[PATCH v2 5/7] perf config: Add support for write functionality

[Taeung Song]

Add support for write functionality in config file
(i.e. user or system config file).
This functionality autogerates a config file with
existing config key-value pairs.

For the syntax examples,

    perf config [<file-option>] [section.name[=value] ...]

e.g. You can set the ui.show-headers to false with

    # perf config ui.show-headers=false

If you want to add or modify several config items, you can do like

    # perf config annotate.show_nr_jumps=false kmem.default=slab

Sure, you can also use file-option --user or --system.

Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Jiri Olsa <jo...@kernel.org>
Cc: Wang Nan <wangn...@huawei.com>
Signed-off-by: Taeung Song <treeze.tae...@gmail.com>
---
 tools/perf/builtin-config.c | 40 +++++++++++++++++++++++++++++++++++++++-
 tools/perf/util/config.c    |  6 ++++++
 tools/perf/util/config.h    |  2 ++
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-config.c b/tools/perf/builtin-config.c
index 098d2df..2e7e295 100644
--- a/tools/perf/builtin-config.c
+++ b/tools/perf/builtin-config.c
@@ -17,7 +17,7 @@
 static bool use_system_config, use_user_config;
 
 static const char * const config_usage[] = {
-       "perf config [<file-option>] [options] [section.name ...]",
+       "perf config [<file-option>] [options] [section.name[=value] ...]",
        NULL
 };
 
@@ -33,6 +33,37 @@ static struct option config_options[] = {
        OPT_END()
 };
 
+static int set_config(struct perf_config_set *set, const char *file_name,
+                     const char *var, const char *value)
+{
+       struct perf_config_section *section = NULL;
+       struct perf_config_item *item = NULL;
+       const char *first_line = "# this file is auto-generated.";
+       FILE *fp = fopen(file_name, "w");
+
+       if (!fp)
+               return -1;
+       if (set == NULL)
+               return -1;
+
+       perf_config_set__collect(set, var, value);
+       fprintf(fp, "%s\n", first_line);
+
+       /* overwrite configvariables */
+       perf_config_items__for_each_entry(&set->sections, section) {
+               fprintf(fp, "[%s]\n", section->name);
+
+               perf_config_items__for_each_entry(&section->items, item) {
+                       if (item->value)
+                               fprintf(fp, "\t%s = %s\n",
+                                       item->name, item->value);
+               }
+       }
+       fclose(fp);
+
+       return 0;
+}
+
 static int show_spec_config(struct perf_config_set *set, const char *var)
 {
        struct perf_config_section *section;
@@ -205,6 +236,13 @@ int cmd_config(int argc, const char **argv, const char 
*prefix __maybe_unused)
                                break;
                        if (value == NULL)
                                ret = show_spec_config(set, var);
+                       else {
+                               const char *config_filename = 
config_exclusive_filename;
+
+                               if (!config_exclusive_filename)
+                                       config_filename = user_config;
+                               ret = set_config(set, config_filename, var, 
value);
+                       }
                        free(var);
                        free(value);
                }
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 18dae74..c8fb65d 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -602,6 +602,12 @@ static int collect_config(const char *var, const char 
*value,
        return -1;
 }
 
+int perf_config_set__collect(struct perf_config_set *set,
+                            const char *var, const char *value)
+{
+       return collect_config(var, value, set);
+}
+
 static int perf_config_set__init(struct perf_config_set *set)
 {
        int ret = -1;
diff --git a/tools/perf/util/config.h b/tools/perf/util/config.h
index 6f813d4..0fcdb8c 100644
--- a/tools/perf/util/config.h
+++ b/tools/perf/util/config.h
@@ -33,6 +33,8 @@ const char *perf_etc_perfconfig(void);
 
 struct perf_config_set *perf_config_set__new(void);
 void perf_config_set__delete(struct perf_config_set *set);
+int perf_config_set__collect(struct perf_config_set *set,
+                            const char *var, const char *value);
 void perf_config__init(void);
 void perf_config__exit(void);
 void perf_config__refresh(void);
-- 
2.7.4