[PATCH v3] selftests: rtc: Support harness test filtering and arguments

[Wake Liu <wakel@google.com>]

rtctest implements its own main() function with a rigid switch (argc)
check that only accepts an optional single argument for the RTC device
node path. This prevents kselftest_harness standard arguments from
working properly:

1. Passing filter options like -t <name> or -T <name> triggers a usage
   error because argc is greater than 2.
2. Passing -l or -h causes rtctest to treat "-l" or "-h" as the device
   node path and fail with access() errors before ever reaching the
   harness argument checker.

Parse command line arguments with getopt() to pass all kselftest harness
options (such as -t, -T, -v, -V, -f, -F, -r, -d, -h, and -l) through to
test_harness_run(), while preserving the ability to specify an optional
RTC device node path as a non-option argument. Only reset optind once
all options have been parsed, so the harness re-parses them from a clean
getopt() state, and bypass device accessibility checks when help or test
listing is requested.

Signed-off-by: Wake Liu <wakel@google.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
v3:
- Don't call test_harness_run() from inside the getopt() loop for -h
  and -l. getopt() keeps its position inside grouped options, so with
  e.g. "-ld" the harness resumed at 'd', missed -l/-h and ran the whole
  suite without the device check. Record -h/-l instead and reset optind
  only after all options have been parsed. Reported by Sashiko AI
  review.
- Kept Alexandre's Acked-by as the change is limited to the -h/-l
  handling. Alexandre, please let me know if you'd rather re-check.

v2: https://lore.kernel.org/all/20261105030834.3318480-1-wakel@google.com/
- Rebased onto v7.4-rc1, no code changes.
- Added Alexandre's Acked-by.

v1: https://lore.kernel.org/all/20260910034821.2935214-1-wakel@google.com/

Alexandre, if you're still fine with it, could you queue this via the
RTC tree along with the other rtctest changes? Shuah, please let me know
if you would rather take it via kselftest.

 tools/testing/selftests/rtc/rtctest.c | 54 ++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/rtc/rtctest.c b/tools/testing/selftests/rtc/rtctest.c
index 552191fe1ca0..21c37764f9d3 100644
--- a/tools/testing/selftests/rtc/rtctest.c
+++ b/tools/testing/selftests/rtc/rtctest.c
@@ -487,18 +487,54 @@ TEST_F_TIMEOUT(rtc, alarm_wkalm_set_minute, 65) {
 int main(int argc, char **argv)
 {
 	int ret = -1;
+	int opt, i;
+	int non_opt = 0;
+	bool skip_dev_check = false;
+
+	while ((opt = getopt(argc, argv, "dhlF:f:V:v:t:T:r:")) != -1) {
+		switch (opt) {
+		case 'h':
+			fprintf(stderr,
+				"Usage: %s [-h|-l|-d] [-t|-T|-v|-V|-f|-F|-r name] [rtcdev]\n\n",
+				argv[0]);
+			skip_dev_check = true;
+			break;
+		case 'l':
+			skip_dev_check = true;
+			break;
+		case '?':
+			fprintf(stderr,
+				"Usage: %s [-h|-l|-d] [-t|-T|-v|-V|-f|-F|-r name] [rtcdev]\n",
+				argv[0]);
+			return KSFT_FAIL;
+		default:
+			break;
+		}
+	}
 
-	switch (argc) {
-	case 2:
-		rtc_file = argv[1];
-		/* FALLTHROUGH */
-	case 1:
-		break;
-	default:
-		fprintf(stderr, "usage: %s [rtcdev]\n", argv[0]);
-		return 1;
+	for (i = optind; i < argc; i++) {
+		if (non_opt == 0) {
+			rtc_file = argv[i];
+			non_opt++;
+		} else {
+			fprintf(stderr,
+				"Usage: %s [-h|-l|-d] [-t|-T|-v|-V|-f|-F|-r name] [rtcdev]\n",
+				argv[0]);
+			return KSFT_FAIL;
+		}
 	}
 
+	/*
+	 * Rewind getopt() so test_harness_run() can parse the options again.
+	 * Only do this after the loop above has consumed every option, as
+	 * getopt() keeps its position within grouped options (e.g. "-ld").
+	 */
+	optind = 1;
+
+	/* -h and -l are handled by the harness and need no RTC device */
+	if (skip_dev_check)
+		return test_harness_run(argc, argv);
+
 	/* Run the test if rtc_file is accessible */
 	if (access(rtc_file, R_OK) == 0)
 		ret = test_harness_run(argc, argv);

base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.56.0.542.g3ef89b7020-goog