Add a stub wl_drm implementation

This will allow us to remove all of our EGL wl_drm support code
and remove some weird stuff we need just for wl_drm support. In
particular, wl_drm buffers coming from the EGL implementation
can't easily be wrapped into a wlr_buffer properly.

include/wlr/types/wlr_drm.h

@@ -0,0 +1,36 @@
+/*
+ * This an unstable interface of wlroots. No guarantees are made regarding the
+ * future consistency of this API.
+ */
+#ifndef WLR_USE_UNSTABLE
+#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
+#endif
+
+#ifndef WLR_TYPES_WLR_DRM_H
+#define WLR_TYPES_WLR_DRM_H
+
+#include <wayland-server-protocol.h>
+
+struct wlr_renderer;
+
+/**
+ * A stub implementation of Mesa's wl_drm protocol.
+ *
+ * It only implements the minimum necessary for modern clients to behave
+ * properly. In particular, flink handles are left unimplemented.
+ */
+struct wlr_drm {
+	struct wl_global *global;
+	char *node_name;
+
+	struct {
+		struct wl_signal destroy;
+	} events;
+
+	struct wl_listener display_destroy;
+};
+
+struct wlr_drm *wlr_drm_create(struct wl_display *display,
+	struct wlr_renderer *renderer);
+
+#endif

types/meson.build

@@ -21,6 +21,7 @@ wlr_files += files(
 	'wlr_compositor.c',
 	'wlr_cursor.c',
 	'wlr_data_control_v1.c',
+	'wlr_drm.c',
 	'wlr_export_dmabuf_v1.c',
 	'wlr_foreign_toplevel_management_v1.c',
 	'wlr_fullscreen_shell_v1.c',

types/wlr_drm.c

@@ -0,0 +1,128 @@
+#define _POSIX_C_SOURCE 200809L
+#include <assert.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <xf86drm.h>
+#include <wlr/render/wlr_renderer.h>
+#include <wlr/types/wlr_drm.h>
+#include <wlr/util/log.h>
+#include "drm-protocol.h"
+#include "util/signal.h"
+
+#define WLR_DRM_VERSION 2
+
+static void drm_handle_authenticate(struct wl_client *client,
+		struct wl_resource *resource, uint32_t id) {
+	// We only use render nodes, which don't need authentication
+	wl_drm_send_authenticated(resource);
+}
+
+static void drm_handle_create_buffer(struct wl_client *client,
+		struct wl_resource *resource, uint32_t id, uint32_t name, int32_t width,
+		int32_t height, uint32_t stride, uint32_t format) {
+	wl_resource_post_error(resource, WL_DRM_ERROR_INVALID_NAME,
+		"Flink handles are not supported, use DMA-BUF instead");
+}
+
+static void drm_handle_create_planar_buffer(struct wl_client *client,
+		struct wl_resource *resource, uint32_t id, uint32_t name, int32_t width,
+		int32_t height, uint32_t format, int32_t offset0, int32_t stride0,
+		int32_t offset1, int32_t stride1, int32_t offset2, int32_t stride2) {
+	wl_resource_post_error(resource, WL_DRM_ERROR_INVALID_NAME,
+		"Flink handles are not supported, use DMA-BUF instead");
+}
+
+static void drm_handle_create_prime_buffer(struct wl_client *client,
+		struct wl_resource *resource, uint32_t id, int fd, int32_t width,
+		int32_t height, uint32_t format, int32_t offset0, int32_t stride0,
+		int32_t offset1, int32_t stride1, int32_t offset2, int32_t stride2) {
+	close(fd);
+	wl_resource_post_error(resource, WL_DRM_ERROR_INVALID_NAME,
+		"DMA-BUF imports via wl_drm are not supported, use linux-dmabuf instead");
+}
+
+static const struct wl_drm_interface drm_impl = {
+	.authenticate = drm_handle_authenticate,
+	.create_buffer = drm_handle_create_buffer,
+	.create_planar_buffer = drm_handle_create_planar_buffer,
+	.create_prime_buffer = drm_handle_create_prime_buffer,
+};
+
+static void drm_bind(struct wl_client *client, void *data,
+		uint32_t version, uint32_t id) {
+	struct wlr_drm *drm = data;
+
+	struct wl_resource *resource = wl_resource_create(client,
+		&wl_drm_interface, version, id);
+	if (resource == NULL) {
+		wl_client_post_no_memory(client);
+		return;
+	}
+	wl_resource_set_implementation(resource, &drm_impl, drm, NULL);
+
+	wl_drm_send_device(resource, drm->node_name);
+	wl_drm_send_capabilities(resource, WL_DRM_CAPABILITY_PRIME);
+}
+
+static void handle_display_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_drm *drm = wl_container_of(listener, drm, display_destroy);
+
+	wlr_signal_emit_safe(&drm->events.destroy, NULL);
+
+	wl_list_remove(&drm->display_destroy.link);
+
+	free(drm->node_name);
+	wl_global_destroy(drm->global);
+	free(drm);
+}
+
+struct wlr_drm *wlr_drm_create(struct wl_display *display,
+		struct wlr_renderer *renderer) {
+	int drm_fd = wlr_renderer_get_drm_fd(renderer);
+	if (drm_fd < 0) {
+		wlr_log(WLR_ERROR, "Failed to get DRM FD from renderer");
+		return NULL;
+	}
+
+	drmDevice *dev = NULL;
+	if (drmGetDevice2(drm_fd, 0, &dev) != 0) {
+		wlr_log(WLR_ERROR, "drmGetDevice2 failed");
+		return NULL;
+	}
+
+	char *node_name = NULL;
+	if (dev->available_nodes & (1 << DRM_NODE_RENDER)) {
+		node_name = strdup(dev->nodes[DRM_NODE_RENDER]);
+	} else {
+		assert(dev->available_nodes & (1 << DRM_NODE_PRIMARY));
+		wlr_log(WLR_DEBUG, "No DRM render node available, "
+			"falling back to primary node '%s'", dev->nodes[DRM_NODE_PRIMARY]);
+		node_name = strdup(dev->nodes[DRM_NODE_PRIMARY]);
+	}
+	drmFreeDevice(&dev);
+	if (node_name == NULL) {
+		return NULL;
+	}
+
+	struct wlr_drm *drm = calloc(1, sizeof(*drm));
+	if (drm == NULL) {
+		free(node_name);
+		return NULL;
+	}
+
+	drm->node_name = node_name;
+	wl_signal_init(&drm->events.destroy);
+
+	drm->global = wl_global_create(display, &wl_drm_interface, WLR_DRM_VERSION,
+		drm, drm_bind);
+	if (drm->global == NULL) {
+		free(drm->node_name);
+		free(drm);
+		return NULL;
+	}
+
+	drm->display_destroy.notify = handle_display_destroy;
+	wl_display_add_destroy_listener(display, &drm->display_destroy);
+
+	return drm;
+}