drm: add support for DMA-BUFs

Mesa's Vulkan WSI still uses wl_drm when modifiers aren't supported.
This has been fixed in [1] but will take some time to be propagated
to users. In the meantime, add a fallback.

[1]: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4942

include/wlr/types/wlr_drm.h

@@ -13,6 +13,15 @@
 
 struct wlr_renderer;
 
+struct wlr_drm_buffer {
+	struct wlr_buffer base;
+
+	struct wl_resource *resource; // can be NULL if the client destroyed it
+	struct wlr_dmabuf_attributes dmabuf;
+
+	struct wl_listener release;
+};
+
 /**
  * A stub implementation of Mesa's wl_drm protocol.
  *
@@ -21,6 +30,7 @@ struct wlr_renderer;
  */
 struct wlr_drm {
 	struct wl_global *global;
+	struct wlr_renderer *renderer;
 	char *node_name;
 
 	struct {
@@ -28,8 +38,14 @@ struct wlr_drm {
 	} events;
 
 	struct wl_listener display_destroy;
+	struct wl_listener renderer_destroy;
 };
 
+bool wlr_drm_buffer_is_resource(struct wl_resource *resource);
+
+struct wlr_drm_buffer *wlr_drm_buffer_from_resource(
+	struct wl_resource *resource);
+
 struct wlr_drm *wlr_drm_create(struct wl_display *display,
 	struct wlr_renderer *renderer);
 

types/wlr_drm.c

@@ -1,9 +1,12 @@
 #define _POSIX_C_SOURCE 200809L
 #include <assert.h>
+#include <drm_fourcc.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <xf86drm.h>
+#include <wlr/render/drm_format_set.h>
 #include <wlr/render/wlr_renderer.h>
+#include <wlr/types/wlr_buffer.h>
 #include <wlr/types/wlr_drm.h>
 #include <wlr/util/log.h>
 #include "drm-protocol.h"
@@ -11,6 +14,69 @@
 
 #define WLR_DRM_VERSION 2
 
+static void buffer_handle_destroy(struct wl_client *client,
+		struct wl_resource *resource) {
+	wl_resource_destroy(resource);
+}
+
+static const struct wl_buffer_interface wl_buffer_impl = {
+	.destroy = buffer_handle_destroy,
+};
+
+static const struct wlr_buffer_impl buffer_impl;
+
+static struct wlr_drm_buffer *drm_buffer_from_buffer(
+		struct wlr_buffer *buffer) {
+	assert(buffer->impl == &buffer_impl);
+	return (struct wlr_drm_buffer *)buffer;
+}
+
+static void buffer_destroy(struct wlr_buffer *wlr_buffer) {
+	struct wlr_drm_buffer *buffer = drm_buffer_from_buffer(wlr_buffer);
+	if (buffer->resource != NULL) {
+		wl_resource_set_user_data(buffer->resource, NULL);
+	}
+	wlr_dmabuf_attributes_finish(&buffer->dmabuf);
+	wl_list_remove(&buffer->release.link);
+	free(buffer);
+}
+
+static bool buffer_get_dmabuf(struct wlr_buffer *wlr_buffer,
+		struct wlr_dmabuf_attributes *dmabuf) {
+	struct wlr_drm_buffer *buffer = drm_buffer_from_buffer(wlr_buffer);
+	*dmabuf = buffer->dmabuf;
+	return true;
+}
+
+static const struct wlr_buffer_impl buffer_impl = {
+	.destroy = buffer_destroy,
+	.get_dmabuf = buffer_get_dmabuf,
+};
+
+bool wlr_drm_buffer_is_resource(struct wl_resource *resource) {
+	return wl_resource_instance_of(resource, &wl_buffer_interface,
+		&wl_buffer_impl);
+}
+
+struct wlr_drm_buffer *wlr_drm_buffer_from_resource(
+		struct wl_resource *resource) {
+	assert(wlr_drm_buffer_is_resource(resource));
+	return wl_resource_get_user_data(resource);
+}
+
+static void buffer_handle_resource_destroy(struct wl_resource *resource) {
+	struct wlr_drm_buffer *buffer = wlr_drm_buffer_from_resource(resource);
+	buffer->resource = NULL;
+	wlr_buffer_drop(&buffer->base);
+}
+
+static void buffer_handle_release(struct wl_listener *listener, void *data) {
+	struct wlr_drm_buffer *buffer = wl_container_of(listener, buffer, release);
+	if (buffer->resource != NULL) {
+		wl_buffer_send_release(buffer->resource);
+	}
+}
+
 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
@@ -36,9 +102,39 @@ 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) {
+	struct wlr_dmabuf_attributes dmabuf = {
+		.width = width,
+		.height = height,
+		.format = format,
+		.modifier = DRM_FORMAT_MOD_INVALID,
+		.n_planes = 1,
+		.offset[0] = offset0,
+		.stride[0] = stride0,
+		.fd[0] = fd,
+	};
+
+	struct wlr_drm_buffer *buffer = calloc(1, sizeof(*buffer));
+	if (buffer == NULL) {
 		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");
+		wl_resource_post_no_memory(resource);
+		return;
+	}
+	wlr_buffer_init(&buffer->base, &buffer_impl, width, height);
+
+	buffer->resource = wl_resource_create(client, &wl_buffer_interface, 1, id);
+	if (buffer->resource == NULL) {
+		free(buffer);
+		close(fd);
+		wl_resource_post_no_memory(resource);
+		return;
+	}
+	wl_resource_set_implementation(buffer->resource, &wl_buffer_impl, buffer,
+		buffer_handle_resource_destroy);
+
+	buffer->dmabuf = dmabuf;
+
+	buffer->release.notify = buffer_handle_release;
+	wl_signal_add(&buffer->base.events.release, &buffer->release);
 }
 
 static const struct wl_drm_interface drm_impl = {
@@ -62,20 +158,39 @@ static void drm_bind(struct wl_client *client, void *data,
 
 	wl_drm_send_device(resource, drm->node_name);
 	wl_drm_send_capabilities(resource, WL_DRM_CAPABILITY_PRIME);
+
+	const struct wlr_drm_format_set *formats =
+		wlr_renderer_get_dmabuf_texture_formats(drm->renderer);
+	if (formats == NULL) {
+		return;
 	}
 
-static void handle_display_destroy(struct wl_listener *listener, void *data) {
-	struct wlr_drm *drm = wl_container_of(listener, drm, display_destroy);
+	for (size_t i = 0; i < formats->len; i++) {
+		wl_drm_send_format(resource, formats->formats[i]->format);
+	}
+}
 
+static void drm_destroy(struct wlr_drm *drm) {
 	wlr_signal_emit_safe(&drm->events.destroy, NULL);
 
 	wl_list_remove(&drm->display_destroy.link);
+	wl_list_remove(&drm->renderer_destroy.link);
 
 	free(drm->node_name);
 	wl_global_destroy(drm->global);
 	free(drm);
 }
 
+static void handle_display_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_drm *drm = wl_container_of(listener, drm, display_destroy);
+	drm_destroy(drm);
+}
+
+static void handle_renderer_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_drm *drm = wl_container_of(listener, drm, renderer_destroy);
+	drm_destroy(drm);
+}
+
 struct wlr_drm *wlr_drm_create(struct wl_display *display,
 		struct wlr_renderer *renderer) {
 	int drm_fd = wlr_renderer_get_drm_fd(renderer);
@@ -111,6 +226,7 @@ struct wlr_drm *wlr_drm_create(struct wl_display *display,
 	}
 
 	drm->node_name = node_name;
+	drm->renderer = renderer;
 	wl_signal_init(&drm->events.destroy);
 
 	drm->global = wl_global_create(display, &wl_drm_interface, WLR_DRM_VERSION,
@@ -124,5 +240,8 @@ struct wlr_drm *wlr_drm_create(struct wl_display *display,
 	drm->display_destroy.notify = handle_display_destroy;
 	wl_display_add_destroy_listener(display, &drm->display_destroy);
 
+	drm->renderer_destroy.notify = handle_renderer_destroy;
+	wl_signal_add(&renderer->events.destroy, &drm->renderer_destroy);
+
 	return drm;
 }