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7 .TH DDI_PERIODIC_ADD 9F "Jul 23, 2013"
8 .SH NAME
9 ddi_periodic_add \- request periodic function invocation
10 .SH SYNOPSIS
11 .LP
12 .nf
13 #include <sys/dditypes.h>
14 #include <sys/sunddi.h>
15
16 \fBddi_periodic_t\fR \fBddi_periodic_add\fR(\fBvoid (*\fR\fIfunc\fR)(\fBvoid *)\fR, \fBvoid\fR \fIarg\fR,
17 \fBhrtime_t\fR \fIinterval\fR, \fBint\fR \fIlevel\fR);
18 .fi
19
20 .SH INTERFACE LEVEL
21 .sp
22 .LP
23 Solaris DDI specific (Solaris DDI)
24 .SH PARAMETERS
25 .sp
26 .ne 2
27 .na
28 \fB\fIfunc\fR\fR
29 .ad
30 .RS 12n
31 The callback function to be invoked periodically in the specified interval.
32 .RE
33
34 .sp
35 .ne 2
36 .na
37 \fB\fIarg\fR\fR
38 .ad
39 .RS 12n
40 The argument passed to the callback function.
41 .RE
42
43 .sp
44 .ne 2
45 .na
46 \fB\fIinterval\fR\fR
47 .ad
48 .RS 12n
49 The periodic interval time in nanoseconds.
50 .RE
51
52 .sp
53 .ne 2
54 .na
55 \fB\fIlevel\fR\fR
56 .ad
57 .RS 12n
58 The callback function is invoked at this priority level. If the value of
59 \fIlevel\fR is zero, the callback function is invoked in kernel context.
60 If the value is greater than zero, but less than or equal to ten, the callback
61 function is invoked in interrupt context at the specified interrupt level,
62 which may be used for real time applications.
63 .sp
64 This value must be in range of 0-10, which can be either an integer literal, a
65 pre-defined macro (\fBDDI_IPL_0\fR, ... , \fBDDI_IPL_10\fR), or the
66 \fBDDI_INTR_PRI\fR macro with the interrupt priority.
67 .RE
68
69 .SH DESCRIPTION
70 .sp
71 .LP
72 The \fBddi_periodic_add()\fR function schedules the specified function to be
73 periodically invoked in the nanosecond interval time.
74 .sp
75 .LP
76 As with \fBtimeout\fR(9F), the exact time interval over which the function
77 takes effect cannot be guaranteed, but the value given is a close
78 approximation. If the callback function has not finished execution when the
79 next interval expires, the system will skip running the callback for that
80 interval.
81 .SH RETURN VALUES
82 .sp
83 .LP
84 \fBddi_periodic_add()\fR returns the non-zero opaque value
85 (\fBddi_periodic_t\fR), which is later used to cancel the periodic request
86 with \fBddi_periodic_delete\fR(9F).
87 .SH CONTEXT
88 .sp
89 .LP
90 The \fBddi_periodic_add()\fR function may be called from user or kernel
91 context.
92 .SH EXAMPLES
93 .LP
94 \fBExample 1 \fRUsing \fBddi_periodic_add()\fR for a periodic callback function
95 .sp
96 .LP
97 In the following example, the device driver registers a periodic callback
98 function invoked in kernel context.
99
100 .sp
101 .in +2
102 .nf
103 static void
104 my_periodic_func(void *arg)
105 {
106 /*
107 * This handler is invoked periodically.
108 */
109 struct my_state *statep = (struct my_state *)arg;
110
111 mutex_enter(&statep->lock);
112 if (load_unbalanced(statep)) {
113 balance_tasks(statep);
114 }
115 mutex_exit(&statep->lock);
116 }
117
118 static void
119 start_periodic_timer(struct my_state *statep)
120 {
121 hrtime_t interval = CHECK_INTERVAL;
122
123 mutex_init(&statep->lock, NULL, MUTEX_DRIVER, DDI_IPL_0);
124
125 /*
126 * Register my_callback which is invoked periodically
127 * in CHECK_INTERVAL in kernel context.
128 */
129 statep->periodic_id = ddi_periodic_add(my_periodic_func,
130 statep, interval, DDI_IPL_0);
131 .fi
132 .in -2
133
134 .sp
135 .LP
136 In the following example, the device driver registers a callback function
137 invoked in interrupt context at level 7.
138 .sp
139 .in +2
140 .nf
141 /*
142 * This handler is invoked periodically in interrupt context.
143 */
144 static void
145 my_periodic_int7_func(void *arg)
146 {
147 struct my_state *statep = (struct my_state *)arg;
148 mutex_enter(&statep->lock);
149 monitor_device(statep);
150 mutex_exit(&statep->lock);
151 }
152
153 static void
154 start_monitor_device(struct my_state *statep)
155 {
156 hrtime_t interval = MONITOR_INTERVAL;
157
158 mutex_init(&statep->lock, NULL, MUTEX_DRIVER, DDI_IPL_7);
159
160 /*
161 * Register the callback function invoked periodically
162 * at interrupt level 7.
163 */
164 statep->periodic_id = ddi_periodic_add(my_periodic_int7_func,
165 statep, interval, DDI_IPL_7);
166 }
167 .fi
168 .in -2
169
170 .SH SEE ALSO
171 .sp
172 .LP
173 \fBcv_timedwait\fR(9F), \fBddi_intr_get_pri\fR(9F),
174 \fBddi_periodic_delete\fR(9F), \fBddi_intr_get_softint_pri\fR(9F),
175 \fBqtimeout\fR(9F), \fBquntimeout\fR(9F), \fBtimeout\fR(9F), \fBuntimeout\fR(9F)
176 .SH NOTES
177 .sp
178 .LP
179 The caller must specify \fIinterval\fR as an even, non-zero multiple of 10ms.
180 No other values are supported at this time. The interval specified is a lower
181 bound on the interval between executions of the callback.