[PATCH i-g-t v4 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 | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_kms.h |  1 +
 2 files changed, 66 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index d0b6c70f135754d0a413f73a0f8e5b24a208a2b3..93d5a0d64df9954f7da8254ee35a0fd887d31d78 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -7246,6 +7246,29 @@ double igt_default_display_detect_timeout(void)
 	return timeout;
 }
 
+static drmModeConnectorPtr igt_wait_for_connector(int drm_fd, unsigned int connector_id,
+						  double timeout)
+{
+	drmModeConnectorPtr connector = NULL;
+	struct timespec start, end;
+
+	connector = drmModeGetConnector(drm_fd, connector_id);
+	/*
+	 * This time is required as sometimes some id in the connector list are not totally
+	 * ready or can disappear
+	 */
+	clock_gettime(CLOCK_MONOTONIC, &start);
+	end = start;
+
+	while (!connector &&
+	       igt_time_elapsed(&start, &end) <= timeout) {
+		connector = drmModeGetConnector(drm_fd, connector_id);
+		clock_gettime(CLOCK_MONOTONIC, &end);
+	}
+
+	return connector;
+}
+
 /**
  * igt_wait_for_connector_status:
  * @drm_fd: drm file descriptor
@@ -7284,3 +7307,45 @@ bool igt_wait_for_connector_status(int drm_fd, unsigned int connector_id, double
 		  connector_id);
 	return false;
 }
+
+/**
+ * igt_get_connected_connectors:
+ *
+ * @drm_fd: DRM file description
+ * @connector_ids: Out pointer for the list of connector ids connected. It must be freed by the
+ * caller.
+ *
+ * This will probe all the connectors and return the list of all
+ * connected connectors.
+ * Returns: The number of connectors in @connector_ids
+ */
+int igt_get_connected_connectors(int drm_fd, uint32_t **connector_ids)
+{
+	int connected_count = 0;
+	double timeout = igt_default_display_detect_timeout();
+	drmModeResPtr resources;
+
+	*connector_ids = NULL;
+
+	resources = drmModeGetResources(drm_fd);
+	for (int j = 0; j < resources->count_connectors; j++) {
+		drmModeConnectorPtr connector = igt_wait_for_connector(drm_fd,
+								       resources->connectors[j],
+								       timeout);
+
+		if (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 6d5582290f61d1a4151dd8e8448fc26c660a1536..520d1b2f2056a21bcf25be36da32a63a17bfe364 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -1281,5 +1281,6 @@ double igt_default_display_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__ */

-- 
2.47.1