1chpoll(9E) Driver Entry Points chpoll(9E)
2
6 chpoll - poll entry point for a non-STREAMS character driver
7
9 #include <sys/types.h>
10 #include <sys/poll.h>
11 #include <sys/ddi.h>
12 #include <sys/sunddi.h>
13 int prefixchpoll(dev_t dev, short events, int anyyet,
17 short *reventsp, struct pollhead **phpp);
18
21 This entry point is optional. Architecture independent level 1
22 (DDI/DKI).
23
25 dev The device number for the device to be polled.
26 events The events that may occur. Valid events are:
29 POLLIN Data other than high priority data may be
31 read without blocking.
32 POLLOUT Normal data may be written without blocking.
35 POLLPRI High priority data may be received without
38 blocking.
39 POLLHUP A device hangup has occurred.
42 POLLERR An error has occurred on the device.
45 POLLRDNORM Normal data (priority band = 0) may be read
48 without blocking.
49 POLLRDBAND Data from a non-zero priority band may be
52 read without blocking
53 POLLWRNORM The same as POLLOUT.
56 POLLWRBAND Priority data (priority band > 0) may be
59 written.
60 anyyet A flag that is non-zero if any other file descriptors in
64 the pollfd array have events pending. The poll(2) system
65 call takes a pointer to an array of pollfd structures as
66 one of its arguments. See the poll(2) reference page for
67 more details.
68 reventsp A pointer to a bitmask of the returned events satisfied.
71 phpp A pointer to a pointer to a pollhead structure.
74
77 The chpoll() entry point routine is used by non-STREAMS character
78 device drivers that wish to support polling. The driver must implement
79 the polling discipline itself. The following rules must be followed
80 when implementing the polling discipline:
81 1. Implement the following algorithm when the chpoll() entry
83 point is called:
84 if (events_are_satisfied_now) {
86 *reventsp = satisfied_events & events;
87 } else {
88 *reventsp = 0;
89 if (!anyyet)
90 *phpp = &my_local_pollhead_structure;
91 }
92 return (0);
93 2. Allocate an instance of the pollhead structure. This
96 instance may be tied to the per-minor data structure defined
97 by the driver. The pollhead structure should be treated as a
98 "black box" by the driver. Initialize the pollhead structure
99 by filling it with zeroes. The size of this structure is
100 guaranteed to remain the same across releases.
101 3. Call the pollwakeup() function with events listed above
103 whenever pollable events which the driver should monitor
104 occur. This function can be called with multiple events at
105 one time. The pollwakup() can be called regardless of
106 whether or not the chpoll() entry is called; it should be
107 called every time the driver detects the pollable event. The
108 driver must not hold any mutex across the call to poll‐
109 wakeup(9F) that is acquired in its chpoll() entry point, or
110 a deadlock may result.
111
113 chpoll() should return 0 for success, or the appropriate error number.
114
116 poll(2), nochpoll(9F), pollwakeup(9F)
117 Writing Device Drivers
120SunOS 5.11 7 May 2008 chpoll(9E)