libperf: Initial documentation

Add initial drafts of documentation files, hugely unfinished.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190721112506.12306-80-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/lib/Documentation/Makefile

+all:
+	rst2man man/libperf.rst > man/libperf.7
+	rst2pdf tutorial/tutorial.rst
+
+clean:
+	rm -f man/libperf.7
+	rm -f tutorial/tutorial.pdf

tools/perf/lib/Documentation/man/libperf.rst

+.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+libperf
+
+The libperf library provides an API to access the linux kernel perf
+events subsystem. It provides the following high level objects:
+
+  - struct perf_cpu_map
+  - struct perf_thread_map
+  - struct perf_evlist
+  - struct perf_evsel
+
+reference
+=========
+Function reference by header files:
+
+perf/core.h
+-----------
+.. code-block:: c
+
+  typedef int (\*libperf_print_fn_t)(enum libperf_print_level level,
+                                     const char \*, va_list ap);
+
+  void libperf_set_print(libperf_print_fn_t fn);
+
+perf/cpumap.h
+-------------
+.. code-block:: c
+
+  struct perf_cpu_map \*perf_cpu_map__dummy_new(void);
+  struct perf_cpu_map \*perf_cpu_map__new(const char \*cpu_list);
+  struct perf_cpu_map \*perf_cpu_map__read(FILE \*file);
+  struct perf_cpu_map \*perf_cpu_map__get(struct perf_cpu_map \*map);
+  void perf_cpu_map__put(struct perf_cpu_map \*map);
+  int perf_cpu_map__cpu(const struct perf_cpu_map \*cpus, int idx);
+  int perf_cpu_map__nr(const struct perf_cpu_map \*cpus);
+  perf_cpu_map__for_each_cpu(cpu, idx, cpus)
+
+perf/threadmap.h
+----------------
+.. code-block:: c
+
+  struct perf_thread_map \*perf_thread_map__new_dummy(void);
+  void perf_thread_map__set_pid(struct perf_thread_map \*map, int thread, pid_t pid);
+  char \*perf_thread_map__comm(struct perf_thread_map \*map, int thread);
+  struct perf_thread_map \*perf_thread_map__get(struct perf_thread_map \*map);
+  void perf_thread_map__put(struct perf_thread_map \*map);
+
+perf/evlist.h
+-------------
+.. code-block::
+
+  void perf_evlist__init(struct perf_evlist \*evlist);
+  void perf_evlist__add(struct perf_evlist \*evlist,
+                      struct perf_evsel \*evsel);
+  void perf_evlist__remove(struct perf_evlist \*evlist,
+                         struct perf_evsel \*evsel);
+  struct perf_evlist \*perf_evlist__new(void);
+  void perf_evlist__delete(struct perf_evlist \*evlist);
+  struct perf_evsel\* perf_evlist__next(struct perf_evlist \*evlist,
+                                     struct perf_evsel \*evsel);
+  int perf_evlist__open(struct perf_evlist \*evlist);
+  void perf_evlist__close(struct perf_evlist \*evlist);
+  void perf_evlist__enable(struct perf_evlist \*evlist);
+  void perf_evlist__disable(struct perf_evlist \*evlist);
+  perf_evlist__for_each_evsel(evlist, pos)
+  void perf_evlist__set_maps(struct perf_evlist \*evlist,
+                           struct perf_cpu_map \*cpus,
+                           struct perf_thread_map \*threads);
+
+perf/evsel.h
+------------
+.. code-block:: c
+
+  struct perf_counts_values {
+        union {
+                struct {
+                        uint64_t val;
+                        uint64_t ena;
+                        uint64_t run;
+                };
+                uint64_t values[3];
+        };
+  };
+
+  void perf_evsel__init(struct perf_evsel \*evsel,
+                      struct perf_event_attr \*attr);
+  struct perf_evsel \*perf_evsel__new(struct perf_event_attr \*attr);
+  void perf_evsel__delete(struct perf_evsel \*evsel);
+  int perf_evsel__open(struct perf_evsel \*evsel, struct perf_cpu_map \*cpus,
+                     struct perf_thread_map \*threads);
+  void perf_evsel__close(struct perf_evsel \*evsel);
+  int perf_evsel__read(struct perf_evsel \*evsel, int cpu, int thread,
+                     struct perf_counts_values \*count);
+  int perf_evsel__enable(struct perf_evsel \*evsel);
+  int perf_evsel__disable(struct perf_evsel \*evsel);
+  int perf_evsel__apply_filter(struct perf_evsel \*evsel, const char \*filter);
+  struct perf_cpu_map \*perf_evsel__cpus(struct perf_evsel \*evsel);
+  struct perf_thread_map \*perf_evsel__threads(struct perf_evsel \*evsel);
+  struct perf_event_attr \*perf_evsel__attr(struct perf_evsel \*evsel);

tools/perf/lib/Documentation/tutorial/tutorial.rst

+.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+libperf tutorial
+================
+
+Compile and install libperf from kernel sources
+===============================================
+.. code-block:: bash
+
+  git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
+  cd linux/tools/perf/lib
+  make
+  sudo make install prefix=/usr
+
+Libperf object
+==============
+The libperf library provides several high level objects:
+
+struct perf_cpu_map
+  Provides a cpu list abstraction.
+
+struct perf_thread_map
+  Provides a thread list abstraction.
+
+struct perf_evsel
+  Provides an abstraction for single a perf event.
+
+struct perf_evlist
+  Gathers several struct perf_evsel object and performs functions on all of them.
+
+The exported API binds these objects together,
+for full reference see the libperf.7 man page.
+
+Examples
+========
+Examples aim to explain libperf functionality on simple use cases.
+They are based in on a checked out linux kernel git tree:
+
+.. code-block:: bash
+
+  $ cd tools/perf/lib/Documentation/tutorial/
+  $ ls -d  ex-*
+  ex-1-compile  ex-2-evsel-stat  ex-3-evlist-stat
+
+ex-1-compile example
+====================
+This example shows the basic usage of *struct perf_cpu_map*,
+how to create it and display its cpus:
+
+.. code-block:: bash
+
+  $ cd ex-1-compile/
+  $ make
+  gcc -o test test.c -lperf
+  $ ./test
+  0 1 2 3 4 5 6 7
+
+
+The full code listing is here:
+
+.. code-block:: c
+
+   1 #include <perf/cpumap.h>
+   2
+   3 int main(int argc, char **Argv)
+   4 {
+   5         struct perf_cpu_map *cpus;
+   6         int cpu, tmp;
+   7
+   8         cpus = perf_cpu_map__new(NULL);
+   9
+  10         perf_cpu_map__for_each_cpu(cpu, tmp, cpus)
+  11                 fprintf(stdout, "%d ", cpu);
+  12
+  13         fprintf(stdout, "\n");
+  14
+  15         perf_cpu_map__put(cpus);
+  16         return 0;
+  17 }
+
+
+First you need to include the proper header to have *struct perf_cpumap*
+declaration and functions:
+
+.. code-block:: c
+
+   1 #include <perf/cpumap.h>
+
+
+The *struct perf_cpumap* object is created by *perf_cpu_map__new* call.
+The *NULL* argument asks it to populate the object with the current online CPUs list:
+
+.. code-block:: c
+
+   8         cpus = perf_cpu_map__new(NULL);
+
+This is paired with a *perf_cpu_map__put*, that drops its reference at the end, possibly deleting it.
+
+.. code-block:: c
+
+  15         perf_cpu_map__put(cpus);
+
+The iteration through the *struct perf_cpumap* CPUs is done using the *perf_cpu_map__for_each_cpu*
+macro which requires 3 arguments:
+
+- cpu  - the cpu numer
+- tmp  - iteration helper variable
+- cpus - the *struct perf_cpumap* object
+
+.. code-block:: c
+
+  10         perf_cpu_map__for_each_cpu(cpu, tmp, cpus)
+  11                 fprintf(stdout, "%d ", cpu);
+
+ex-2-evsel-stat example
+=======================
+
+TBD
+
+ex-3-evlist-stat example
+========================
+
+TBD