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Diffstat (limited to 'Documentation/libtraceevent-reg_event_handler.txt')
| -rw-r--r-- | Documentation/libtraceevent-reg_event_handler.txt | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/Documentation/libtraceevent-reg_event_handler.txt b/Documentation/libtraceevent-reg_event_handler.txt new file mode 100644 index 0000000..90ab7f0 --- /dev/null +++ b/Documentation/libtraceevent-reg_event_handler.txt @@ -0,0 +1,156 @@ +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/libs/libtrace/libtraceevent.git/ |