perf_counter tools: Add new OPT_CALLBACK_DEFAULT option

There is no predefined macro to create an option that can have
a custom value or a default one if none is given.

This patch provides a new helper OPT_CALLBACK_DEFAULT() which
defines such kind of option.

For example, considering an option -c, we want to get the
default value in the following cases:

    perf command -c -d
    perf command -d -c

And the foo value when it's given:

    perf command -c foo -d
    perf command -d -c foo

That's also why PARSE_OPT_LASTARG_DEFAULT is extended here to
support default values whatever the position of the option, not
only in the end.

Should it now be renamed to PARSE_OPT_ARG_DEFAULT ?

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: git@vger.kernel.org
LKML-Reference: <1246550301-8954-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/parse-options.c

@@ -20,7 +20,8 @@ static int get_arg(struct parse_opt_ctx_t *p, const struct option *opt,
 	if (p->opt) {
 		*arg = p->opt;
 		p->opt = NULL;
-	} else if (p->argc == 1 && (opt->flags & PARSE_OPT_LASTARG_DEFAULT)) {
+	} else if ((opt->flags & PARSE_OPT_LASTARG_DEFAULT) && (p->argc == 1 ||
+		    **(p->argv + 1) == '-')) {
 		*arg = (const char *)opt->defval;
 	} else if (p->argc > 1) {
 		p->argc--;

tools/perf/util/parse-options.h

@@ -104,6 +104,8 @@ struct option {
 	{ .type = OPTION_CALLBACK, .short_name = (s), .long_name = (l), .value = (v), .argh = "time", .help = (h), .callback = parse_opt_approxidate_cb }
 #define OPT_CALLBACK(s, l, v, a, h, f) \
 	{ .type = OPTION_CALLBACK, .short_name = (s), .long_name = (l), .value = (v), (a), .help = (h), .callback = (f) }
+#define OPT_CALLBACK_DEFAULT(s, l, v, a, h, f, d) \
+	{ .type = OPTION_CALLBACK, .short_name = (s), .long_name = (l), .value = (v), (a), .help = (h), .callback = (f), .defval = (intptr_t)d, .flags = PARSE_OPT_LASTARG_DEFAULT }
 
 /* parse_options() will filter out the processed options and leave the
  * non-option argments in argv[].