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    Subject[tip:perf/core] tools lib traceevent: Man pages for event handler APIs
    Commit-ID:  db5570e5e30aa2362fc34f5ee3b4b741362d41fa
    Gitweb: https://git.kernel.org/tip/db5570e5e30aa2362fc34f5ee3b4b741362d41fa
    Author: Tzvetomir Stoyanov <tstoyanov@vmware.com>
    AuthorDate: Fri, 10 May 2019 15:56:17 -0400
    Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
    CommitDate: Wed, 15 May 2019 16:36:48 -0300

    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>
    ---
    .../libtraceevent-reg_event_handler.txt | 156 +++++++++++++++++++++
    1 file changed, 156 insertions(+)

    diff --git a/tools/lib/traceevent/Documentation/libtraceevent-reg_event_handler.txt b/tools/lib/traceevent/Documentation/libtraceevent-reg_event_handler.txt
    new file mode 100644
    index 000000000000..53d37d72a1c1
    --- /dev/null
    +++ b/tools/lib/traceevent/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/linux/kernel/git/torvalds/linux.git
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