Merge pull request #2 from ascent12/master

DRM backend + Session interface + EGL

3 files changed, 735 insertions, 0 deletions

diff --git a/backend/drm/backend.c b/backend/drm/backend.c
new file mode 100644
index 00000000..0da84745
--- /dev/null
+++ b/backend/drm/backend.c
@@ -0,0 +1,103 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <wayland-server.h>
+
+#include <wlr/session.h>
+#include <wlr/common/list.h>
+
+#include "backend.h"
+#include "backend/drm/backend.h"
+#include "backend/drm/drm.h"
+#include "backend/drm/udev.h"
+#include "common/log.h"
+
+static bool wlr_drm_backend_init(struct wlr_backend_state *state) {
+	wlr_drm_scan_connectors(state);
+	return true;
+}
+
+static void wlr_drm_backend_destroy(struct wlr_backend_state *state) {
+	if (!state) {
+		return;
+	}
+	// TODO: free outputs in shared backend code
+	wlr_drm_renderer_free(&state->renderer);
+	wlr_udev_free(&state->udev);
+	wlr_session_close_file(state->session, state->fd);
+	wlr_session_finish(state->session);
+	wl_event_source_remove(state->drm_event);
+	free(state);
+}
+
+static struct wlr_backend_impl backend_impl = {
+	.init = wlr_drm_backend_init,
+	.destroy = wlr_drm_backend_destroy
+};
+
+struct wlr_backend *wlr_drm_backend_create(struct wl_display *display,
+		struct wlr_session *session) {
+	struct wlr_backend_state *state = calloc(1, sizeof(struct wlr_backend_state));
+	if (!state) {
+		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		return NULL;
+	}
+
+	struct wlr_backend *backend = wlr_backend_create(&backend_impl, state);
+	if (!backend) {
+		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		return NULL;
+	}
+
+	state->backend = backend;
+	state->session = session;
+	state->outputs = list_create();
+	if (!state->outputs) {
+		wlr_log(L_ERROR, "Failed to allocate list");
+		goto error_backend;
+	}
+
+	if (!wlr_udev_init(display, &state->udev)) {
+		wlr_log(L_ERROR, "Failed to start udev");
+		goto error_list;
+	}
+
+	state->fd = wlr_udev_find_gpu(&state->udev, state->session);
+	if (state->fd == -1) {
+		wlr_log(L_ERROR, "Failed to open DRM device");
+		goto error_udev;
+	}
+
+	struct wl_event_loop *event_loop = wl_display_get_event_loop(display);
+
+	state->drm_event = wl_event_loop_add_fd(event_loop, state->fd,
+		WL_EVENT_READABLE, wlr_drm_event, NULL);
+	if (!state->drm_event) {
+		wlr_log(L_ERROR, "Failed to create DRM event source");
+		goto error_fd;
+	}
+
+	// TODO: what is the difference between the per-output renderer and this
+	// one?
+	if (!wlr_drm_renderer_init(&state->renderer, state->fd)) {
+		wlr_log(L_ERROR, "Failed to initialize renderer");
+		goto error_event;
+	}
+
+	return backend;
+
+error_event:
+	wl_event_source_remove(state->drm_event);
+error_fd:
+	wlr_session_close_file(state->session, state->fd);
+error_udev:
+	wlr_udev_free(&state->udev);
+error_list:
+	list_free(state->outputs);
+error_backend:
+	free(state);
+	free(backend);
+	return NULL;
+}
diff --git a/backend/drm/drm.c b/backend/drm/drm.c
new file mode 100644
index 00000000..7cbd3e4a
--- /dev/null
+++ b/backend/drm/drm.c
@@ -0,0 +1,418 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <xf86drm.h>
+#include <xf86drmMode.h>
+#include <drm_mode.h>
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+#include <gbm.h>
+#include <GLES3/gl3.h>
+#include <wayland-server.h>
+
+#include "wayland.h"
+#include "backend.h"
+#include "backend/drm/backend.h"
+#include "backend/drm/drm.h"
+#include "common/log.h"
+
+static const char *conn_name[] = {
+	[DRM_MODE_CONNECTOR_Unknown]     = "Unknown",
+	[DRM_MODE_CONNECTOR_VGA]         = "VGA",
+	[DRM_MODE_CONNECTOR_DVII]        = "DVI-I",
+	[DRM_MODE_CONNECTOR_DVID]        = "DVI-D",
+	[DRM_MODE_CONNECTOR_DVIA]        = "DVI-A",
+	[DRM_MODE_CONNECTOR_Composite]   = "Composite",
+	[DRM_MODE_CONNECTOR_SVIDEO]      = "SVIDEO",
+	[DRM_MODE_CONNECTOR_LVDS]        = "LVDS",
+	[DRM_MODE_CONNECTOR_Component]   = "Component",
+	[DRM_MODE_CONNECTOR_9PinDIN]     = "DIN",
+	[DRM_MODE_CONNECTOR_DisplayPort] = "DP",
+	[DRM_MODE_CONNECTOR_HDMIA]       = "HDMI-A",
+	[DRM_MODE_CONNECTOR_HDMIB]       = "HDMI-B",
+	[DRM_MODE_CONNECTOR_TV]          = "TV",
+	[DRM_MODE_CONNECTOR_eDP]         = "eDP",
+	[DRM_MODE_CONNECTOR_VIRTUAL]     = "Virtual",
+	[DRM_MODE_CONNECTOR_DSI]         = "DSI",
+};
+
+bool wlr_drm_renderer_init(struct wlr_drm_renderer *renderer, int fd) {
+	renderer->gbm = gbm_create_device(fd);
+	if (!renderer->gbm) {
+		wlr_log(L_ERROR, "Failed to create GBM device: %s", strerror(errno));
+		return false;
+	}
+
+	if (!wlr_egl_init(&renderer->egl, EGL_PLATFORM_GBM_MESA, renderer->gbm)) {
+		gbm_device_destroy(renderer->gbm);
+		return false;
+	}
+
+	renderer->fd = fd;
+	return true;
+}
+
+void wlr_drm_renderer_free(struct wlr_drm_renderer *renderer) {
+	if (!renderer) {
+		return;
+	}
+	wlr_egl_free(&renderer->egl);
+	gbm_device_destroy(renderer->gbm);
+}
+
+static void free_fb(struct gbm_bo *bo, void *data) {
+	uint32_t *id = data;
+
+	if (id && *id) {
+		drmModeRmFB(gbm_bo_get_fd(bo), *id);
+	}
+
+	free(id);
+}
+
+static uint32_t get_fb_for_bo(int fd, struct gbm_bo *bo) {
+	uint32_t *id = gbm_bo_get_user_data(bo);
+
+	if (id) {
+		return *id;
+	}
+
+	id = calloc(1, sizeof *id);
+	if (!id) {
+		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		return 0;
+	}
+
+	drmModeAddFB(fd, gbm_bo_get_width(bo), gbm_bo_get_height(bo), 24, 32,
+		     gbm_bo_get_stride(bo), gbm_bo_get_handle(bo).u32, id);
+
+	gbm_bo_set_user_data(bo, id, free_fb);
+
+	return *id;
+}
+
+void wlr_drm_output_begin(struct wlr_output *output) {
+	struct wlr_output_state *_output = output->state;
+	struct wlr_drm_renderer *renderer = _output->renderer;
+	eglMakeCurrent(renderer->egl.display, _output->egl,
+			_output->egl, renderer->egl.context);
+}
+
+void wlr_drm_output_end(struct wlr_output *output) {
+	struct wlr_output_state *_output = output->state;
+	struct wlr_drm_renderer *renderer = _output->renderer;
+
+	eglSwapBuffers(renderer->egl.display, _output->egl);
+	struct gbm_bo *bo = gbm_surface_lock_front_buffer(_output->gbm);
+	uint32_t fb_id = get_fb_for_bo(renderer->fd, bo);
+	drmModePageFlip(renderer->fd, _output->crtc, fb_id, DRM_MODE_PAGE_FLIP_EVENT, _output);
+	gbm_surface_release_buffer(_output->gbm, bo);
+	_output->pageflip_pending = true;
+}
+
+static bool display_init_renderer(struct wlr_drm_renderer *renderer,
+	struct wlr_output_state *output) {
+	struct wlr_output_mode *mode = output->wlr_output->current_mode;
+	output->renderer = renderer;
+	output->gbm = gbm_surface_create(renderer->gbm, mode->width,
+		mode->height, GBM_FORMAT_XRGB8888, GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
+	if (!output->gbm) {
+		wlr_log(L_ERROR, "Failed to create GBM surface for %s: %s", output->name,
+			strerror(errno));
+		return false;
+	}
+
+	output->egl = wlr_egl_create_surface(&renderer->egl, output->gbm);
+	if (output->egl == EGL_NO_SURFACE) {
+		wlr_log(L_ERROR, "Failed to create EGL surface for %s", output->name);
+		return false;
+	}
+
+	// Render black frame
+	eglMakeCurrent(renderer->egl.display, output->egl, output->egl, renderer->egl.context);
+
+	glViewport(0, 0, output->width, output->height);
+	glClearColor(0.0, 0.0, 0.0, 1.0);
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	eglSwapBuffers(renderer->egl.display, output->egl);
+
+	struct gbm_bo *bo = gbm_surface_lock_front_buffer(output->gbm);
+	uint32_t fb_id = get_fb_for_bo(renderer->fd, bo);
+
+	drmModeSetCrtc(renderer->fd, output->crtc, fb_id, 0, 0,
+			&output->connector, 1, &mode->state->mode);
+	drmModePageFlip(renderer->fd, output->crtc, fb_id,
+			DRM_MODE_PAGE_FLIP_EVENT, output);
+
+	gbm_surface_release_buffer(output->gbm, bo);
+	return true;
+}
+
+static int find_id(const void *item, const void *cmp_to) {
+	const struct wlr_output_state *output = item;
+	const uint32_t *id = cmp_to;
+
+	if (output->connector < *id) {
+		return -1;
+	} else if (output->connector > *id) {
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+static bool wlr_drm_output_set_mode(struct wlr_output_state *output,
+		struct wlr_output_mode *mode) {
+	struct wlr_backend_state *state =
+		wl_container_of(output->renderer, state, renderer);
+
+	wlr_log(L_INFO, "Modesetting '%s' with '%ux%u@%u mHz'", output->name,
+			mode->width, mode->height, mode->refresh);
+
+	drmModeConnector *conn = drmModeGetConnector(state->fd, output->connector);
+	if (!conn) {
+		wlr_log(L_ERROR, "Failed to get DRM connector");
+		goto error;
+	}
+
+	if (conn->connection != DRM_MODE_CONNECTED || conn->count_modes == 0) {
+		wlr_log(L_ERROR, "%s is not connected", output->name);
+		goto error;
+	}
+
+	drmModeRes *res = drmModeGetResources(state->fd);
+	if (!res) {
+		wlr_log(L_ERROR, "Failed to get DRM resources");
+		goto error;
+	}
+
+	bool success = false;
+	for (int i = 0; !success && i < conn->count_encoders; ++i) {
+		drmModeEncoder *enc = drmModeGetEncoder(state->fd, conn->encoders[i]);
+		if (!enc) {
+			continue;
+		}
+
+		for (int j = 0; j < res->count_crtcs; ++j) {
+			if ((enc->possible_crtcs & (1 << j)) == 0) {
+				continue;
+			}
+
+			if ((state->taken_crtcs & (1 << j)) == 0) {
+				state->taken_crtcs |= 1 << j;
+				output->crtc = res->crtcs[j];
+				success = true;
+				break;
+			}
+		}
+		drmModeFreeEncoder(enc);
+	}
+
+	drmModeFreeResources(res);
+
+	if (!success) {
+		wlr_log(L_ERROR, "Failed to find CRTC for %s", output->name);
+		goto error;
+	}
+
+	output->state = DRM_OUTPUT_CONNECTED;
+	output->width = mode->width;
+	output->height = mode->height;
+	output->wlr_output->current_mode = mode;
+
+	if (!display_init_renderer(&state->renderer, output)) {
+		wlr_log(L_ERROR, "Failed to initalise renderer for %s", output->name);
+		goto error;
+	}
+
+	drmModeFreeConnector(conn);
+	return true;
+
+error:
+	wlr_drm_output_cleanup(output, false);
+	drmModeFreeConnector(conn);
+	return false;
+}
+
+static void wlr_drm_output_destroy(struct wlr_output_state *output) {
+	wlr_drm_output_cleanup(output, true);
+	wlr_drm_renderer_free(output->renderer);
+	free(output);
+}
+
+static struct wlr_output_impl output_impl = {
+	.set_mode = wlr_drm_output_set_mode,
+	.destroy = wlr_drm_output_destroy,
+};
+
+void wlr_drm_scan_connectors(struct wlr_backend_state *state) {
+	wlr_log(L_INFO, "Scanning DRM connectors");
+
+	drmModeRes *res = drmModeGetResources(state->fd);
+	if (!res) {
+		wlr_log(L_ERROR, "Failed to get DRM resources");
+		return;
+	}
+
+	for (int i = 0; i < res->count_connectors; ++i) {
+		uint32_t id = res->connectors[i];
+
+		drmModeConnector *conn = drmModeGetConnector(state->fd, id);
+		if (!conn) {
+			wlr_log(L_ERROR, "Failed to get DRM connector");
+			continue;
+		}
+
+		struct wlr_output_state *output;
+		struct wlr_output *wlr_output;
+		int index = list_seq_find(state->outputs, find_id, &id);
+
+		if (index == -1) {
+			output = calloc(1, sizeof(struct wlr_output_state));
+			if (!state) {
+				drmModeFreeConnector(conn);
+				wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+				return;
+			}
+			wlr_output = output->wlr_output = wlr_output_create(&output_impl, output);
+			if (!wlr_output) {
+				drmModeFreeConnector(conn);
+				wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+				return;
+			}
+
+			output->renderer = &state->renderer;
+			output->state = DRM_OUTPUT_DISCONNECTED;
+			output->connector = id;
+			// TODO: Populate more wlr_output fields
+			// TODO: Move this to wlr_output->name
+			snprintf(output->name, sizeof(output->name), "%s-%"PRIu32,
+				 conn_name[conn->connector_type],
+				 conn->connector_type_id);
+
+			drmModeEncoder *curr_enc = drmModeGetEncoder(state->fd, conn->encoder_id);
+			if (curr_enc) {
+				output->old_crtc = drmModeGetCrtc(state->fd, curr_enc->crtc_id);
+				free(curr_enc);
+			}
+
+			list_add(state->outputs, output);
+			wlr_log(L_INFO, "Found display '%s'", output->name);
+		} else {
+			output = state->outputs->items[index];
+			wlr_output = output->wlr_output;
+		}
+
+		// TODO: move state into wlr_output
+		if (output->state == DRM_OUTPUT_DISCONNECTED &&
+			conn->connection == DRM_MODE_CONNECTED) {
+
+			wlr_log(L_INFO, "'%s' connected", output->name);
+			wlr_log(L_INFO, "Detected modes:");
+
+			for (int i = 0; i < conn->count_modes; ++i) {
+				struct wlr_output_mode_state *_state = calloc(1,
+						sizeof(struct wlr_output_mode_state));
+				_state->mode = conn->modes[i];
+				struct wlr_output_mode *mode = calloc(1,
+						sizeof(struct wlr_output_mode));
+				mode->width = _state->mode.hdisplay;
+				// TODO: Calculate more accurate refresh rate
+				// TODO: Check that this refresh rate is mHz
+				mode->height = _state->mode.vdisplay;
+				mode->state = _state;
+
+				wlr_log(L_INFO, "  %"PRIu16"@%"PRIu16"@%"PRIu32,
+					_state->mode.hdisplay, _state->mode.vdisplay,
+					_state->mode.vrefresh);
+
+				list_add(wlr_output->modes, mode);
+			}
+
+			output->state = DRM_OUTPUT_NEEDS_MODESET;
+			wlr_log(L_INFO, "Sending modesetting signal for '%s'", output->name);
+			wl_signal_emit(&state->backend->events.output_add, wlr_output);
+		} else if (output->state == DRM_OUTPUT_CONNECTED &&
+			conn->connection != DRM_MODE_CONNECTED) {
+
+			wlr_log(L_INFO, "'%s' disconnected", output->name);
+			// TODO: Destroy
+			wlr_drm_output_cleanup(output, false);
+		}
+
+		drmModeFreeConnector(conn);
+	}
+
+	drmModeFreeResources(res);
+}
+
+static void page_flip_handler(int fd, unsigned seq,
+		unsigned tv_sec, unsigned tv_usec, void *user) {
+	struct wlr_output_state *output = user;
+	struct wlr_backend_state *state =
+		wl_container_of(output->renderer, state, renderer);
+
+	output->pageflip_pending = false;
+	if (output->state == DRM_OUTPUT_CONNECTED) {
+		wl_signal_emit(&output->wlr_output->events.frame, output->wlr_output);
+	}
+}
+
+int wlr_drm_event(int fd, uint32_t mask, void *data) {
+	drmEventContext event = {
+		.version = DRM_EVENT_CONTEXT_VERSION,
+		.page_flip_handler = page_flip_handler,
+	};
+
+	drmHandleEvent(fd, &event);
+	return 1;
+}
+
+static void restore_output(struct wlr_output_state *output, int fd) {
+	// Wait for any pending pageflips to finish
+	while (output->pageflip_pending) {
+		wlr_drm_event(fd, 0, NULL);
+	}
+
+	drmModeCrtc *crtc = output->old_crtc;
+	if (!crtc) {
+		return;
+	}
+
+	drmModeSetCrtc(fd, crtc->crtc_id, crtc->buffer_id, crtc->x, crtc->y,
+		&output->connector, 1, &crtc->mode);
+	drmModeFreeCrtc(crtc);
+}
+
+void wlr_drm_output_cleanup(struct wlr_output_state *output, bool restore) {
+	if (!output) {
+		return;
+	}
+
+	struct wlr_drm_renderer *renderer = output->renderer;
+	struct wlr_backend_state *state = wl_container_of(renderer, state, renderer);
+
+	switch (output->state) {
+	case DRM_OUTPUT_CONNECTED:
+		eglDestroySurface(renderer->egl.display, output->egl);
+		gbm_surface_destroy(output->gbm);
+		output->egl = EGL_NO_SURFACE;
+		output->gbm = NULL;
+		/* Fallthrough */
+	case DRM_OUTPUT_NEEDS_MODESET:
+		output->state = DRM_OUTPUT_DISCONNECTED;
+		if (restore) {
+			restore_output(output, renderer->fd);
+		}
+		wlr_log(L_INFO, "Emmiting destruction signal for '%s'", output->name);
+		wl_signal_emit(&state->backend->events.output_remove, output->wlr_output);
+		break;
+	case DRM_OUTPUT_DISCONNECTED:
+		break;
+	}
+	// TODO: free wlr_output
+}
diff --git a/backend/drm/udev.c b/backend/drm/udev.c
new file mode 100644
index 00000000..e5470157
--- /dev/null
+++ b/backend/drm/udev.c
@@ -0,0 +1,214 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include <libudev.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <xf86drm.h>
+#include <xf86drmMode.h>
+#include <wayland-server.h>
+
+#include <wlr/session.h>
+
+#include "backend.h"
+#include "backend/drm/backend.h"
+#include "backend/drm/udev.h"
+#include "backend/drm/drm.h"
+#include "common/log.h"
+
+/* Tests if 'path' is KMS compatible by trying to open it.
+ * It leaves the open device in *fd_out it it succeeds.
+ */
+static bool device_is_kms(struct wlr_session *restrict session,
+	const char *restrict path, int *restrict fd_out) {
+
+	int fd;
+
+	if (!path) {
+		return false;
+	}
+
+	fd = wlr_session_open_file(session, path);
+	if (fd < 0) {
+		return false;
+	}
+
+	drmModeRes *res = drmModeGetResources(fd);
+	if (!res) {
+		goto out_fd;
+	}
+
+	if (res->count_crtcs <= 0 || res->count_connectors <= 0 ||
+		res->count_encoders <= 0) {
+
+		goto out_res;
+	}
+
+	if (*fd_out >= 0) {
+		wlr_session_close_file(session, *fd_out);
+	}
+
+	*fd_out = fd;
+
+	drmModeFreeResources(res);
+	return true;
+
+out_res:
+	drmModeFreeResources(res);
+out_fd:
+	wlr_session_close_file(session, fd);
+	return false;
+}
+
+/* Tries to find the primary GPU by checking for the "boot_vga" attribute.
+ * If it's not found, it returns the first valid GPU it finds.
+ */
+int wlr_udev_find_gpu(struct wlr_udev *udev, struct wlr_session *session) {
+	struct udev_enumerate *en = udev_enumerate_new(udev->udev);
+	if (!en) {
+		wlr_log(L_ERROR, "Failed to create udev enumeration");
+		return -1;
+	}
+
+	udev_enumerate_add_match_subsystem(en, "drm");
+	udev_enumerate_add_match_sysname(en, "card[0-9]*");
+	udev_enumerate_scan_devices(en);
+
+	struct udev_list_entry *entry;
+	int fd = -1;
+	char *drm_path = NULL;
+
+	udev_list_entry_foreach(entry, udev_enumerate_get_list_entry(en)) {
+		bool is_boot_vga = false;
+
+		const char *path = udev_list_entry_get_name(entry);
+		struct udev_device *dev = udev_device_new_from_syspath(udev->udev, path);
+		if (!dev) {
+			continue;
+		}
+
+		/*
+		const char *seat = udev_device_get_property_value(dev, "ID_SEAT");
+		if (!seat)
+			seat = "seat0";
+		if (strcmp(session->seat, seat) != 0) {
+			udev_device_unref(dev);
+			continue;
+		}
+		*/
+
+		// This is owned by 'dev', so we don't need to free it
+		struct udev_device *pci =
+			udev_device_get_parent_with_subsystem_devtype(dev, "pci", NULL);
+
+		if (pci) {
+			const char *id = udev_device_get_sysattr_value(pci, "boot_vga");
+			if (id && strcmp(id, "1") == 0) {
+				is_boot_vga = true;
+			}
+		}
+
+		// We already have a valid GPU
+		if (!is_boot_vga && fd >= 0) {
+			udev_device_unref(dev);
+			continue;
+		}
+
+		path = udev_device_get_devnode(dev);
+		if (!device_is_kms(session, path, &fd)) {
+			udev_device_unref(dev);
+			continue;
+		}
+
+		free(drm_path);
+		drm_path = strdup(path);
+
+		udev_device_unref(dev);
+
+		// We've found the primary GPU
+		if (is_boot_vga) {
+			break;
+		}
+	}
+
+	udev_enumerate_unref(en);
+
+	udev->drm_path = drm_path;
+	return fd;
+}
+
+static int udev_event(int fd, uint32_t mask, void *data) {
+	struct wlr_udev *udev = data;
+	struct wlr_backend_state *state = wl_container_of(udev, state, udev);
+
+	struct udev_device *dev = udev_monitor_receive_device(udev->mon);
+	if (!dev) {
+		return 1;
+	}
+
+	const char *path = udev_device_get_devnode(dev);
+	if (!path || strcmp(path, udev->drm_path) != 0) {
+		goto out;
+	}
+
+	const char *action = udev_device_get_action(dev);
+	if (!action || strcmp(action, "change") != 0) {
+		goto out;
+	}
+
+	wlr_drm_scan_connectors(state);
+
+out:
+	udev_device_unref(dev);
+	return 1;
+}
+
+bool wlr_udev_init(struct wl_display *display, struct wlr_udev *udev) {
+	udev->udev = udev_new();
+	if (!udev->udev) {
+		wlr_log(L_ERROR, "Failed to create udev context");
+		return false;
+	}
+
+	udev->mon = udev_monitor_new_from_netlink(udev->udev, "udev");
+	if (!udev->mon) {
+		wlr_log(L_ERROR, "Failed to create udev monitor");
+		goto error_udev;
+	}
+
+	udev_monitor_filter_add_match_subsystem_devtype(udev->mon, "drm", NULL);
+	udev_monitor_enable_receiving(udev->mon);
+
+	struct wl_event_loop *event_loop = wl_display_get_event_loop(display);
+	int fd = udev_monitor_get_fd(udev->mon);
+
+	udev->event = wl_event_loop_add_fd(event_loop, fd, WL_EVENT_READABLE,
+		udev_event, udev);
+	if (!udev->event) {
+		wlr_log(L_ERROR, "Failed to create udev event source");
+		goto error_mon;
+	}
+
+	udev->drm_path = NULL;
+
+	return true;
+
+error_mon:
+	udev_monitor_unref(udev->mon);
+error_udev:
+	udev_unref(udev->udev);
+	return false;
+}
+
+void wlr_udev_free(struct wlr_udev *udev) {
+	if (!udev) {
+		return;
+	}
+
+	wl_event_source_remove(udev->event);
+
+	udev_monitor_unref(udev->mon);
+	udev_unref(udev->udev);
+	free(udev->drm_path);
+}