| libtraceevent(3) |
| ================ |
| |
| NAME |
| ---- |
| tep_register_event_handler, tep_unregister_event_handler - Register / |
| unregisters a callback function to parse an event information. |
| |
| SYNOPSIS |
| -------- |
| [verse] |
| -- |
| *#include <event-parse.h>* |
| |
| enum *tep_reg_handler* { |
| _TEP_REGISTER_SUCCESS_, |
| _TEP_REGISTER_SUCCESS_OVERWRITE_, |
| }; |
| |
| int *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_); |
| int *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_); |
| |
| typedef int (*pass:[*]tep_event_handler_func*)(struct trace_seq pass:[*]s, struct tep_record pass:[*]record, struct tep_event pass:[*]event, void pass:[*]context); |
| -- |
| |
| DESCRIPTION |
| ----------- |
| The _tep_register_event_handler()_ function registers a handler function, |
| which is going to be called to parse the information for a given event. |
| The _tep_ argument is the trace event parser context. The _id_ argument is |
| the id of the event. The _sys_name_ argument is the name of the system, |
| the event belongs to. The _event_name_ argument is the name of the event. |
| If _id_ is >= 0, it is used to find the event, otherwise _sys_name_ and |
| _event_name_ are used. The _func_ is a pointer to the function, which is going |
| to be called to parse the event information. The _context_ argument is a pointer |
| to the context data, which will be passed to the _func_. If a handler function |
| for the same event is already registered, it will be overridden with the new |
| one. This mechanism allows a developer to override the parsing of a given event. |
| If for some reason the default print format is not sufficient, the developer |
| can register a function for an event to be used to parse the data instead. |
| |
| The _tep_unregister_event_handler()_ function unregisters the handler function, |
| previously registered with _tep_register_event_handler()_. The _tep_ argument |
| is the trace event parser context. The _id_, _sys_name_, _event_name_, _func_, |
| and _context_ are the same arguments, as when the callback function _func_ was |
| registered. |
| |
| The _tep_event_handler_func_ is the type of the custom event handler |
| function. The _s_ argument is the trace sequence, it can be used to create a |
| custom string, describing the event. A _record_ to get the event from is passed |
| as input parameter and also the _event_ - the handle to the record's event. The |
| _context_ is custom context, set when the custom event handler is registered. |
| |
| RETURN VALUE |
| ------------ |
| The _tep_register_event_handler()_ function returns _TEP_REGISTER_SUCCESS_ |
| if the new handler is registered successfully or |
| _TEP_REGISTER_SUCCESS_OVERWRITE_ if an existing handler is overwritten. |
| If there is not enough memory to complete the registration, |
| TEP_ERRNO__MEM_ALLOC_FAILED is returned. |
| |
| The _tep_unregister_event_handler()_ function returns 0 if _func_ was removed |
| successful or, -1 if the event was not found. |
| |
| The _tep_event_handler_func_ should return -1 in case of an error, |
| or 0 otherwise. |
| |
| EXAMPLE |
| ------- |
| [source,c] |
| -- |
| #include <event-parse.h> |
| #include <trace-seq.h> |
| ... |
| struct tep_handle *tep = tep_alloc(); |
| ... |
| int timer_expire_handler(struct trace_seq *s, struct tep_record *record, |
| struct tep_event *event, void *context) |
| { |
| trace_seq_printf(s, "hrtimer="); |
| |
| if (tep_print_num_field(s, "0x%llx", event, "timer", record, 0) == -1) |
| tep_print_num_field(s, "0x%llx", event, "hrtimer", record, 1); |
| |
| trace_seq_printf(s, " now="); |
| |
| tep_print_num_field(s, "%llu", event, "now", record, 1); |
| |
| tep_print_func_field(s, " function=%s", event, "function", record, 0); |
| |
| return 0; |
| } |
| ... |
| int ret; |
| |
| ret = tep_register_event_handler(tep, -1, "timer", "hrtimer_expire_entry", |
| timer_expire_handler, NULL); |
| if (ret < 0) { |
| char buf[32]; |
| |
| tep_strerror(tep, ret, buf, 32) |
| printf("Failed to register handler for hrtimer_expire_entry: %s\n", buf); |
| } else { |
| switch (ret) { |
| case TEP_REGISTER_SUCCESS: |
| printf ("Registered handler for hrtimer_expire_entry\n"); |
| break; |
| case TEP_REGISTER_SUCCESS_OVERWRITE: |
| printf ("Overwrote handler for hrtimer_expire_entry\n"); |
| break; |
| } |
| } |
| ... |
| ret = tep_unregister_event_handler(tep, -1, "timer", "hrtimer_expire_entry", |
| timer_expire_handler, NULL); |
| if ( ret ) |
| printf ("Failed to unregister handler for hrtimer_expire_entry\n"); |
| |
| -- |
| |
| FILES |
| ----- |
| [verse] |
| -- |
| *event-parse.h* |
| Header file to include in order to have access to the library APIs. |
| *trace-seq.h* |
| Header file to include in order to have access to trace sequences |
| related APIs. Trace sequences are used to allow a function to call |
| several other functions to create a string of data to use. |
| *-ltraceevent* |
| Linker switch to add when building a program that uses the library. |
| -- |
| |
| SEE ALSO |
| -------- |
| _libtraceevent(3)_, _trace-cmd(1)_ |
| |
| AUTHOR |
| ------ |
| [verse] |
| -- |
| *Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*. |
| *Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page. |
| -- |
| REPORTING BUGS |
| -------------- |
| Report bugs to <linux-trace-devel@vger.kernel.org> |
| |
| LICENSE |
| ------- |
| libtraceevent is Free Software licensed under the GNU LGPL 2.1 |
| |
| RESOURCES |
| --------- |
| https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git |
