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 157