types.h>

#include <sys/errno.h>

#include <sys/file.h>

#include <sys/cred.h>

#include <sys/ddi.h>

int xxchpoll (dev, events, anyyet, reventsp, phpp)

dev_t dev;

int events;

void * anyyet;

int reventsp;

cred_t *phpp;

Return Values

• 0 if the poll is successful

• A nonzero value if the poll fails. The number is returned to the user in

errno; it should be an error number as deﬁned in <sys/errno.h>.

The device driver’s chpoll routine is called when a poll(2) system call is made on

the associated device. The poll entry point is optional. It is valid for character device driv-

ers only.

The dev argument specifies the device major and minor number.

The events argument specifies a bit mask that indicates the I/O event(s) for which the

specified device is being polled. One or more of the following bits might be set:

POLLIN Data can be read from the device

POLLOUT Data can be written to the device

The anyyet argument specifies a flag that indicates whether or not I/O events are pending

for other devices that were specified on the poll(2) system call.

The reventsp argument is a pointer to a bit mask that indicates which requested I/O events

have occurred on the specified device. If an error has occurred on the device, the appropri-

ate error bit is set. One or more of the following bits might be set:

POLLIN Data can be read from the device

POLLOUT Data can be written to the device

POLLERR An error has occurred on the device

The phpp argument points to a pointer to a pollhead structure. This structure is defined

in <sys/poll.h>. The pollhead structure is not used by the device driver; it is used

by the poll service to monitor the I/O events for which the device is being polled.

The driver allocates a pollhead structure for each minor number of the device. The

pollhead structure might be a part of a driver data structure that is associated with the

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Motorola MCP750 Specifications Page 164