[PATCH v5 5/6] perf config: Add 'set' feature

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

This patch consists of functions
which can set specific config variables.
For the syntax examples,

   perf config [options] [section.name[=value] ...]

   set specific config variables
   # perf config report.queue-size=100M report.children=true

Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
---
 tools/perf/Documentation/perf-config.txt |  2 +-
 tools/perf/builtin-config.c              | 55 +++++++++++++++++++++++++++++---
 tools/perf/util/cache.h                  |  3 +-
 tools/perf/util/config.c                 | 27 ++++++++++++++++
 4 files changed, 80 insertions(+), 7 deletions(-)

diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index 691d52b..9c95af8 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -8,7 +8,7 @@ perf-config - Get and set variables in a configuration file.
 SYNOPSIS
 --------
 [verse]
-'perf config' [<file-option>] [section.name ...]
+'perf config' [<file-option>] [section.name[=value] ...]
 or
 'perf config' [<file-option>] -l | --list
 or
diff --git a/tools/perf/builtin-config.c b/tools/perf/builtin-config.c
index 0f2193a..d5cc3e8 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 *config_file_name;
 
 static const char * const config_usage[] = {
-	"perf config [options] [section.name ...]",
+	"perf config [options] [section.name[=value] ...]",
 	NULL
 };
 
@@ -412,7 +412,8 @@ static void find_config(struct config_section **section_node,
 		*element_node = NULL;
 }
 
-static int show_spec_config(const char *section_name, const char *name)
+static int show_spec_config(const char *section_name, const char *name,
+			    char *value __maybe_unused)
 {
 	int i;
 	struct config_section *section_node = NULL;
@@ -488,6 +489,34 @@ static char *normalize_value(const char *section_name, const char *name, const c
 	return normalized;
 }
 
+static int set_config(const char *section_name, const char *name, char *value)
+{
+	struct config_section *section_node = NULL;
+	struct config_element *element_node = NULL;
+
+	find_config(&section_node, &element_node, section_name, name);
+	if (value != NULL) {
+		value = normalize_value(section_name, name, value);
+
+		/* if there isn't existent section, add a new section */
+		if (!section_node) {
+			section_node = init_section(section_name);
+			if (!section_node)
+				return -1;
+			list_add_tail(&section_node->list, &sections);
+		}
+		/* if nothing to replace, add a new element which contains key-value pair. */
+		if (!element_node) {
+			add_element(&section_node->element_head, name, value);
+		} else {
+			free(element_node->value);
+			element_node->value = value;
+		}
+	}
+
+	return perf_configset_write_in_full(config_file_name);
+}
+
 static int collect_current_config(const char *var, const char *value,
 			  void *cb __maybe_unused)
 {
@@ -557,7 +586,7 @@ static int show_all_config(void)
 	return 0;
 }
 
-static int perf_configset_with_option(configset_fn_t fn, const char *var)
+static int perf_configset_with_option(configset_fn_t fn, const char *var, char *value)
 {
 	char *section_name;
 	char *name;
@@ -585,8 +614,18 @@ static int perf_configset_with_option(configset_fn_t fn, const char *var)
 	section_name = strsep(&key, ".");
 	name = strsep(&key, ".");
 	free(key);
+	if (!value) {
+		/* do nothing */
+	} else if (!strcmp(value, "=")) {
+		pr_err("The config variable does not contain a value: %s.%s\n",
+		       section_name, name);
+		return -1;
+	} else {
+		value++;
+		name = strsep(&name, "=");
+	}
 
-	return fn(section_name, name);
+	return fn(section_name, name, value);
 
 	pr_err("invalid key: %s\n", var);
 	return -1;
@@ -625,7 +664,13 @@ int cmd_config(int argc, const char **argv, const char *prefix __maybe_unused)
 	default:
 		if (argc) {
 			for (i = 0; argv[i]; i++) {
-				ret = perf_configset_with_option(show_spec_config, argv[i]);
+				char *value = strchr(argv[i], '=');
+				if (value == NULL)
+					ret = perf_configset_with_option(show_spec_config,
+									 argv[i], value);
+				else
+					ret = perf_configset_with_option(set_config,
+									 argv[i], value);
 				if (ret < 0)
 					break;
 			}
diff --git a/tools/perf/util/cache.h b/tools/perf/util/cache.h
index 6fe734c..0b68c89 100644
--- a/tools/perf/util/cache.h
+++ b/tools/perf/util/cache.h
@@ -34,7 +34,8 @@ struct config_section {
 
 struct list_head sections;
 
-typedef int (*configset_fn_t)(const char *, const char *);
+extern int perf_configset_write_in_full(const char *file_name);
+typedef int (*configset_fn_t)(const char *, const char *, char*);
 typedef int (*config_fn_t)(const char *, const char *, void *);
 extern int perf_default_config(const char *, const char *, void *);
 extern int perf_config(config_fn_t fn, void *);
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 23fa8c5..4c13991 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -506,6 +506,33 @@ out:
 	return ret;
 }
 
+int perf_configset_write_in_full(const char *file_name)
+{
+	struct config_section *section_node;
+	struct config_element *element_node;
+	const char *first_line = "# this file is auto-generated.";
+	FILE *fp = fopen(file_name, "w");
+
+	if (!fp) {
+		pr_err("Error: %s: Can't open this file\n", file_name);
+		return -1;
+	}
+
+	fprintf(fp, "%s\n", first_line);
+	/* overwrite configvariables */
+	list_for_each_entry(section_node, &sections, list) {
+		fprintf(fp, "[%s]\n", section_node->name);
+		list_for_each_entry(element_node, &section_node->element_head, list) {
+			if (element_node->value)
+				fprintf(fp, "\t%s = %s\n",
+					element_node->name, element_node->value);
+		}
+	}
+	fclose(fp);
+
+	return 0;
+}
+
 /*
  * Call this to report error for your variable that should not
  * get a boolean value (i.e. "[my] var" means "true").
-- 
1.9.1