lib/cmdline: Allow get_options() to take 0 to validate the input

Allow get_options() to take 0 as a number of integers parameter to validate
the input.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

lib/cmdline.c

@@ -91,6 +91,9 @@ EXPORT_SYMBOL(get_option);
  *	full, or when no more numbers can be retrieved from the
  *	string.
  *
+ *	When @nints is 0, the function just validates the given @str and
+ *	returns the amount of parseable integers as described below.
+ *
  *	Returns:
  *
  *	The first element is filled by the number of collected integers
@@ -103,15 +106,20 @@ EXPORT_SYMBOL(get_option);
 
 char *get_options(const char *str, int nints, int *ints)
 {
+	bool validate = (nints == 0);
 	int res, i = 1;
 
-	while (i < nints) {
-		res = get_option((char **)&str, ints + i);
+	while (i < nints || validate) {
+		int *pint = validate ? ints : ints + i;
+
+		res = get_option((char **)&str, pint);
 		if (res == 0)
 			break;
 		if (res == 3) {
+			int n = validate ? 0 : nints - i;
 			int range_nums;
-			range_nums = get_range((char **)&str, ints + i, nints - i);
+
+			range_nums = get_range((char **)&str, pint, n);
 			if (range_nums < 0)
 				break;
 			/*

lib/cmdline_kunit.c

@@ -109,13 +109,22 @@ static void cmdline_do_one_range_test(struct kunit *test, const char *in,
 {
 	unsigned int i;
 	int r[16];
+	int *p;
 
 	memset(r, 0, sizeof(r));
 	get_options(in, ARRAY_SIZE(r), r);
-	KUNIT_EXPECT_EQ_MSG(test, r[0], e[0], "in test %u expected %d numbers, got %d",
+	KUNIT_EXPECT_EQ_MSG(test, r[0], e[0], "in test %u (parsed) expected %d numbers, got %d",
 			    n, e[0], r[0]);
 	for (i = 1; i < ARRAY_SIZE(r); i++)
 		KUNIT_EXPECT_EQ_MSG(test, r[i], e[i], "in test %u at %u", n, i);
+
+	memset(r, 0, sizeof(r));
+	get_options(in, 0, r);
+	KUNIT_EXPECT_EQ_MSG(test, r[0], e[0], "in test %u (validated) expected %d numbers, got %d",
+			    n, e[0], r[0]);
+
+	p = memchr_inv(&r[1], 0, sizeof(r) - sizeof(r[0]));
+	KUNIT_EXPECT_PTR_EQ_MSG(test, p, (int *)0, "in test %u at %u out of bound", n, p - r);
 }
 
 static void cmdline_test_range(struct kunit *test)