Commit | Line | Data |
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9cfe06f8 SR |
1 | /* |
2 | * If TRACE_SYSTEM is defined, that will be the directory created | |
088a4eed | 3 | * in the ftrace directory under /sys/kernel/debug/tracing/events/<system> |
9cfe06f8 | 4 | * |
44ad18e0 | 5 | * The define_trace.h below will also look for a file name of |
9cfe06f8 | 6 | * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here. |
44ad18e0 | 7 | * In this case, it would look for sample.h |
9cfe06f8 | 8 | * |
44ad18e0 SR |
9 | * If the header name will be different than the system name |
10 | * (as in this case), then you can override the header name that | |
11 | * define_trace.h will look up by defining TRACE_INCLUDE_FILE | |
9cfe06f8 | 12 | * |
44ad18e0 SR |
13 | * This file is called trace-events-sample.h but we want the system |
14 | * to be called "sample". Therefore we must define the name of this | |
15 | * file: | |
9cfe06f8 | 16 | * |
44ad18e0 | 17 | * #define TRACE_INCLUDE_FILE trace-events-sample |
9cfe06f8 | 18 | * |
44ad18e0 | 19 | * As we do an the bottom of this file. |
d0b6e04a LZ |
20 | * |
21 | * Notice that TRACE_SYSTEM should be defined outside of #if | |
22 | * protection, just like TRACE_INCLUDE_FILE. | |
9cfe06f8 SR |
23 | */ |
24 | #undef TRACE_SYSTEM | |
71e1c8ac | 25 | #define TRACE_SYSTEM sample |
9cfe06f8 | 26 | |
d0b6e04a LZ |
27 | /* |
28 | * Notice that this file is not protected like a normal header. | |
29 | * We also must allow for rereading of this file. The | |
30 | * | |
31 | * || defined(TRACE_HEADER_MULTI_READ) | |
32 | * | |
33 | * serves this purpose. | |
34 | */ | |
35 | #if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ) | |
36 | #define _TRACE_EVENT_SAMPLE_H | |
37 | ||
38 | /* | |
39 | * All trace headers should include tracepoint.h, until we finally | |
40 | * make it into a standard header. | |
41 | */ | |
42 | #include <linux/tracepoint.h> | |
43 | ||
9cfe06f8 SR |
44 | /* |
45 | * The TRACE_EVENT macro is broken up into 5 parts. | |
46 | * | |
47 | * name: name of the trace point. This is also how to enable the tracepoint. | |
48 | * A function called trace_foo_bar() will be created. | |
49 | * | |
50 | * proto: the prototype of the function trace_foo_bar() | |
51 | * Here it is trace_foo_bar(char *foo, int bar). | |
52 | * | |
53 | * args: must match the arguments in the prototype. | |
54 | * Here it is simply "foo, bar". | |
55 | * | |
56 | * struct: This defines the way the data will be stored in the ring buffer. | |
57 | * There are currently two types of elements. __field and __array. | |
58 | * a __field is broken up into (type, name). Where type can be any | |
59 | * type but an array. | |
60 | * For an array. there are three fields. (type, name, size). The | |
61 | * type of elements in the array, the name of the field and the size | |
62 | * of the array. | |
63 | * | |
64 | * __array( char, foo, 10) is the same as saying char foo[10]. | |
65 | * | |
66 | * fast_assign: This is a C like function that is used to store the items | |
67 | * into the ring buffer. | |
68 | * | |
69 | * printk: This is a way to print out the data in pretty print. This is | |
70 | * useful if the system crashes and you are logging via a serial line, | |
71 | * the data can be printed to the console using this "printk" method. | |
72 | * | |
73 | * Note, that for both the assign and the printk, __entry is the handler | |
74 | * to the data structure in the ring buffer, and is defined by the | |
75 | * TP_STRUCT__entry. | |
76 | */ | |
77 | TRACE_EVENT(foo_bar, | |
78 | ||
79 | TP_PROTO(char *foo, int bar), | |
80 | ||
81 | TP_ARGS(foo, bar), | |
82 | ||
83 | TP_STRUCT__entry( | |
84 | __array( char, foo, 10 ) | |
85 | __field( int, bar ) | |
86 | ), | |
87 | ||
88 | TP_fast_assign( | |
89 | strncpy(__entry->foo, foo, 10); | |
90 | __entry->bar = bar; | |
91 | ), | |
92 | ||
93 | TP_printk("foo %s %d", __entry->foo, __entry->bar) | |
94 | ); | |
95 | #endif | |
96 | ||
97 | /***** NOTICE! The #if protection ends here. *****/ | |
98 | ||
99 | ||
100 | /* | |
101 | * There are several ways I could have done this. If I left out the | |
102 | * TRACE_INCLUDE_PATH, then it would default to the kernel source | |
103 | * include/trace/events directory. | |
104 | * | |
105 | * I could specify a path from the define_trace.h file back to this | |
106 | * file. | |
107 | * | |
108 | * #define TRACE_INCLUDE_PATH ../../samples/trace_events | |
109 | * | |
44ad18e0 SR |
110 | * But the safest and easiest way to simply make it use the directory |
111 | * that the file is in is to add in the Makefile: | |
9cfe06f8 | 112 | * |
44ad18e0 | 113 | * CFLAGS_trace-events-sample.o := -I$(src) |
9cfe06f8 SR |
114 | * |
115 | * This will make sure the current path is part of the include | |
44ad18e0 | 116 | * structure for our file so that define_trace.h can find it. |
9cfe06f8 SR |
117 | * |
118 | * I could have made only the top level directory the include: | |
119 | * | |
120 | * CFLAGS_trace-events-sample.o := -I$(PWD) | |
121 | * | |
122 | * And then let the path to this directory be the TRACE_INCLUDE_PATH: | |
123 | * | |
124 | * #define TRACE_INCLUDE_PATH samples/trace_events | |
125 | * | |
44ad18e0 SR |
126 | * But then if something defines "samples" or "trace_events" as a macro |
127 | * then we could risk that being converted too, and give us an unexpected | |
9cfe06f8 SR |
128 | * result. |
129 | */ | |
130 | #undef TRACE_INCLUDE_PATH | |
71e1c8ac | 131 | #undef TRACE_INCLUDE_FILE |
9cfe06f8 | 132 | #define TRACE_INCLUDE_PATH . |
71e1c8ac SR |
133 | /* |
134 | * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal | |
135 | */ | |
136 | #define TRACE_INCLUDE_FILE trace-events-sample | |
9cfe06f8 | 137 | #include <trace/define_trace.h> |