NAME

       tracefs_options_get_supported, tracefs_option_is_supported, tracefs_options_get_enabled,
       tracefs_option_is_enabled, tracefs_option_mask_is_set, tracefs_option_id - Get and check
       ftrace options.

SYNOPSIS

       #include <tracefs.h>

       const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
       bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
       const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
       bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
       bool tracefs_option_mask_is_set(const struct tracefs_options_mask options, enum tracefs_option_id id);
       enum tracefs_option_id *tracefs_option_id(const char *name);

DESCRIPTION

       This set of APIs can be used to get and check current ftrace options. Supported ftrace
       options may depend on the kernel version and the kernel configuration.

       The tracefs_options_get_supported() function gets all ftrace options supported by the
       system in the given instance. If instance is NULL, supported options of the top trace
       instance are returned. The set of supported options is the same in all created trace
       instances, but may be different than the top trace instance.

       The *tracefs_option_is_supported()/ function checks if the option with given id is
       supported by the system in the given instance. If instance is NULL, the top trace instance
       is used. If an option is supported at the top trace instance, it it may not be supported
       in a created trace instance.

       The tracefs_options_get_enabled() function gets all ftrace options, currently enabled in
       the given instance. If instance is NULL, enabled options of the top trace instance are
       returned.

       The tracefs_option_is_enabled() function checks if the option with given id is enabled in
       the given instance. If instance is NULL, the top trace instance is used.

       The tracefs_option_mask_is_set() function checks if the bit, corresponding to the option
       with id is set in the options bitmask returned from tracefs_option_get_enabled() and
       tracefs_option_is_supported().

       The tracefs_option_id() converts an option name into its corresponding id, if it is found.
       This allows to find the option id to use in the other functions if only the name is known.

RETURN VALUE

       The tracefs_options_get_supported() and tracefs_options_get_enabled() functions, on
       success, return a pointer to the bitmask within the instance, or a global bitmask for the
       top level, or NULL in case of an error. As the returned bitmask is part of the instance
       structure (or a global variable) and must not be freed or modified.

       The tracefs_option_is_supported() and tracefs_option_is_enabled() functions return true if
       the option in supported / enabled, or false otherwise.

       The tracefs_option_mask_is_set() returns true if the corresponding option is set in the
       mask or false otherwise.

       The tracefs_option_id() returns the corresponding id defined by tracefs_options(3) from
       the given name. If the name can not be found, then TRACEFS_OPTION_INVALID is returned.

EXAMPLE

           #include <tracefs.h>
           ...
           const struct tracefs_options_mask *options;
           ...
           options = tracefs_options_get_supported(NULL);
           if (!options) {
                   /* Failed to get supported options */
           } else {
                   ...
           }
           ...
           options = tracefs_options_get_enabled(NULL);
           if (!options) {
                   /* Failed to get options, enabled in the top instance */
           } else {
                   ...
           }
           if (tracefs_options_mask_is_set(options, TRACEFS_OPTION_LATENCY_FORMAT)) {
                   ...
           }
           ...

           if (tracefs_option_is_supported(NULL, TRACEFS_OPTION_LATENCY_FORMAT)) {
                   /* Latency format option is supprted */
           }

           ...

           if (tracefs_option_is_enabled(NULL, TRACEFS_OPTION_STACKTRACE)) {
                   /* Stacktrace option is enabled in the top instance */
           }

FILES

           tracefs.h
                   Header file to include in order to have access to the library APIs.
           -ltracefs
                   Linker switch to add when building a program that uses the library.

SEE ALSO

       libtracefs(3), libtraceevent(3), trace-cmd(1)

AUTHOR

           Steven Rostedt <rostedt@goodmis.org[1]>
           Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>

REPORTING BUGS

       Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE

       libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES

       https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING

       Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of
       the GNU Public License (GPL).

NOTES

        1. rostedt@goodmis.org
           mailto:rostedt@goodmis.org

        2. tz.stoyanov@gmail.com
           mailto:tz.stoyanov@gmail.com

        3. linux-trace-devel@vger.kernel.org
           mailto:linux-trace-devel@vger.kernel.org