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1libtraceevent(3)
2================
3
4NAME
5----
6tep_register_event_handler, tep_unregister_event_handler - Register /
7unregisters a callback function to parse an event information.
8
9SYNOPSIS
10--------
11[verse]
12--
13*#include <event-parse.h>*
14
15enum *tep_reg_handler* {
16 _TEP_REGISTER_SUCCESS_,
17 _TEP_REGISTER_SUCCESS_OVERWRITE_,
18};
19
20int *tep_register_event_handler*(struct tep_handle pass:[*]_tep_, int _id_, const char pass:[*]_sys_name_, const char pass:[*]_event_name_, tep_event_handler_func _func_, void pass:[*]_context_);
21int *tep_unregister_event_handler*(struct tep_handle pass:[*]tep, int id, const char pass:[*]sys_name, const char pass:[*]event_name, tep_event_handler_func func, void pass:[*]_context_);
22
23typedef int (*pass:[*]tep_event_handler_func*)(struct trace_seq pass:[*]s, struct tep_record pass:[*]record, struct tep_event pass:[*]event, void pass:[*]context);
24--
25
26DESCRIPTION
27-----------
28The _tep_register_event_handler()_ function registers a handler function,
29which is going to be called to parse the information for a given event.
30The _tep_ argument is the trace event parser context. The _id_ argument is
31the id of the event. The _sys_name_ argument is the name of the system,
32the event belongs to. The _event_name_ argument is the name of the event.
33If _id_ is >= 0, it is used to find the event, otherwise _sys_name_ and
34_event_name_ are used. The _func_ is a pointer to the function, which is going
35to be called to parse the event information. The _context_ argument is a pointer
36to the context data, which will be passed to the _func_. If a handler function
37for the same event is already registered, it will be overridden with the new
38one. This mechanism allows a developer to override the parsing of a given event.
39If for some reason the default print format is not sufficient, the developer
40can register a function for an event to be used to parse the data instead.
41
42The _tep_unregister_event_handler()_ function unregisters the handler function,
43previously registered with _tep_register_event_handler()_. The _tep_ argument
44is the trace event parser context. The _id_, _sys_name_, _event_name_, _func_,
45and _context_ are the same arguments, as when the callback function _func_ was
46registered.
47
48The _tep_event_handler_func_ is the type of the custom event handler
49function. The _s_ argument is the trace sequence, it can be used to create a
50custom string, describing the event. A _record_ to get the event from is passed
51as input parameter and also the _event_ - the handle to the record's event. The
52_context_ is custom context, set when the custom event handler is registered.
53
54RETURN VALUE
55------------
56The _tep_register_event_handler()_ function returns _TEP_REGISTER_SUCCESS_
57if the new handler is registered successfully or
58_TEP_REGISTER_SUCCESS_OVERWRITE_ if an existing handler is overwritten.
59If there is not enough memory to complete the registration,
60TEP_ERRNO__MEM_ALLOC_FAILED is returned.
61
62The _tep_unregister_event_handler()_ function returns 0 if _func_ was removed
63successful or, -1 if the event was not found.
64
65The _tep_event_handler_func_ should return -1 in case of an error,
66or 0 otherwise.
67
68EXAMPLE
69-------
70[source,c]
71--
72#include <event-parse.h>
73#include <trace-seq.h>
74...
75struct tep_handle *tep = tep_alloc();
76...
77int timer_expire_handler(struct trace_seq *s, struct tep_record *record,
78 struct tep_event *event, void *context)
79{
80 trace_seq_printf(s, "hrtimer=");
81
82 if (tep_print_num_field(s, "0x%llx", event, "timer", record, 0) == -1)
83 tep_print_num_field(s, "0x%llx", event, "hrtimer", record, 1);
84
85 trace_seq_printf(s, " now=");
86
87 tep_print_num_field(s, "%llu", event, "now", record, 1);
88
89 tep_print_func_field(s, " function=%s", event, "function", record, 0);
90
91 return 0;
92}
93...
94 int ret;
95
96 ret = tep_register_event_handler(tep, -1, "timer", "hrtimer_expire_entry",
97 timer_expire_handler, NULL);
98 if (ret < 0) {
99 char buf[32];
100
101 tep_strerror(tep, ret, buf, 32)
102 printf("Failed to register handler for hrtimer_expire_entry: %s\n", buf);
103 } else {
104 switch (ret) {
105 case TEP_REGISTER_SUCCESS:
106 printf ("Registered handler for hrtimer_expire_entry\n");
107 break;
108 case TEP_REGISTER_SUCCESS_OVERWRITE:
109 printf ("Overwrote handler for hrtimer_expire_entry\n");
110 break;
111 }
112 }
113...
114 ret = tep_unregister_event_handler(tep, -1, "timer", "hrtimer_expire_entry",
115 timer_expire_handler, NULL);
116 if ( ret )
117 printf ("Failed to unregister handler for hrtimer_expire_entry\n");
118
119--
120
121FILES
122-----
123[verse]
124--
125*event-parse.h*
126 Header file to include in order to have access to the library APIs.
127*trace-seq.h*
128 Header file to include in order to have access to trace sequences
129 related APIs. Trace sequences are used to allow a function to call
130 several other functions to create a string of data to use.
131*-ltraceevent*
132 Linker switch to add when building a program that uses the library.
133--
134
135SEE ALSO
136--------
137_libtraceevent(3)_, _trace-cmd(1)_
138
139AUTHOR
140------
141[verse]
142--
143*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
144*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
145--
146REPORTING BUGS
147--------------
148Report bugs to <linux-trace-devel@vger.kernel.org>
149
150LICENSE
151-------
152libtraceevent is Free Software licensed under the GNU LGPL 2.1
153
154RESOURCES
155---------
156https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git