Merge pull request #2 from ascent12/master

DRM backend + Session interface + EGL

31 files changed, 1814 insertions, 82 deletions

diff --git a/CMake/FindGBM.cmake b/CMake/FindGBM.cmake
new file mode 100644
index 00000000..85df1f7c
--- /dev/null
+++ b/CMake/FindGBM.cmake
@@ -0,0 +1,39 @@
+#.rst:
+# FindGBM
+# -------
+#
+# Find GBM library
+#
+# Try to find GBM library on UNIX systems. The following values are defined
+#
+# ::
+#
+#   GBM_FOUND         - True if gbm is available
+#   GBM_INCLUDE_DIRS  - Include directories for gbm
+#   GBM_LIBRARIES     - List of libraries for gbm
+#   GBM_DEFINITIONS   - List of definitions for gbm
+#
+#=============================================================================
+# Copyright (c) 2015 Jari Vetoniemi
+#
+# Distributed under the OSI-approved BSD License (the "License");
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+
+set_package_properties(GBM PROPERTIES
+   URL "http://www.mesa3d.org/"
+   DESCRIPTION "Generic buffer manager")
+
+find_package(PkgConfig)
+pkg_check_modules(PC_GBM QUIET gbm)
+find_library(GBM_LIBRARIES NAMES gbm HINTS ${PC_GBM_LIBRARY_DIRS})
+find_path(GBM_INCLUDE_DIRS gbm.h HINTS ${PC_GBM_INCLUDE_DIRS})
+
+set(GBM_DEFINITIONS ${PC_GBM_CFLAGS_OTHER})
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(GBM DEFAULT_MSG GBM_INCLUDE_DIRS GBM_LIBRARIES)
+mark_as_advanced(GBM_INCLUDE_DIRS GBM_LIBRARIES GBM_DEFINITIONS)
diff --git a/CMake/FindSystemd.cmake b/CMake/FindSystemd.cmake
new file mode 100644
index 00000000..09d60115
--- /dev/null
+++ b/CMake/FindSystemd.cmake
@@ -0,0 +1,40 @@
+#.rst:
+# FindSystemd
+# -------
+#
+# Find Systemd library
+#
+# Try to find Systemd library on UNIX systems. The following values are defined
+#
+# ::
+#
+#   SYSTEMD_FOUND         - True if Systemd is available
+#   SYSTEMD_INCLUDE_DIRS  - Include directories for Systemd
+#   SYSTEMD_LIBRARIES     - List of libraries for Systemd
+#   SYSTEMD_DEFINITIONS   - List of definitions for Systemd
+#
+#=============================================================================
+# Copyright (c) 2015 Jari Vetoniemi
+#
+# Distributed under the OSI-approved BSD License (the "License");
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+
+include(FeatureSummary)
+set_package_properties(Systemd PROPERTIES
+   URL "http://freedesktop.org/wiki/Software/systemd/"
+   DESCRIPTION "System and Service Manager")
+
+find_package(PkgConfig)
+pkg_check_modules(PC_SYSTEMD QUIET libsystemd)
+find_library(SYSTEMD_LIBRARIES NAMES systemd ${PC_SYSTEMD_LIBRARY_DIRS})
+find_path(SYSTEMD_INCLUDE_DIRS systemd/sd-login.h HINTS ${PC_SYSTEMD_INCLUDE_DIRS})
+
+set(SYSTEMD_DEFINITIONS ${PC_SYSTEMD_CFLAGS_OTHER})
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(SYSTEMD DEFAULT_MSG SYSTEMD_INCLUDE_DIRS SYSTEMD_LIBRARIES)
+mark_as_advanced(SYSTEMD_INCLUDE_DIRS SYSTEMD_LIBRARIES SYSTEMD_DEFINITIONS)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index dd4d9969..616a8911 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -48,9 +48,10 @@ find_package(WaylandProtocols REQUIRED)
 find_package(EGL REQUIRED)
 find_package(GLESv2 REQUIRED)
 find_package(DRM REQUIRED)
+find_package(GBM REQUIRED)
 find_package(LibInput REQUIRED)
-find_package(Udev)
-find_package(Dbus)
+find_package(Udev REQUIRED)
+find_package(Systemd)
 
 include(Wayland)
 include(Manpage)
@@ -60,5 +61,6 @@ include_directories(include)
 add_subdirectory(backend)
 add_subdirectory(common)
 add_subdirectory(wayland)
+add_subdirectory(session)
 
 add_subdirectory(example)
diff --git a/backend/CMakeLists.txt b/backend/CMakeLists.txt
index 830a2158..fc1793cf 100644
--- a/backend/CMakeLists.txt
+++ b/backend/CMakeLists.txt
@@ -1,17 +1,30 @@
 include_directories(
 	${PROTOCOLS_INCLUDE_DIRS}
 	${WAYLAND_INCLUDE_DIR}
+	${DRM_INCLUDE_DIRS}
 )
 
 add_library(wlr-backend
-    wayland/backend.c
-    wayland/registry.c
-    wayland/wl_seat.c
-    wayland/wl_output.c
+    #wayland/backend.c
+    #wayland/registry.c
+    #wayland/wl_seat.c
+    #wayland/wl_output.c
+    drm/backend.c
+    drm/drm.c
+    drm/udev.c
+    backend.c
+    egl.c
 )
 
 target_link_libraries(wlr-backend
     wlr-common
     wlr-wayland
     ${WAYLAND_LIBRARIES}
+    ${DRM_LIBRARIES}
+    ${GBM_LIBRARIES}
+    ${GLESv2_LIBRARIES}
+    ${EGL_LIBRARIES}
+    ${SYSTEMD_LIBRARIES}
+    ${UDEV_LIBRARIES}
+    ${GBM_LIBRARIES}
 )
diff --git a/backend/backend.c b/backend/backend.c
new file mode 100644
index 00000000..753bb3ae
--- /dev/null
+++ b/backend/backend.c
@@ -0,0 +1,36 @@
+#include <wayland-server.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include "common/log.h"
+#include "backend.h"
+
+struct wlr_backend *wlr_backend_create(const struct wlr_backend_impl *impl,
+		struct wlr_backend_state *state) {
+	struct wlr_backend *backend = calloc(1, sizeof(struct wlr_backend));
+	if (!backend) {
+		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		return NULL;
+	}
+	backend->state = state;
+	backend->impl = impl;
+	wl_signal_init(&backend->events.output_add);
+	wl_signal_init(&backend->events.output_remove);
+	wl_signal_init(&backend->events.keyboard_add);
+	wl_signal_init(&backend->events.keyboard_remove);
+	wl_signal_init(&backend->events.pointer_add);
+	wl_signal_init(&backend->events.pointer_remove);
+	wl_signal_init(&backend->events.touch_add);
+	wl_signal_init(&backend->events.touch_remove);
+	return backend;
+}
+
+bool wlr_backend_init(struct wlr_backend *backend) {
+	return backend->impl->init(backend->state);
+}
+
+void wlr_backend_destroy(struct wlr_backend *backend) {
+	backend->impl->destroy(backend->state);
+	// TODO: free outputs
+	free(backend);
+}
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);
+}
diff --git a/backend/egl.c b/backend/egl.c
new file mode 100644
index 00000000..2aac25b7
--- /dev/null
+++ b/backend/egl.c
@@ -0,0 +1,178 @@
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+#include <GLES3/gl3.h>
+#include <gbm.h> // GBM_FORMAT_XRGB8888
+
+#include "backend/egl.h"
+#include "common/log.h"
+
+static const char *egl_error(void) {
+	switch (eglGetError()) {
+	case EGL_SUCCESS:
+		return "Success";
+	case EGL_NOT_INITIALIZED:
+		return "Not initialized";
+	case EGL_BAD_ACCESS:
+		return "Bad access";
+	case EGL_BAD_ALLOC:
+		return "Bad alloc";
+	case EGL_BAD_ATTRIBUTE:
+		return "Bad attribute";
+	case EGL_BAD_CONTEXT:
+		return "Bad Context";
+	case EGL_BAD_CONFIG:
+		return "Bad Config";
+	case EGL_BAD_CURRENT_SURFACE:
+		return "Bad current surface";
+	case EGL_BAD_DISPLAY:
+		return "Bad display";
+	case EGL_BAD_SURFACE:
+		return "Bad surface";
+	case EGL_BAD_MATCH:
+		return "Bad match";
+	case EGL_BAD_PARAMETER:
+		return "Bad parameter";
+	case EGL_BAD_NATIVE_PIXMAP:
+		return "Bad native pixmap";
+	case EGL_BAD_NATIVE_WINDOW:
+		return "Bad native window";
+	case EGL_CONTEXT_LOST:
+		return "Context lost";
+	default:
+		return "Unknown";
+	}
+}
+
+// EGL extensions
+PFNEGLGETPLATFORMDISPLAYEXTPROC get_platform_display;
+PFNEGLCREATEPLATFORMWINDOWSURFACEEXTPROC create_platform_window_surface;
+
+static bool egl_exts() {
+	get_platform_display = (PFNEGLGETPLATFORMDISPLAYEXTPROC)
+		eglGetProcAddress("eglGetPlatformDisplayEXT");
+
+	if (!get_platform_display) {
+		wlr_log(L_ERROR, "Failed to load EGL extension 'eglGetPlatformDisplayEXT'");
+		return false;
+	}
+
+	create_platform_window_surface = (PFNEGLCREATEPLATFORMWINDOWSURFACEEXTPROC)
+		eglGetProcAddress("eglCreatePlatformWindowSurfaceEXT");
+
+	if (!get_platform_display) {
+		wlr_log(L_ERROR,
+			"Failed to load EGL extension 'eglCreatePlatformWindowSurfaceEXT'");
+		return false;
+	}
+
+	return true;
+}
+
+static bool egl_get_config(EGLDisplay disp, EGLConfig *out) {
+	EGLint count = 0, matched = 0, ret;
+
+	ret = eglGetConfigs(disp, NULL, 0, &count);
+	if (ret == EGL_FALSE || count == 0) {
+		return false;
+	}
+
+	EGLConfig configs[count];
+
+	ret = eglChooseConfig(disp, NULL, configs, count, &matched);
+	if (ret == EGL_FALSE) {
+		return false;
+	}
+
+	for (int i = 0; i < matched; ++i) {
+		EGLint gbm_format;
+
+		if (!eglGetConfigAttrib(disp,
+					configs[i],
+					EGL_NATIVE_VISUAL_ID,
+					&gbm_format)) {
+			continue;
+		}
+
+		// XXX: Is GBM_FORMAT_XRGB8888 what we want?
+		// I don't know if this works for wl_displays.
+		if (gbm_format == GBM_FORMAT_XRGB8888) {
+			*out = configs[i];
+			return true;
+		}
+	}
+
+	return false;
+}
+
+
+bool wlr_egl_init(struct wlr_egl *egl, EGLenum platform, void *display) {
+	if (!egl_exts()) {
+		return false;
+	}
+	
+	if (eglBindAPI(EGL_OPENGL_ES_API) == EGL_FALSE) {
+		wlr_log(L_ERROR, "Failed to bind to the OpenGL ES API: %s", egl_error());
+		goto error;
+	}
+
+	egl->display = get_platform_display(platform, display, NULL);
+	if (egl->display == EGL_NO_DISPLAY) {
+		wlr_log(L_ERROR, "Failed to create EGL display: %s", egl_error());
+		goto error;
+	}
+
+	EGLint major, minor;
+	if (eglInitialize(egl->display, &major, &minor) == EGL_FALSE) {
+		wlr_log(L_ERROR, "Failed to initialize EGL: %s", egl_error());
+		goto error;
+	}
+
+	if (!egl_get_config(egl->display, &egl->config)) {
+		wlr_log(L_ERROR, "Failed to get EGL config");
+		goto error;
+	}
+
+	static const EGLint attribs[] = {EGL_CONTEXT_CLIENT_VERSION, 3, EGL_NONE};
+
+	egl->context = eglCreateContext(egl->display, egl->config,
+		EGL_NO_CONTEXT, attribs);
+
+	if (egl->context == EGL_NO_CONTEXT) {
+		wlr_log(L_ERROR, "Failed to create EGL context: %s", egl_error());
+		goto error;
+	}
+
+	eglMakeCurrent(egl->display, EGL_NO_SURFACE, EGL_NO_SURFACE, egl->context);
+	wlr_log(L_INFO, "Using EGL %d.%d", (int)major, (int)minor);
+	wlr_log(L_INFO, "Supported EGL extensions: %s", eglQueryString(egl->display,
+		EGL_EXTENSIONS));
+	wlr_log(L_INFO, "Using %s", glGetString(GL_VERSION));
+	wlr_log(L_INFO, "Supported OpenGL ES extensions: %s", glGetString(GL_EXTENSIONS));
+
+	return true;
+
+error:
+	eglTerminate(egl->display);
+	eglReleaseThread();
+	eglMakeCurrent(EGL_NO_DISPLAY, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+
+	return false;
+}
+
+void wlr_egl_free(struct wlr_egl *egl) {
+	eglDestroyContext(egl->display, egl->context);
+	eglTerminate(egl->display);
+	eglReleaseThread();
+	eglMakeCurrent(EGL_NO_DISPLAY, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);	
+}
+
+EGLSurface wlr_egl_create_surface(struct wlr_egl *egl, void *window) {
+	EGLSurface surf = create_platform_window_surface(egl->display, egl->config,
+		window, NULL);
+	if (surf == EGL_NO_SURFACE) {
+		wlr_log(L_ERROR, "Failed to create EGL surface: %s", egl_error());
+		return EGL_NO_SURFACE;
+	}
+
+	return surf;
+}
diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
index 73768393..f619b97f 100644
--- a/example/CMakeLists.txt
+++ b/example/CMakeLists.txt
@@ -1,7 +1,12 @@
+include_directories(
+	${DRM_INCLUDE_DIRS}
+)
+
 add_executable(example
     main.c
 )
 
 target_link_libraries(example
     wlr-backend
+    wlr-session
 )
diff --git a/example/main.c b/example/main.c
index 4240b9e3..2c168d98 100644
--- a/example/main.c
+++ b/example/main.c
@@ -1,19 +1,133 @@
-#define _POSIX_C_SOURCE 200112L
+#define _POSIX_C_SOURCE 199309L
+#include <stdio.h>
 #include <stdlib.h>
-#include <wlr/backend.h>
-#include <wlr/backend/wayland.h>
+#include <time.h>
 #include <wayland-server.h>
+#include <GLES3/gl3.h>
+#include <wlr/backend/drm.h>
+#include <wlr/session.h>
+#include <wlr/common/list.h>
 
-int main(int argc, char **argv) {
-	// TODO: Move this stuff to a wlr backend selector function
-	char *_wl_display = getenv("WAYLAND_DISPLAY");
-	if (_wl_display) {
-		unsetenv("WAYLAND_DISPLAY");
-		setenv("_WAYLAND_DISPLAY", _wl_display, 1);
+struct state {
+	float color[3];
+	int dec;
+	struct timespec last_frame;
+	struct wl_listener output_add;
+	struct wl_listener output_remove;
+	list_t *outputs;
+};
+
+struct output_state {
+	struct wlr_output *output;
+	struct state *state;
+	struct wl_listener frame;
+};
+
+void output_frame(struct wl_listener *listener, void *data) {
+	struct wlr_output *output = data;
+	struct output_state *ostate = wl_container_of(
+			listener, ostate, frame);
+	struct state *s = ostate->state;
+
+	struct timespec now;
+	clock_gettime(CLOCK_MONOTONIC, &now);
+
+	long ms = (now.tv_sec - s->last_frame.tv_sec) * 1000 +
+		(now.tv_nsec - s->last_frame.tv_nsec) / 1000000;
+	int inc = (s->dec + 1) % 3;
+
+	s->color[inc] += ms / 2000.0f;
+	s->color[s->dec] -= ms / 2000.0f;
+
+	if (s->color[s->dec] < 0.0f) {
+		s->color[inc] = 1.0f;
+		s->color[s->dec] = 0.0f;
+
+		s->dec = inc;
+	}
+
+	s->last_frame = now;
+
+	wlr_drm_output_begin(output);
+
+	glClearColor(s->color[0], s->color[1], s->color[2], 1.0);
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	wlr_drm_output_end(output);
+}
+
+void output_add(struct wl_listener *listener, void *data) {
+	struct wlr_output *output = data;
+	struct state *state = wl_container_of(listener, state, output_add);
+	fprintf(stderr, "Output '%s' added\n", output->name);
+	wlr_output_set_mode(output, output->modes->items[0]);
+	struct output_state *ostate = calloc(1, sizeof(struct output_state));
+	ostate->output = output;
+	ostate->state = state;
+	ostate->frame.notify = output_frame;
+	wl_list_init(&ostate->frame.link);
+	wl_signal_add(&output->events.frame, &ostate->frame);
+	list_add(state->outputs, ostate);
+}
+
+void output_remove(struct wl_listener *listener, void *data) {
+	struct wlr_output *output = data;
+	fprintf(stderr, "Output '%s' removed\n", output->name);
+	// TODO: remove signal from state->output_frame
+}
+
+int timer_done(void *data) {
+	*(bool *)data = true;
+	return 1;
+}
+
+int main() {
+	if (getenv("DISPLAY")) {
+		fprintf(stderr, "Detected that X is running. Run this in its own virtual terminal.\n");
+		return 1;
+	} else if (getenv("WAYLAND_DISPLAY")) {
+		fprintf(stderr, "Detected that Wayland is running. Run this in its own virtual terminal.\n");
+		return 1;
+	}
+
+	struct state state = {
+		.color = { 1.0, 0.0, 0.0 },
+		.dec = 0,
+		.output_add = { .notify = output_add },
+		.output_remove = { .notify = output_remove },
+		.outputs = list_create(),
+	};
+
+	wl_list_init(&state.output_add.link);
+	wl_list_init(&state.output_remove.link);
+	clock_gettime(CLOCK_MONOTONIC, &state.last_frame);
+
+	struct wl_display *display = wl_display_create();
+	struct wl_event_loop *event_loop = wl_display_get_event_loop(display);
+
+	struct wlr_session *session = wlr_session_start();
+	if (!session) {
+		return 1;
+	}
+
+	struct wlr_backend *wlr = wlr_drm_backend_create(display, session);
+	wl_signal_add(&wlr->events.output_add, &state.output_add);
+	wl_signal_add(&wlr->events.output_remove, &state.output_remove);
+	if (!wlr || !wlr_backend_init(wlr)) {
+		return 1;
+	}
+
+	bool done = false;
+	struct wl_event_source *timer = wl_event_loop_add_timer(event_loop,
+		timer_done, &done);
+
+	wl_event_source_timer_update(timer, 5000);
+
+	while (!done) {
+		wl_event_loop_dispatch(event_loop, 0);
 	}
-	struct wl_display *wl_display = wl_display_create();
-	struct wlr_wl_backend *backend = wlr_wl_backend_init(wl_display, 1);
-	wlr_wl_backend_free(backend);
-	wl_display_destroy(wl_display);
-	return 0;
+
+	wl_event_source_remove(timer);
+	wlr_backend_destroy(wlr);
+	wl_display_destroy(display);
 }
diff --git a/include/backend.h b/include/backend.h
new file mode 100644
index 00000000..d42c6f17
--- /dev/null
+++ b/include/backend.h
@@ -0,0 +1,17 @@
+#ifndef _WLR_BACKEND_INTERNAL_H
+#define _WLR_BACKEND_INTERNAL_H
+
+#include <stdbool.h>
+#include <wlr/backend.h>
+
+struct wlr_backend_state;
+
+struct wlr_backend_impl {
+	bool (*init)(struct wlr_backend_state *state);
+	void (*destroy)(struct wlr_backend_state *state);
+};
+
+struct wlr_backend *wlr_backend_create(const struct wlr_backend_impl *impl,
+		struct wlr_backend_state *state);
+
+#endif
diff --git a/include/backend/drm/backend.h b/include/backend/drm/backend.h
new file mode 100644
index 00000000..0c725ccb
--- /dev/null
+++ b/include/backend/drm/backend.h
@@ -0,0 +1,34 @@
+#ifndef DRM_BACKEND_H
+#define DRM_BACKEND_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <EGL/egl.h>
+#include <gbm.h>
+#include <libudev.h>
+#include <wayland-server.h>
+
+#include <wlr/session.h>
+#include <wlr/common/list.h>
+#include <wlr/backend/drm.h>
+
+#include "backend.h"
+#include "udev.h"
+#include "event.h"
+#include "drm.h"
+
+struct wlr_backend_state {
+	int fd;
+
+	struct wlr_backend *backend;
+	struct wl_event_source *drm_event;
+
+	uint32_t taken_crtcs;
+	list_t *outputs;
+
+	struct wlr_drm_renderer renderer;
+	struct wlr_session *session;
+	struct wlr_udev udev;
+};
+
+#endif
diff --git a/include/backend/drm/drm.h b/include/backend/drm/drm.h
new file mode 100644
index 00000000..4b42aa68
--- /dev/null
+++ b/include/backend/drm/drm.h
@@ -0,0 +1,58 @@
+#ifndef DRM_H
+#define DRM_H
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <xf86drmMode.h>
+#include <EGL/egl.h>
+#include <gbm.h>
+
+#include "backend/egl.h"
+#include "backend.h"
+
+struct wlr_drm_renderer {
+	int fd;
+	struct gbm_device *gbm;
+	struct wlr_egl egl;
+};
+
+bool wlr_drm_renderer_init(struct wlr_drm_renderer *renderer, int fd);
+void wlr_drm_renderer_free(struct wlr_drm_renderer *renderer);
+
+enum wlr_drm_output_state {
+	DRM_OUTPUT_DISCONNECTED,
+	DRM_OUTPUT_NEEDS_MODESET,
+	DRM_OUTPUT_CONNECTED,
+};
+
+struct wlr_output_mode_state {
+	struct wlr_wl_output_mode *wlr_mode;
+	drmModeModeInfo mode;
+};
+
+struct wlr_output_state {
+	struct wlr_output *wlr_output;
+	enum wlr_drm_output_state state;
+	uint32_t connector;
+	char name[16];
+
+	uint32_t width;
+	uint32_t height;
+
+	uint32_t crtc;
+	drmModeCrtc *old_crtc;
+
+	struct wlr_drm_renderer *renderer;
+	struct gbm_surface *gbm;
+	EGLSurface *egl;
+
+	bool pageflip_pending;
+	bool cleanup;
+};
+
+void wlr_drm_output_cleanup(struct wlr_output_state *output, bool restore);
+
+void wlr_drm_scan_connectors(struct wlr_backend_state *state);
+int wlr_drm_event(int fd, uint32_t mask, void *data);
+
+#endif
diff --git a/include/backend/drm/udev.h b/include/backend/drm/udev.h
new file mode 100644
index 00000000..99c2c403
--- /dev/null
+++ b/include/backend/drm/udev.h
@@ -0,0 +1,24 @@
+#ifndef UDEV_H
+#define UDEV_H
+
+#include <libudev.h>
+
+#include <wlr/session.h>
+#include <wayland-server.h>
+
+struct wlr_udev {
+	struct udev *udev;
+	struct udev_monitor *mon;
+	char *drm_path;
+
+	struct wl_event_source *event;
+};
+
+struct wlr_drm_backend;
+bool wlr_udev_init(struct wl_display *display, struct wlr_udev *udev);
+void wlr_udev_free(struct wlr_udev *udev);
+int wlr_udev_find_gpu(struct wlr_udev *udev, struct wlr_session *session);
+
+void wlr_udev_event(struct wlr_drm_backend *backend);
+
+#endif
diff --git a/include/backend/egl.h b/include/backend/egl.h
new file mode 100644
index 00000000..8cef36b7
--- /dev/null
+++ b/include/backend/egl.h
@@ -0,0 +1,17 @@
+#ifndef WLR_BACKEND_EGL_H
+#define WLR_BACKEND_EGL_H
+
+#include <EGL/egl.h>
+#include <stdbool.h>
+
+struct wlr_egl {
+	EGLDisplay display;
+	EGLConfig config;
+	EGLContext context;
+};
+
+bool wlr_egl_init(struct wlr_egl *egl, EGLenum platform, void *display);
+void wlr_egl_free(struct wlr_egl *egl);
+EGLSurface wlr_egl_create_surface(struct wlr_egl *egl, void *window);
+
+#endif
diff --git a/include/session/interface.h b/include/session/interface.h
new file mode 100644
index 00000000..a815718f
--- /dev/null
+++ b/include/session/interface.h
@@ -0,0 +1,21 @@
+#ifndef WLR_SESSION_INTERFACE_H
+#define WLR_SESSION_INTERFACE_H
+
+struct wlr_session;
+
+struct session_interface {
+	struct wlr_session *(*start)(void);
+	void (*finish)(struct wlr_session *session);
+	int (*open)(struct wlr_session *restrict session,
+		const char *restrict path);
+	void (*close)(struct wlr_session *session, int fd);
+};
+
+struct wlr_session {
+	struct session_interface iface;
+};
+
+extern const struct session_interface session_logind_iface;
+extern const struct session_interface session_direct_iface;
+
+#endif
diff --git a/include/wayland.h b/include/wayland.h
new file mode 100644
index 00000000..68817936
--- /dev/null
+++ b/include/wayland.h
@@ -0,0 +1,18 @@
+#ifndef _WLR_WAYLAND_INTERNAL_H
+#define _WLR_WAYLAND_INTERNAL_H
+
+#include <wayland-server.h>
+#include <wlr/wayland.h>
+#include <stdbool.h>
+
+struct wlr_output_impl {
+	bool (*set_mode)(struct wlr_output_state *state, struct wlr_output_mode *mode);
+	void (*destroy)(struct wlr_output_state *state);
+};
+
+struct wlr_output *wlr_output_create(struct wlr_output_impl *impl,
+		struct wlr_output_state *state);
+
+void wlr_output_free(struct wlr_output *output);
+
+#endif
diff --git a/include/wlr/backend.h b/include/wlr/backend.h
index 527efa05..b424c29f 100644
--- a/include/wlr/backend.h
+++ b/include/wlr/backend.h
@@ -1,7 +1,29 @@
 #ifndef _WLR_BACKEND_H
 #define _WLR_BACKEND_H
 
-struct wlr_backend *wlr_backend_init();
-void wlr_backend_free(struct wlr_backend *backend);
+#include <wayland-server.h>
+
+struct wlr_backend_impl;
+struct wlr_backend_state;
+
+struct wlr_backend {
+	const struct wlr_backend_impl *impl;
+	struct wlr_backend_state *state;
+
+	struct {
+		struct wl_signal output_add;
+		struct wl_signal output_remove;
+		struct wl_signal keyboard_add;
+		struct wl_signal keyboard_remove;
+		struct wl_signal pointer_add;
+		struct wl_signal pointer_remove;
+		struct wl_signal touch_add;
+		struct wl_signal touch_remove;
+	} events;
+};
+
+struct wlr_backend *wlr_backend_autocreate();
+bool wlr_backend_init(struct wlr_backend *backend);
+void wlr_backend_destroy(struct wlr_backend *backend);
 
 #endif
diff --git a/include/wlr/backend/drm.h b/include/wlr/backend/drm.h
new file mode 100644
index 00000000..2d9bf879
--- /dev/null
+++ b/include/wlr/backend/drm.h
@@ -0,0 +1,16 @@
+#ifndef WLR_BACKEND_DRM_H
+#define WLR_BACKEND_DRM_H
+
+#include <wayland-server.h>
+#include <wlr/session.h>
+#include <wlr/backend.h>
+#include <xf86drmMode.h> // drmModeModeInfo
+#include <wlr/wayland.h>
+
+struct wlr_backend *wlr_drm_backend_create(struct wl_display *display,
+	struct wlr_session *session);
+
+void wlr_drm_output_begin(struct wlr_output *out);
+void wlr_drm_output_end(struct wlr_output *out);
+
+#endif
diff --git a/include/wlr/common/log.h b/include/wlr/common/log.h
index 5b4d5a53..079f989a 100644
--- a/include/wlr/common/log.h
+++ b/include/wlr/common/log.h
@@ -1,6 +1,7 @@
 #ifndef _WLR_COMMON_LOG_H
 #define _WLR_COMMON_LOG_H
 #include <stdbool.h>
+#include <stdarg.h>
 
 typedef enum {
 	L_SILENT = 0,
diff --git a/include/wlr/session.h b/include/wlr/session.h
new file mode 100644
index 00000000..cf04f1da
--- /dev/null
+++ b/include/wlr/session.h
@@ -0,0 +1,12 @@
+#ifndef WLR_SESSION_H
+#define WLR_SESSION_H
+
+struct wlr_session;
+
+struct wlr_session *wlr_session_start(void);
+void wlr_session_finish(struct wlr_session *session);
+int wlr_session_open_file(struct wlr_session *restrict session,
+	const char *restrict path);
+void wlr_session_close_file(struct wlr_session *session, int fd);
+
+#endif
diff --git a/include/wlr/wayland.h b/include/wlr/wayland.h
index bbbd2457..158acc33 100644
--- a/include/wlr/wayland.h
+++ b/include/wlr/wayland.h
@@ -3,26 +3,26 @@
 
 #include <wayland-server.h>
 #include <wlr/common/list.h>
+#include <stdbool.h>
 
-struct wlr_wl_seat {
-	struct wl_seat *wl_seat;
-	uint32_t capabilities;
-	char *name;
-	list_t *keyboards;
-	list_t *pointers;
-};
-
-void wlr_wl_seat_free(struct wlr_wl_seat *seat);
+struct wlr_output_mode_state;
 
-struct wlr_wl_output_mode {
+struct wlr_output_mode {
+	struct wlr_output_mode_state *state;
 	uint32_t flags; // enum wl_output_mode
 	int32_t width, height;
 	int32_t refresh; // mHz
 };
 
-struct wlr_wl_output {
-	struct wl_output *wl_output;
+struct wlr_output_impl;
+struct wlr_output_state;
+
+struct wlr_output {
+	const struct wlr_output_impl *impl;
+	struct wlr_output_state *state;
+
 	uint32_t flags;
+	char *name;
 	char *make;
 	char *model;
 	uint32_t scale;
@@ -30,20 +30,15 @@ struct wlr_wl_output {
 	int32_t phys_width, phys_height; // mm
 	int32_t subpixel; // enum wl_output_subpixel
 	int32_t transform; // enum wl_output_transform
-	list_t *modes;
-	struct wlr_wl_output_mode *current_mode;
-};
 
-void wlr_wl_output_free(struct wlr_wl_output *output);
+	list_t *modes;
+	struct wlr_output_mode *current_mode;
 
-struct wlr_wl_keyboard {
-	struct wl_keyboard *wl_keyboard;
+	struct {
+		struct wl_signal frame;
+	} events;
 };
 
-struct wlr_wl_pointer {
-	struct wl_pointer *wl_pointer;
-	struct wl_surface *current_surface;
-	wl_fixed_t x, y;
-};
+bool wlr_output_set_mode(struct wlr_output *output, struct wlr_output_mode *mode);
 
 #endif
diff --git a/session/CMakeLists.txt b/session/CMakeLists.txt
new file mode 100644
index 00000000..bd83068b
--- /dev/null
+++ b/session/CMakeLists.txt
@@ -0,0 +1,25 @@
+include_directories(
+	${WAYLAND_INCLUDE_DIR}
+)
+
+set(sources
+    session.c
+    direct.c
+)
+
+set(libs
+    wlr-common
+    ${WAYLAND_LIBRARIES}
+)
+
+if (SYSTEMD_FOUND)
+    add_definitions(${SYSTEMD_DEFINITIONS})
+    include_directories(${SYSTEMD_INCLUDE_DIRS})
+
+    add_definitions(-DHAS_SYSTEMD)
+    list(APPEND sources logind.c)
+    list(APPEND libs ${SYSTEMD_LIBRARIES})
+endif ()
+
+add_library(wlr-session ${sources})
+target_link_libraries(wlr-session ${libs})
diff --git a/session/direct.c b/session/direct.c
new file mode 100644
index 00000000..08a9b617
--- /dev/null
+++ b/session/direct.c
@@ -0,0 +1,50 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <wayland-server.h>
+
+#include "session/interface.h"
+#include "common/log.h"
+
+struct direct_session {
+	struct wlr_session base;
+};
+
+static int direct_session_open(struct wlr_session *restrict base,
+	const char *restrict path) {
+	return open(path, O_RDWR | O_CLOEXEC);
+}
+
+static void direct_session_close(struct wlr_session *base, int fd) {
+	close(fd);
+}
+
+static void direct_session_finish(struct wlr_session *base) {
+	struct direct_session *session = wl_container_of(base, session, base);
+
+	free(session);
+}
+
+static struct wlr_session *direct_session_start(void) {
+	struct direct_session *session = calloc(1, sizeof(*session));
+	if (!session) {
+		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		return NULL;
+	}
+
+	wlr_log(L_INFO, "Successfully loaded direct session");
+
+	session->base.iface = session_direct_iface;
+	return &session->base;
+}
+
+const struct session_interface session_direct_iface = {
+	.start = direct_session_start,
+	.finish = direct_session_finish,
+	.open = direct_session_open,
+	.close = direct_session_close,
+};
diff --git a/session/logind.c b/session/logind.c
new file mode 100644
index 00000000..052c7454
--- /dev/null
+++ b/session/logind.c
@@ -0,0 +1,223 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <systemd/sd-bus.h>
+#include <systemd/sd-login.h>
+#include <unistd.h>
+#include <sys/sysmacros.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <wayland-server.h>
+
+#include "session/interface.h"
+#include "common/log.h"
+
+struct logind_session {
+	struct wlr_session base;
+
+	sd_bus *bus;
+
+	char *id;
+	char *path;
+	char *seat;
+};
+
+static int logind_take_device(struct wlr_session *restrict base,
+	const char *restrict path) {
+
+	struct logind_session *session = wl_container_of(base, session, base);
+
+	int ret;
+	int fd = -1;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	struct stat st;
+	if (stat(path, &st) < 0) {
+		wlr_log(L_ERROR, "Failed to stat '%s'", path);
+		return -1;
+	}
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "TakeDevice",
+		&error, &msg, "uu", major(st.st_rdev), minor(st.st_rdev));
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to take device '%s': %s", path, error.message);
+		goto error;
+	}
+
+	int paused = 0;
+	ret = sd_bus_message_read(msg, "hb", &fd, &paused);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to parse DBus response for '%s': %s",
+			path, strerror(-ret));
+		goto error;
+	}
+
+	// The original fd seem to be closed when the message is freed
+	// so we just clone it.
+	fd = fcntl(fd, F_DUPFD_CLOEXEC, 0);
+	if (fd == -1) {
+		wlr_log(L_ERROR, "Failed to clone file descriptor for '%s': %s",
+			path, strerror(errno));
+		goto error;
+	}
+
+error:
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+	return fd;
+}
+
+static void logind_release_device(struct wlr_session *base, int fd) {
+	struct logind_session *session = wl_container_of(base, session, base);
+
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	struct stat st;
+	if (fstat(fd, &st) < 0) {
+		wlr_log(L_ERROR, "Failed to stat device '%d'", fd);
+		return;
+	}
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "ReleaseDevice",
+		&error, &msg, "uu", major(st.st_rdev), minor(st.st_rdev));
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to release device '%d'", fd);
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+}
+
+static bool session_activate(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "Activate",
+		&error, &msg, "");
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to activate session");
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+	return ret >= 0;
+}
+
+static bool take_control(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "TakeControl",
+		&error, &msg, "b", false);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to take control of session");
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+	return ret >= 0;
+}
+
+static void release_control(struct logind_session *session) {
+	int ret;
+	sd_bus_message *msg = NULL;
+	sd_bus_error error = SD_BUS_ERROR_NULL;
+
+	ret = sd_bus_call_method(session->bus, "org.freedesktop.login1",
+		session->path, "org.freedesktop.login1.Session", "ReleaseControl",
+		&error, &msg, "");
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to release control of session");
+	}
+
+	sd_bus_error_free(&error);
+	sd_bus_message_unref(msg);
+}
+
+static void logind_session_finish(struct wlr_session *base) {
+	struct logind_session *session = wl_container_of(base, session, base);
+
+	release_control(session);
+
+	sd_bus_unref(session->bus);
+	free(session->id);
+	free(session->path);
+	free(session->seat);
+	free(session);
+}
+
+static struct wlr_session *logind_session_start(void) {
+	int ret;
+	struct logind_session *session = calloc(1, sizeof(*session));
+	if (!session) {
+		wlr_log(L_ERROR, "Allocation failed: %s", strerror(errno));
+		return NULL;
+	}
+
+	ret = sd_pid_get_session(getpid(), &session->id);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to get session id: %s", strerror(-ret));
+		goto error;
+	}
+
+	ret = sd_session_get_seat(session->id, &session->seat);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to get seat id: %s", strerror(-ret));
+		goto error;
+	}
+
+	const char *fmt = "/org/freedesktop/login1/session/%s";
+	int len = snprintf(NULL, 0, fmt, session->id);
+
+	session->path = malloc(len + 1);
+	if (!session->path)
+		goto error;
+
+	sprintf(session->path, fmt, session->id);
+
+	ret = sd_bus_default_system(&session->bus);
+	if (ret < 0) {
+		wlr_log(L_ERROR, "Failed to open DBus connection: %s", strerror(-ret));
+		goto error;
+	}
+
+	if (!session_activate(session))
+		goto error_bus;
+
+	if (!take_control(session))
+		goto error_bus;
+
+	wlr_log(L_INFO, "Successfully loaded logind session");
+
+	session->base.iface = session_logind_iface;
+	return &session->base;
+
+error_bus:
+	sd_bus_unref(session->bus);
+
+error:
+	free(session->path);
+	free(session->id);
+	free(session->seat);
+	return NULL;
+}
+
+const struct session_interface session_logind_iface = {
+	.start = logind_session_start,
+	.finish = logind_session_finish,
+	.open = logind_take_device,
+	.close = logind_release_device,
+};
diff --git a/session/session.c b/session/session.c
new file mode 100644
index 00000000..0562dbf7
--- /dev/null
+++ b/session/session.c
@@ -0,0 +1,42 @@
+#include <stddef.h>
+
+#include <wlr/session.h>
+#include <stdarg.h>
+#include "common/log.h"
+#include "session/interface.h"
+
+static const struct session_interface *ifaces[] = {
+#ifdef HAS_SYSTEMD
+	&session_logind_iface,
+#endif
+	&session_direct_iface,
+	NULL,
+};
+
+struct wlr_session *wlr_session_start(void) {
+	const struct session_interface **iter;
+
+	for (iter = ifaces; *iter; ++iter) {
+		struct wlr_session *session = (*iter)->start();
+		if (session) {
+			return session;
+		}
+	}
+
+	wlr_log(L_ERROR, "Failed to load session backend");
+	return NULL;
+}
+
+void wlr_session_finish(struct wlr_session *session) {
+	session->iface.finish(session);
+};
+
+int wlr_session_open_file(struct wlr_session *restrict session,
+	const char *restrict path) {
+
+	return session->iface.open(session, path);
+}
+
+void wlr_session_close_file(struct wlr_session *session, int fd) {
+	session->iface.close(session, fd);
+}
diff --git a/wayland/CMakeLists.txt b/wayland/CMakeLists.txt
index be4a00de..675a7bd2 100644
--- a/wayland/CMakeLists.txt
+++ b/wayland/CMakeLists.txt
@@ -4,8 +4,7 @@ include_directories(
 )
 
 add_library(wlr-wayland
-    types/wlr_wl_seat.c
-    types/wlr_wl_output.c
+    types/wlr_output.c
 )
 
 target_link_libraries(wlr-wayland
diff --git a/wayland/types/wlr_output.c b/wayland/types/wlr_output.c
new file mode 100644
index 00000000..bc093c00
--- /dev/null
+++ b/wayland/types/wlr_output.c
@@ -0,0 +1,31 @@
+#include <stdlib.h>
+#include <wayland-server.h>
+#include "wlr/wayland.h"
+#include "wlr/common/list.h"
+#include "wayland.h"
+
+struct wlr_output *wlr_output_create(struct wlr_output_impl *impl,
+		struct wlr_output_state *state) {
+	struct wlr_output *output = calloc(1, sizeof(struct wlr_output));
+	output->impl = impl;
+	output->state = state;
+	output->modes = list_create();
+	wl_signal_init(&output->events.frame);
+	return output;
+}
+
+void wlr_output_free(struct wlr_output *output) {
+	if (!output) return;
+	if (output->make) free(output->make);
+	if (output->model) free(output->model);
+	for (size_t i = 0; output->modes && i < output->modes->length; ++i) {
+		free(output->modes->items[i]);
+	}
+	list_free(output->modes);
+	output->impl->destroy(output->state);
+	free(output);
+}
+
+bool wlr_output_set_mode(struct wlr_output *output, struct wlr_output_mode *mode) {
+	return output->impl->set_mode(output->state, mode);
+}
diff --git a/wayland/types/wlr_wl_output.c b/wayland/types/wlr_wl_output.c
deleted file mode 100644
index 32aaf070..00000000
--- a/wayland/types/wlr_wl_output.c
+++ /dev/null
@@ -1,16 +0,0 @@
-#include <stdlib.h>
-#include <wayland-client.h>
-#include "wlr/wayland.h"
-#include "wlr/common/list.h"
-
-void wlr_wl_output_free(struct wlr_wl_output *output) {
-	if (!output) return;
-	if (output->wl_output) wl_output_destroy(output->wl_output);
-	if (output->make) free(output->make);
-	if (output->model) free(output->model);
-	for (size_t i = 0; output->modes && i < output->modes->length; ++i) {
-		free(output->modes->items[i]);
-	}
-	list_free(output->modes);
-	free(output);
-}
diff --git a/wayland/types/wlr_wl_seat.c b/wayland/types/wlr_wl_seat.c
deleted file mode 100644
index a5ef3853..00000000
--- a/wayland/types/wlr_wl_seat.c
+++ /dev/null
@@ -1,19 +0,0 @@
-#include <stdlib.h>
-#include <wayland-client.h>
-#include "wlr/wayland.h"
-#include "wlr/common/list.h"
-
-void wlr_wl_seat_free(struct wlr_wl_seat *seat) {
-	if (!seat) return;
-	if (seat->wl_seat) wl_seat_destroy(seat->wl_seat);
-	if (seat->name) free(seat->name);
-	if (seat->keyboards) {
-		// TODO: free children
-		list_free(seat->keyboards);
-	}
-	if (seat->pointers) {
-		// TODO: free children
-		list_free(seat->keyboards);
-	}
-	free(seat);
-}