backend/drm: populate wlr_output.port

backend/drm/backend.c

@@ -13,6 +13,7 @@
 #include <xf86drm.h>
 #include "backend/drm/drm.h"
 #include "backend/drm/fb.h"
+#include "backend/drm/util.h"
 #include "render/drm_format_set.h"
 
 struct wlr_drm_backend *get_drm_backend_from_backend(
@@ -227,6 +228,9 @@ struct wlr_backend *wlr_drm_backend_create(struct wlr_session *session,
 	wlr_log(WLR_INFO, "Initializing DRM backend for %s (%s)", name, version->name);
 	drmFreeVersion(version);
 
+	drmDevice *dev_info = NULL;
+	drmGetDevice2(dev->fd, 0, &dev_info);
+
 	struct wlr_drm_backend *drm = calloc(1, sizeof(*drm));
 	if (!drm) {
 		wlr_log_errno(WLR_ERROR, "Allocation failed");
@@ -245,6 +249,9 @@ struct wlr_backend *wlr_drm_backend_create(struct wlr_session *session,
 	drm->fd = dev->fd;
 	drm->name = name;
 
+	drm->bus = get_drm_bus_str(dev_info);
+	drmFreeDevice(&dev_info);
+
 	if (parent != NULL) {
 		drm->parent = get_drm_backend_from_backend(parent);
 

backend/drm/drm.c

@@ -1593,6 +1593,92 @@ static drmModeModeInfo *connector_get_current_mode(struct wlr_drm_connector *wlr
 	}
 }
 
+static struct wlr_drm_connector *find_drm_connector_by_id(struct wlr_drm_backend *drm, uint32_t id) {
+	struct wlr_drm_connector *conn = NULL;
+	wl_list_for_each(conn, &drm->connectors, link) {
+		if (conn->id == id) {
+			return conn;
+		}
+	}
+	return NULL;
+}
+
+static bool connector_write_root_port(struct wlr_drm_connector *wlr_conn, FILE *f) {
+	struct wlr_drm_backend *drm = wlr_conn->backend;
+
+	size_t seq_num = 0;
+	struct wlr_drm_connector *c;
+	wl_list_for_each(c, &drm->connectors, link) {
+		seq_num++;
+		if (c == wlr_conn) {
+			break;
+		}
+	}
+
+	return fprintf(f, "%s/connector-%zu", drm->bus, seq_num) > 0;
+}
+
+static bool connector_write_port(struct wlr_drm_connector *wlr_conn, FILE *f);
+
+static bool connector_write_nested_port(struct wlr_drm_connector *wlr_conn, FILE *f) {
+	struct wlr_drm_backend *drm = wlr_conn->backend;
+	bool ok = false;
+
+	size_t size = 0;
+	void *path_prop_data = get_drm_prop_blob(drm->fd, wlr_conn->id, wlr_conn->props.path, &size);
+	if (path_prop_data == NULL) {
+		goto out;
+	}
+
+	uint32_t parent_conn_id = 0;
+	const char *child_path = NULL;
+	if (!parse_dp_mst_path(path_prop_data, &parent_conn_id, &child_path)) {
+		goto out;
+	}
+	struct wlr_drm_connector *parent = find_drm_connector_by_id(drm, parent_conn_id);
+	if (parent == NULL) {
+		goto out;
+	}
+
+	if (!connector_write_port(parent, f)) {
+		goto out;
+	}
+
+	ok = fprintf(f, "/mst-%s", child_path) > 0;
+
+out:
+	free(path_prop_data);
+	return ok;
+}
+
+static bool connector_write_port(struct wlr_drm_connector *wlr_conn, FILE *f) {
+	if (wlr_conn->props.path != 0) {
+		return connector_write_nested_port(wlr_conn, f);
+	} else {
+		return connector_write_root_port(wlr_conn, f);
+	}
+}
+
+static char *connector_get_port(struct wlr_drm_connector *wlr_conn) {
+	if (wlr_conn->backend->bus == NULL) {
+		return NULL;
+	}
+
+	char *str = NULL;
+	size_t str_size = 0;
+	FILE *f = open_memstream(&str, &str_size);
+	if (f == NULL) {
+		return NULL;
+	}
+
+	bool ok = connector_write_port(wlr_conn, f);
+	if (fclose(f) != 0 || !ok) {
+		return NULL;
+	}
+
+	return str;
+}
+
 static bool connect_drm_connector(struct wlr_drm_connector *wlr_conn,
 		const drmModeConnector *drm_conn) {
 	struct wlr_drm_backend *drm = wlr_conn->backend;
@@ -1720,6 +1806,9 @@ static bool connect_drm_connector(struct wlr_drm_connector *wlr_conn,
 	wlr_output_set_description(output, description);
 
 	free(subconnector);
+
+	output->port = connector_get_port(wlr_conn);
+
 	wlr_conn->status = DRM_MODE_CONNECTED;
 	return true;
 }

backend/drm/util.c

@@ -270,3 +270,44 @@ void generate_cvt_mode(drmModeModeInfo *mode, int hdisplay, int vdisplay,
 	};
 	snprintf(mode->name, sizeof(mode->name), "%dx%d", hdisplay, vdisplay);
 }
+
+char *get_drm_bus_str(const drmDevice *dev) {
+	char buf[128];
+	switch (dev->bustype) {
+	case DRM_BUS_PCI:;
+		const drmPciBusInfo *pci = dev->businfo.pci;
+		snprintf(buf, sizeof(buf), "pci-%04" PRIx16 ":%02" PRIx8 ":%02" PRIx8 ".%" PRIu8,
+			pci->domain, pci->bus, pci->dev, pci->func);
+		return strdup(buf);
+	case DRM_BUS_PLATFORM:;
+		const drmPlatformBusInfo *platform = dev->businfo.platform;
+		size_t str_size = strlen("platform-") + strlen(platform->fullname) + 1;
+		char *str = malloc(str_size);
+		if (str == NULL) {
+			return NULL;
+		}
+		snprintf(str, str_size, "platform-%s", platform->fullname);
+		return str;
+	}
+	return NULL;
+}
+
+bool parse_dp_mst_path(const char *path, uint32_t *parent_conn_id, const char **child_path) {
+	const char prefix[] = "mst:";
+	if (strncmp(path, prefix, strlen(prefix)) != 0) {
+		return false;
+	}
+	path = &path[strlen(prefix)];
+
+	char *id_end;
+	errno = 0;
+	unsigned long id = strtoul(path, &id_end, 10);
+	if (errno != 0 || id_end[0] != '-' || id > UINT32_MAX) {
+		wlr_log(WLR_ERROR, "Malformed PATH DP-MST property: invalid parent connector ID");
+		return false;
+	}
+
+	*parent_conn_id = (uint32_t)id;
+	*child_path = &id_end[1];
+	return true;
+}

include/backend/drm/drm.h

@@ -92,7 +92,7 @@ struct wlr_drm_backend {
 	bool addfb2_modifiers;
 
 	int fd;
-	char *name;
+	char *name, *bus;
 	struct wlr_device *dev;
 	struct liftoff_device *liftoff;
 

include/backend/drm/util.h

@@ -38,4 +38,7 @@ void match_connectors_with_crtcs(size_t num_conns,
 	size_t num_crtcs, const uint32_t prev_crtcs[static restrict num_crtcs],
 	uint32_t new_crtcs[static restrict num_crtcs]);
 
+char *get_drm_bus_str(const drmDevice *dev);
+bool parse_dp_mst_path(const char *path, uint32_t *parent_conn_id, const char **child_path);
+
 #endif