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

[Taeung Song <treeze.taeung@gmail.com>]

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 <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Taeung Song <treeze.taeung@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