Chamelium: Handle getting port connector if it's MST.

[Why]
When getting a connector for a port, the connector ID might be invalid
after a replug if it's an MST connector. Getting the connector with just
the connector ID will not always work.

[How]
Check if the connector is MST by checking the port's connector path.
If it is, iterate through all connectors until a connector with a
matching path is found.

TEST=./kms_chamelium --run-subtest dp-hpd [on intel Volteer board with
Chamelium V3 connected]

Signed-off-by: Mark Yacoub <markyacoub@chromium.org>
Reviewed-by: Lyude Paul <lyude@redhat.com>

lib/igt_chamelium.c

@@ -182,6 +182,20 @@ unsigned int chamelium_port_get_type(const struct chamelium_port *port) {
 	return port->type;
 }
 
+/**
+ * chamelium_port_get_name:
+ * @port: The chamelium port to retrieve the name of
+ *
+ * Gets the name of the DRM connector corresponding to the given Chamelium
+ * port.
+ *
+ * Returns: the name of the DRM connector
+ */
+const char *chamelium_port_get_name(struct chamelium_port *port)
+{
+	return port->name;
+}
+
 /**
  * chamelium_port_get_connector:
  * @chamelium: The Chamelium instance to use
@@ -197,30 +211,79 @@ drmModeConnector *chamelium_port_get_connector(struct chamelium *chamelium,
 					       struct chamelium_port *port,
 					       bool reprobe)
 {
-	drmModeConnector *connector;
+	typedef drmModeConnectorPtr (*getConnectorPtr)(int fd,
+						       uint32_t connector_id);
 
-	if (reprobe)
-		connector = drmModeGetConnector(chamelium->drm_fd,
-						port->connector_id);
-	else
-		connector = drmModeGetConnectorCurrent(
-		    chamelium->drm_fd, port->connector_id);
+	drmModeRes *res = NULL;
+	int i;
 
-	return connector;
-}
+	bool is_mst_port = !!port->connector_path;
+	getConnectorPtr getConnector = reprobe ? &drmModeGetConnector :
+						 &drmModeGetConnectorCurrent;
+	int drm_fd = chamelium->drm_fd;
+	drmModeConnector *connector = getConnector(drm_fd, port->connector_id);
 
-/**
- * chamelium_port_get_name:
- * @port: The chamelium port to retrieve the name of
- *
- * Gets the name of the DRM connector corresponding to the given Chamelium
- * port.
- *
- * Returns: the name of the DRM connector
- */
-const char *chamelium_port_get_name(struct chamelium_port *port)
-{
-	return port->name;
+	/* If the port isn't MST, then the connector ID should be consistent to grab the connector. */
+	if (!is_mst_port) {
+		return connector;
+	}
+
+	/* If the port is MST, then we need to find the connector ID from the path. */
+
+	/* In case the connector ID is still valid, do a quick check if we're have the connector we expect. 
+	 * Otherwise, read the new resources and find the new connector we're looking for. */
+	if (connector) {
+		drmModePropertyBlobPtr path_blob =
+			kmstest_get_path_blob(drm_fd, connector->connector_id);
+		if (path_blob) {
+			bool is_correct_connector =
+				strcmp(port->connector_path, path_blob->data) ==
+				0;
+			drmModeFreePropertyBlob(path_blob);
+			if (is_correct_connector)
+				return connector;
+		}
+
+		drmModeFreeConnector(connector);
+		connector = NULL;
+	}
+
+	res = drmModeGetResources(drm_fd);
+	for (i = 0; i < res->count_connectors; i++) {
+		drmModePropertyBlobPtr path_blob = NULL;
+
+		connector = getConnector(drm_fd, res->connectors[i]);
+		/* Check if the connector is not disconnected and in zombie mode. */
+		if (!connector)
+			continue;
+		/* Check if the connector is MST. */
+		path_blob =
+			kmstest_get_path_blob(drm_fd, connector->connector_id);
+		if (!path_blob)
+			continue;
+
+		if (strcmp(path_blob->data, port->connector_path) == 0) {
+			char connector_name[50];
+			/* At finding the connector, update its metadata. */
+			port->connector_id = connector->connector_id;
+
+			snprintf(connector_name, 50, "%s-%u",
+				 kmstest_connector_type_str(
+					 connector->connector_type),
+				 connector->connector_type_id);
+			port->name = strdup(connector_name);
+
+			goto out;
+		}
+
+		drmModeFreePropertyBlob(path_blob);
+		drmModeFreeConnector(connector);
+		connector = NULL;
+	}
+
+out:
+	drmModeFreeResources(res);
+	return connector;
 }
 
 /**
@@ -2862,7 +2925,7 @@ struct chamelium *chamelium_init(int drm_fd)
 		bool type_mismatch = false;
 		struct chamelium_port * port = &chamelium->ports[i];
 		drmModeConnectorPtr connector =
-			drmModeGetConnectorCurrent(drm_fd, port->connector_id);
+			chamelium_port_get_connector(chamelium, port, false);
 
 		igt_assert(connector != NULL);
 

lib/igt_kms.c

@@ -1786,6 +1786,22 @@ bool kmstest_get_connector_config(int drm_fd, uint32_t connector_id,
 					 config, 0);
 }
 
+drmModePropertyBlobPtr kmstest_get_path_blob(int drm_fd, uint32_t connector_id)
+{
+	uint64_t path_blob_id = 0;
+	drmModePropertyBlobPtr path_blob = NULL;
+
+	if (!kmstest_get_property(drm_fd, connector_id,
+				  DRM_MODE_OBJECT_CONNECTOR, "PATH", NULL,
+				  &path_blob_id, NULL)) {
+		return NULL;
+	}
+
+	path_blob = drmModeGetPropertyBlob(drm_fd, path_blob_id);
+	igt_assert(path_blob);
+	return path_blob;
+}
+
 /**
  * kmstest_probe_connector_config:
  * @drm_fd: DRM fd

lib/igt_kms.h

@@ -234,6 +234,7 @@ bool kmstest_get_connector_default_mode(int drm_fd, drmModeConnector *connector,
 bool kmstest_get_connector_config(int drm_fd, uint32_t connector_id,
 				  unsigned long crtc_idx_mask,
 				  struct kmstest_connector_config *config);
+drmModePropertyBlobPtr kmstest_get_path_blob(int drm_fd, uint32_t connector_id);
 bool kmstest_probe_connector_config(int drm_fd, uint32_t connector_id,
 				    unsigned long crtc_idx_mask,
 				    struct kmstest_connector_config *config);