tools lib traceevent: Man pages for event handler APIs
Create man pages for libtraceevent APIs: tep_register_event_handler() tep_unregister_event_handler() Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: linux-trace-devel@vger.kernel.org Link: http://lore.kernel.org/linux-trace-devel/20190503091119.23399-11-tstoyanov@vmware.com Link: http://lkml.kernel.org/r/20190510200107.536391771@goodmis.org Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Tzvetomir Stoyanov
Arnaldo Carvalho de Melo
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c127ef5676
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libtraceevent(3)
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================
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NAME
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----
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tep_register_event_handler, tep_unregister_event_handler - Register /
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unregisters a callback function to parse an event information.
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SYNOPSIS
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--------
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[verse]
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--
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*#include <event-parse.h>*
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enum *tep_reg_handler* {
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_TEP_REGISTER_SUCCESS_,
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_TEP_REGISTER_SUCCESS_OVERWRITE_,
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};
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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_);
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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_);
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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);
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--
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DESCRIPTION
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-----------
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The _tep_register_event_handler()_ function registers a handler function,
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which is going to be called to parse the information for a given event.
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The _tep_ argument is the trace event parser context. The _id_ argument is
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the id of the event. The _sys_name_ argument is the name of the system,
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the event belongs to. The _event_name_ argument is the name of the event.
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If _id_ is >= 0, it is used to find the event, otherwise _sys_name_ and
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_event_name_ are used. The _func_ is a pointer to the function, which is going
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to be called to parse the event information. The _context_ argument is a pointer
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to the context data, which will be passed to the _func_. If a handler function
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for the same event is already registered, it will be overridden with the new
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one. This mechanism allows a developer to override the parsing of a given event.
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If for some reason the default print format is not sufficient, the developer
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can register a function for an event to be used to parse the data instead.
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The _tep_unregister_event_handler()_ function unregisters the handler function,
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previously registered with _tep_register_event_handler()_. The _tep_ argument
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is the trace event parser context. The _id_, _sys_name_, _event_name_, _func_,
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and _context_ are the same arguments, as when the callback function _func_ was
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registered.
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The _tep_event_handler_func_ is the type of the custom event handler
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function. The _s_ argument is the trace sequence, it can be used to create a
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custom string, describing the event. A _record_ to get the event from is passed
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as input parameter and also the _event_ - the handle to the record's event. The
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_context_ is custom context, set when the custom event handler is registered.
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RETURN VALUE
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------------
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The _tep_register_event_handler()_ function returns _TEP_REGISTER_SUCCESS_
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if the new handler is registered successfully or
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_TEP_REGISTER_SUCCESS_OVERWRITE_ if an existing handler is overwritten.
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If there is not enough memory to complete the registration,
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TEP_ERRNO__MEM_ALLOC_FAILED is returned.
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The _tep_unregister_event_handler()_ function returns 0 if _func_ was removed
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successful or, -1 if the event was not found.
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The _tep_event_handler_func_ should return -1 in case of an error,
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or 0 otherwise.
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EXAMPLE
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-------
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[source,c]
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--
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#include <event-parse.h>
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#include <trace-seq.h>
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...
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struct tep_handle *tep = tep_alloc();
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...
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int timer_expire_handler(struct trace_seq *s, struct tep_record *record,
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struct tep_event *event, void *context)
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{
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trace_seq_printf(s, "hrtimer=");
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if (tep_print_num_field(s, "0x%llx", event, "timer", record, 0) == -1)
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tep_print_num_field(s, "0x%llx", event, "hrtimer", record, 1);
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trace_seq_printf(s, " now=");
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tep_print_num_field(s, "%llu", event, "now", record, 1);
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tep_print_func_field(s, " function=%s", event, "function", record, 0);
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return 0;
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}
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...
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int ret;
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ret = tep_register_event_handler(tep, -1, "timer", "hrtimer_expire_entry",
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timer_expire_handler, NULL);
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if (ret < 0) {
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char buf[32];
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tep_strerror(tep, ret, buf, 32)
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printf("Failed to register handler for hrtimer_expire_entry: %s\n", buf);
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} else {
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switch (ret) {
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case TEP_REGISTER_SUCCESS:
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printf ("Registered handler for hrtimer_expire_entry\n");
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break;
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case TEP_REGISTER_SUCCESS_OVERWRITE:
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printf ("Overwrote handler for hrtimer_expire_entry\n");
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break;
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}
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}
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...
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ret = tep_unregister_event_handler(tep, -1, "timer", "hrtimer_expire_entry",
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timer_expire_handler, NULL);
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if ( ret )
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printf ("Failed to unregister handler for hrtimer_expire_entry\n");
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--
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FILES
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-----
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[verse]
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--
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*event-parse.h*
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Header file to include in order to have access to the library APIs.
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*trace-seq.h*
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Header file to include in order to have access to trace sequences
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related APIs. Trace sequences are used to allow a function to call
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several other functions to create a string of data to use.
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*-ltraceevent*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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_libtraceevent(3)_, _trace-cmd(1)_
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtraceevent is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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