libdm: add dm_message_supports_precise_timestamps()

Add a function to test whether the kernel precise_timestamps
feature is available in the current device-mapper driver version.

Presence of precise_timestamps also implies the availability of
latency histograms.

1 files changed, 14 insertions, 0 deletions

diff --git a/libdm/ioctl/libdm-iface.c b/libdm/ioctl/libdm-iface.c
index 73af12b7a..fe0bffacd 100644
--- a/libdm/ioctl/libdm-iface.c
+++ b/libdm/ioctl/libdm-iface.c
@@ -604,6 +604,20 @@ static int dm_inactive_supported(void)
 	return inactive_supported;
 }
 
+int dm_message_supports_precise_timestamps(void)
+{
+	/*
+	 * 4.32.0 supports "precise_timestamps" and "histogram:" options
+	 * to @stats_create messages but lacks the ability to report
+	 * these properties via a subsequent @stats_list: require at
+	 * least 4.33.0 in order to use these features.
+	 */
+	if (dm_check_version() && _dm_version >= 4)
+		if (_dm_version_minor >= 33)
+			return 1;
+	return 0;
+}
+
 void *dm_get_next_target(struct dm_task *dmt, void *next,
 			 uint64_t *start, uint64_t *length,
 			 char **target_type, char **params)