[PATCH v4 2/3] kselftest: alsa: optimization for SNDRV_CTL_ELEM_ACCESS_VOLATILE

[Mark Brown]

From: Takashi Sakamoto <o-takashi at sakamocchi.jp>

The volatile attribute of control element means that the hardware can
voluntarily change the state of control element independent of any
operation by software. ALSA control core necessarily sends notification
to userspace subscribers for any change from userspace application, while
it doesn't for the hardware's voluntary change.

This commit adds optimization for the attribute. Even if read value is
different from written value, the test reports success as long as the
target control element has the attribute. On the other hand, the
difference is itself reported for developers' convenience.

Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
Link: https://lore.kernel.org/r/Ya7TAHdMe9i41bsC@workstation
[Fix comment style as suggested by Shuah -- broonie]
Reviewed-by: Shuah Khan <skhan at linuxfoundation.org>
Signed-off-by: Mark Brown <broonie at kernel.org>
---
 tools/testing/selftests/alsa/mixer-test.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/alsa/mixer-test.c b/tools/testing/selftests/alsa/mixer-test.c
index ab51cf7b9e03..f65a9046e708 100644
--- a/tools/testing/selftests/alsa/mixer-test.c
+++ b/tools/testing/selftests/alsa/mixer-test.c
@@ -307,9 +307,15 @@ bool show_mismatch(struct ctl_data *ctl, int index,
 	}
 
 	if (expected_int != read_int) {
-		ksft_print_msg("%s.%d expected %lld but read %lld\n",
-			       ctl->name, index, expected_int, read_int);
-		return true;
+		/*
+		 * NOTE: The volatile attribute means that the hardware
+		 * can voluntarily change the state of control element
+		 * independent of any operation by software.  
+		 */
+		bool is_volatile = snd_ctl_elem_info_is_volatile(ctl->info);
+		ksft_print_msg("%s.%d expected %lld but read %lld, is_volatile %d\n",
+			       ctl->name, index, expected_int, read_int, is_volatile);
+		return !is_volatile;
 	} else {
 		return false;
 	}
-- 
2.30.2