[PATCH i-g-t 3/5] lib/igt_kms: Add function to list connected connectors

[Louis Chauvet]

Introduce the igt_get_connected_connectors() function, which returns a
list of connector IDs that are currently connected according to DRM.

This function includes a timeout mechanism because connectors can be
unplugged at any time. Also, especially with MST, the connector can be
listed by drmModeGetResources() but not yet accessible with
drmModeGetConnector().

Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
---
 lib/igt_kms.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_kms.h |  1 +
 2 files changed, 55 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index b1d937b4d91e..d4fe4ee7ae4a 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -6767,3 +6767,57 @@ bool igt_wait_for_connector_status(int drm_fd, unsigned int connector_id, double
 		  connector_id);
 	return false;
 }
+
+/**
+ * igt_get_connected_connectors - List all connectors reported as CONNECTED by DRM.
+ *
+ * @drm_fd: DRM file description
+ * @connector_ids: out pointer for the list of connector ids connected. It must be freed by the
+ * caller.
+ *
+ * The returns value is the number of connectors
+ */
+int igt_get_connected_connectors(int drm_fd, uint32_t **connector_ids)
+{
+	int connected_count = 0;
+	drmModeResPtr resources;
+	struct timespec start, end;
+
+	*connector_ids = malloc(0);
+
+	resources = drmModeGetResources(drm_fd);
+	for (int j = 0; j < resources->count_connectors; j++) {
+		drmModeConnectorPtr connector = NULL;
+
+		connector = drmModeGetConnector(drm_fd, resources->connectors[j]);
+		/*
+		 * This time is required as sometimes some id in the connector list are not totally
+		 * ready or can disappear
+		 */
+		clock_gettime(CLOCK_MONOTONIC, &start);
+		clock_gettime(CLOCK_MONOTONIC, &end);
+		while (!connector &&
+		       igt_time_elapsed(&start, &end) < igt_default_detect_timeout()) {
+			connector = drmModeGetConnector(drm_fd, resources->connectors[j]);
+			clock_gettime(CLOCK_MONOTONIC, &end);
+		}
+
+		if (igt_time_elapsed(&start, &end) < igt_default_detect_timeout()) {
+			igt_assert(connector);
+
+			if (connector->connection == DRM_MODE_CONNECTED) {
+				*connector_ids = reallocarray(*connector_ids,
+							      connected_count
+							      + 1, sizeof(**connector_ids));
+				igt_assert(*connector_ids);
+				(*connector_ids)[connected_count] = resources->connectors[j];
+				connected_count++;
+			}
+			drmModeFreeConnector(connector);
+		}
+	}
+	drmModeFreeResources(resources);
+
+	return
+	    connected_count;
+}
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index 33f663d54463..b3ff0cdda36f 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -1236,5 +1236,6 @@ float igt_default_detect_timeout(void);
 
 bool igt_wait_for_connector_status(int drm_fd, unsigned int connector_id, double timeout,
 				   int drm_mode);
+int igt_get_connected_connectors(int drm_fd, uint32_t **connector_ids);
 
 #endif /* __IGT_KMS_H__ */

-- 
2.44.2