1#ifndef __TRIGGER_H_
 2#define __TRIGGER_H_ 1
 3
 4#include "util/debug.h"
 5#include "asm/bug.h"
 6
 7/*
 8 * Use trigger to model operations which need to be executed when
 9 * an event (a signal, for example) is observed.
10 *
11 * States and transits:
12 *
13 *
14 *  OFF--(on)--> READY --(hit)--> HIT
15 *                 ^               |
16 *                 |            (ready)
17 *                 |               |
18 *                  \_____________/
19 *
20 * is_hit and is_ready are two key functions to query the state of
21 * a trigger. is_hit means the event already happen; is_ready means the
22 * trigger is waiting for the event.
23 */
24
25struct trigger {
26	volatile enum {
27		TRIGGER_ERROR		= -2,
28		TRIGGER_OFF		= -1,
29		TRIGGER_READY		= 0,
30		TRIGGER_HIT		= 1,
31	} state;
32	const char *name;
33};
34
35#define TRIGGER_WARN_ONCE(t, exp) \
36	WARN_ONCE(t->state != exp, "trigger '%s' state transist error: %d in %s()\n", \
37		  t->name, t->state, __func__)
38
39static inline bool trigger_is_available(struct trigger *t)
40{
41	return t->state >= 0;
42}
43
44static inline bool trigger_is_error(struct trigger *t)
45{
46	return t->state <= TRIGGER_ERROR;
47}
48
49static inline void trigger_on(struct trigger *t)
50{
51	TRIGGER_WARN_ONCE(t, TRIGGER_OFF);
52	t->state = TRIGGER_READY;
53}
54
55static inline void trigger_ready(struct trigger *t)
56{
57	if (!trigger_is_available(t))
58		return;
59	t->state = TRIGGER_READY;
60}
61
62static inline void trigger_hit(struct trigger *t)
63{
64	if (!trigger_is_available(t))
65		return;
66	TRIGGER_WARN_ONCE(t, TRIGGER_READY);
67	t->state = TRIGGER_HIT;
68}
69
70static inline void trigger_off(struct trigger *t)
71{
72	if (!trigger_is_available(t))
73		return;
74	t->state = TRIGGER_OFF;
75}
76
77static inline void trigger_error(struct trigger *t)
78{
79	t->state = TRIGGER_ERROR;
80}
81
82static inline bool trigger_is_ready(struct trigger *t)
83{
84	return t->state == TRIGGER_READY;
85}
86
87static inline bool trigger_is_hit(struct trigger *t)
88{
89	return t->state == TRIGGER_HIT;
90}
91
92#define DEFINE_TRIGGER(n) \
93struct trigger n = {.state = TRIGGER_OFF, .name = #n}
94#endif