perf report: Improve sort key recognition

 - allow case-insensitive tokens - such as --sort Comm,Symbol
 - allow substring shortcuts: --sort sym
 - detect invalid tokens and bail out

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/perf_counter/builtin-report.c

@@ -453,28 +453,18 @@ static int sort_dimension__add(char *tok)
 		if (sd->taken)
 			continue;
 
-		if (strcmp(tok, sd->name))
+		if (strncasecmp(tok, sd->name, strlen(tok)))
 			continue;
 
 		list_add_tail(&sd->entry->list, &hist_entry__sort_list);
 		sd->taken = 1;
+
 		return 0;
 	}
 
 	return -ESRCH;
 }
 
-static void setup_sorting(void)
-{
-	char *tmp, *tok, *str = strdup(sort_order);
-
-	for (tok = strtok_r(str, ", ", &tmp);
-			tok; tok = strtok_r(NULL, ", ", &tmp))
-		sort_dimension__add(tok);
-
-	free(str);
-}
-
 static int64_t
 hist_entry__cmp(struct hist_entry *left, struct hist_entry *right)
 {
@@ -880,6 +870,21 @@ static const struct option options[] = {
 	OPT_END()
 };
 
+static void setup_sorting(void)
+{
+	char *tmp, *tok, *str = strdup(sort_order);
+
+	for (tok = strtok_r(str, ", ", &tmp);
+			tok; tok = strtok_r(NULL, ", ", &tmp)) {
+		if (sort_dimension__add(tok) < 0) {
+			error("Unknown --sort key: `%s'", tok);
+			usage_with_options(report_usage, options);
+		}
+	}
+
+	free(str);
+}
+
 int cmd_report(int argc, const char **argv, const char *prefix)
 {
 	symbol__init();