Merge branch 'optional_udev' into 'master'

[RFC] backend/session, backend/libinput: make udev optional

Closes #2257

See merge request wlroots/wlroots!3490

backend/libinput/backend.c

@@ -5,9 +5,16 @@
 #include <wlr/backend/interface.h>
 #include <wlr/backend/session.h>
 #include <wlr/util/log.h>
+#include <wlr/config.h>
 #include "backend/libinput.h"
 #include "util/signal.h"
 
+#if WLR_HAS_UDEV
+#include "backend/session/dev_udev.h"
+#endif
+
+#define NETLINK_BITMASK 4
+
 static struct wlr_libinput_backend *get_libinput_backend_from_backend(
 		struct wlr_backend *wlr_backend) {
 	assert(wlr_backend_is_libinput(wlr_backend));
@@ -86,15 +93,33 @@ static bool backend_start(struct wlr_backend *wlr_backend) {
 		get_libinput_backend_from_backend(wlr_backend);
 	wlr_log(WLR_DEBUG, "Starting libinput backend");
 
+#if WLR_HAS_UDEV
 	backend->libinput_context = libinput_udev_create_context(&libinput_impl,
-		backend, backend->session->udev);
+		backend, backend->session->dev->udev);
+#elif WLR_HAS_DEMI
+	backend->libinput_context = libinput_create_context(&libinput_impl, backend);
+#elif defined(__linux__)
+	backend->libinput_context = libinput_netlink_create_context(&libinput_impl,
+		backend, NETLINK_BITMASK);
+#else
+#error Unsupported platform
+#endif
 	if (!backend->libinput_context) {
 		wlr_log(WLR_ERROR, "Failed to create libinput context");
 		return false;
 	}
 
+#if WLR_HAS_UDEV
 	if (libinput_udev_assign_seat(backend->libinput_context,
 			backend->session->seat) != 0) {
+#elif WLR_HAS_DEMI
+	if (libinput_assign_seat(backend->libinput_context, backend->session->seat) != 0) {
+#elif defined(__linux__)
+	if (libinput_netlink_assign_seat(backend->libinput_context,
+			backend->session->seat) != 0) {
+#else
+#error Unsupported platform
+#endif
 		wlr_log(WLR_ERROR, "Failed to assign libinput seat");
 		return false;
 	}

backend/libinput/tablet_pad.c

@@ -5,9 +5,14 @@
 #include <stdlib.h>
 #include <wlr/interfaces/wlr_tablet_pad.h>
 #include <wlr/util/log.h>
+#include <wlr/config.h>
 #include "backend/libinput.h"
 #include "util/signal.h"
 
+#if WLR_HAS_UDEV
+#include <libudev.h>
+#endif
+
 const struct wlr_tablet_pad_impl libinput_tablet_pad_impl = {
 	.name = "libinput-tablet-pad",
 };
@@ -106,9 +111,11 @@ void init_device_tablet_pad(struct wlr_libinput_input_device *dev) {
 	wlr_tablet_pad->strip_count =
 		libinput_device_tablet_pad_get_num_strips(handle);
 
+#if WLR_HAS_UDEV
 	struct udev_device *udev = libinput_device_get_udev_device(handle);
 	char **dst = wl_array_add(&wlr_tablet_pad->paths, sizeof(char *));
 	*dst = strdup(udev_device_get_syspath(udev));
+#endif
 
 	int groups = libinput_device_tablet_pad_get_num_mode_groups(handle);
 	for (int i = 0; i < groups; ++i) {

backend/libinput/tablet_tool.c

@@ -5,9 +5,14 @@
 #include <stdlib.h>
 #include <wlr/interfaces/wlr_tablet_tool.h>
 #include <wlr/util/log.h>
+#include <wlr/config.h>
 #include "backend/libinput.h"
 #include "util/signal.h"
 
+#if WLR_HAS_UDEV
+#include <libudev.h>
+#endif
+
 struct tablet_tool {
 	struct wlr_tablet_tool wlr_tool;
 	struct libinput_tablet_tool *handle;
@@ -28,9 +33,11 @@ void init_device_tablet(struct wlr_libinput_input_device *dev) {
 	libinput_device_get_size(dev->handle, &wlr_tablet->width_mm,
 		&wlr_tablet->height_mm);
 
+#if WLR_HAS_UDEV
 	struct udev_device *udev = libinput_device_get_udev_device(dev->handle);
 	char **dst = wl_array_add(&wlr_tablet->paths, sizeof(char *));
 	*dst = strdup(udev_device_get_syspath(udev));
+#endif
 
 	wl_list_init(&dev->tablet_tools);
 }

backend/session/dev.c

@@ -0,0 +1,21 @@
+#define _POSIX_C_SOURCE 200809L
+#include <stdbool.h>
+#include <string.h>
+#include <xf86drm.h>
+#include "backend/session/dev.h"
+
+// TODO move to util?
+bool is_drm_card(const char *devname) {
+	const char prefix[] = DRM_PRIMARY_MINOR_NAME;
+	const char *name = strrchr(devname, '/');
+	name = name ? name + 1 : devname;
+	if (strncmp(name, prefix, strlen(prefix)) != 0) {
+		return false;
+	}
+	for (size_t i = strlen(prefix); name[i] != '\0'; i++) {
+		if (name[i] < '0' || name[i] > '9') {
+			return false;
+		}
+	}
+	return true;
+}

backend/session/dev_demi.c

@@ -0,0 +1,135 @@
+#define _POSIX_C_SOURCE 200809L
+#include <demi.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <time.h>
+#include <wayland-server-core.h>
+#include <wlr/backend/session.h>
+#include <wlr/config.h>
+#include <wlr/util/log.h>
+#include <xf86drm.h>
+#include "backend/session/session.h"
+#include "backend/session/dev.h"
+#include "backend/session/dev_demi.h"
+#include "util/signal.h"
+
+static int handle_event(int fd, uint32_t mask, void *data) {
+	struct wlr_session *session = data;
+
+	struct demi_event event;
+	if (demi_read(fd, &event) == -1) {
+		// TODO log
+		return 1;
+	}
+
+	const char *devname = event.de_devname;
+	enum demi_event_type event_type = event.de_type;
+
+	if (event_type == DEMI_UNKNOWN) {
+		// TODO log
+		return 1;
+	}
+
+	if (!is_drm_card(devname)) {
+		// TODO log
+		return 1;
+	}
+
+	char devnode[sizeof("/dev/") + sizeof(event.de_devname)];
+	snprintf(devnode, sizeof(devnode), "/dev/%s", devname);
+
+	wlr_log(WLR_DEBUG, "kernel event for %s (code %d)", devnode, event_type);
+
+	// TODO https://todo.sr.ht/~kennylevinsen/seatd/1
+	const char *seat = "seat0";
+	if (session->seat[0] != '\0' && strcmp(session->seat, seat) != 0) {
+		return 1;
+	}
+
+	if (event_type == DEMI_ATTACH) {
+		wlr_log(WLR_DEBUG, "DRM device %s added", devnode);
+		struct wlr_session_add_event event = {
+			.path = devnode,
+		};
+		wlr_signal_emit_safe(&session->events.add_drm_card, &event);
+	} else if (event_type == DEMI_CHANGE || event_type == DEMI_DETACH) {
+		struct stat st;
+		bool has_devnum = stat(devnode, &st) == 0;
+
+		struct wlr_device *dev;
+		wl_list_for_each(dev, &session->devices, link) {
+			if (has_devnum) {
+				if (dev->dev != st.st_rdev) {
+					continue;
+				}
+			} else {
+				if (strcmp(dev->devnode, devnode) != 0) {
+					continue;
+				}
+			}
+
+			if (event_type == DEMI_CHANGE) {
+				wlr_log(WLR_DEBUG, "DRM device %s changed", devnode);
+				// TODO
+				// struct wlr_device_change_event event = {0};
+				// read_udev_change_event(&event, udev_dev);
+				wlr_signal_emit_safe(&dev->events.change, NULL);
+			} else if (event_type == DEMI_DETACH) {
+				wlr_log(WLR_DEBUG, "DRM device %s removed", devnode);
+				wlr_signal_emit_safe(&dev->events.remove, NULL);
+			} else {
+				abort();
+			}
+			break;
+		}
+	}
+
+	return 1;
+}
+
+int dev_init(struct wlr_session *session, struct wl_display *disp) {
+	struct dev *dev = calloc(1, sizeof(*dev));
+	if (!dev) {
+		wlr_log_errno(WLR_ERROR, "Allocation failed");
+		return -1;
+	}
+
+	dev->fd = demi_init(DEMI_CLOEXEC | DEMI_NONBLOCK);
+	if (dev->fd == -1) {
+		wlr_log_errno(WLR_ERROR, "Failed to subscribe to kernel events");
+		goto error_dev;
+	}
+
+	struct wl_event_loop *event_loop = wl_display_get_event_loop(disp);
+
+	dev->event = wl_event_loop_add_fd(event_loop, dev->fd,
+		WL_EVENT_READABLE, handle_event, session);
+	if (!dev->event) {
+		wlr_log_errno(WLR_ERROR, "Failed to create gpu hotplugging event source");
+		goto error_fd;
+	}
+
+	session->dev = dev;
+	return 0;
+
+error_fd:
+	close(dev->fd);
+error_dev:
+	free(dev);
+	return -1;
+}
+
+void dev_finish(struct wlr_session *session) {
+	if (!session) {
+		return;
+	}
+
+	wl_event_source_remove(session->dev->event);
+	close(session->dev->fd);
+	free(session->dev);
+}

backend/session/dev_udev.c

@@ -0,0 +1,306 @@
+#define _POSIX_C_SOURCE 200809L
+#include <assert.h>
+#include <libudev.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <time.h>
+#include <wayland-server-core.h>
+#include <wlr/backend/session.h>
+#include <wlr/config.h>
+#include <wlr/util/log.h>
+#include <xf86drm.h>
+#include "backend/session/session.h"
+#include "backend/session/dev.h"
+#include "backend/session/dev_udev.h"
+#include "util/signal.h"
+
+#define WAIT_GPU_TIMEOUT 10000 // ms
+
+static void read_udev_change_event(struct wlr_device_change_event *event,
+		struct udev_device *udev_dev) {
+	const char *hotplug = udev_device_get_property_value(udev_dev, "HOTPLUG");
+	if (hotplug != NULL && strcmp(hotplug, "1") == 0) {
+		event->type = WLR_DEVICE_HOTPLUG;
+		struct wlr_device_hotplug_event *hotplug = &event->hotplug;
+
+		const char *connector =
+			udev_device_get_property_value(udev_dev, "CONNECTOR");
+		if (connector != NULL) {
+			hotplug->connector_id = strtoul(connector, NULL, 10);
+		}
+
+		const char *prop =
+			udev_device_get_property_value(udev_dev, "PROPERTY");
+		if (prop != NULL) {
+			hotplug->prop_id = strtoul(prop, NULL, 10);
+		}
+
+		return;
+	}
+
+	const char *lease = udev_device_get_property_value(udev_dev, "LEASE");
+	if (lease != NULL && strcmp(lease, "1") == 0) {
+		event->type = WLR_DEVICE_LEASE;
+		return;
+	}
+}
+
+static int handle_udev_event(int fd, uint32_t mask, void *data) {
+	struct wlr_session *session = data;
+
+	struct udev_device *udev_dev = udev_monitor_receive_device(session->dev->mon);
+	if (!udev_dev) {
+		return 1;
+	}
+
+	const char *sysname = udev_device_get_sysname(udev_dev);
+	const char *devnode = udev_device_get_devnode(udev_dev);
+	const char *action = udev_device_get_action(udev_dev);
+	wlr_log(WLR_DEBUG, "udev event for %s (%s)", sysname, action);
+
+	if (!is_drm_card(sysname) || !action || !devnode) {
+		goto out;
+	}
+
+	const char *seat = udev_device_get_property_value(udev_dev, "ID_SEAT");
+	if (!seat) {
+		seat = "seat0";
+	}
+	if (session->seat[0] != '\0' && strcmp(session->seat, seat) != 0) {
+		goto out;
+	}
+
+	if (strcmp(action, "add") == 0) {
+		wlr_log(WLR_DEBUG, "DRM device %s added", sysname);
+		struct wlr_session_add_event event = {
+			.path = devnode,
+		};
+		wlr_signal_emit_safe(&session->events.add_drm_card, &event);
+	} else if (strcmp(action, "change") == 0 || strcmp(action, "remove") == 0) {
+		dev_t devnum = udev_device_get_devnum(udev_dev);
+		struct wlr_device *dev;
+		wl_list_for_each(dev, &session->devices, link) {
+			if (dev->dev != devnum) {
+				continue;
+			}
+
+			if (strcmp(action, "change") == 0) {
+				wlr_log(WLR_DEBUG, "DRM device %s changed", sysname);
+				struct wlr_device_change_event event = {0};
+				read_udev_change_event(&event, udev_dev);
+				wlr_signal_emit_safe(&dev->events.change, &event);
+			} else if (strcmp(action, "remove") == 0) {
+				wlr_log(WLR_DEBUG, "DRM device %s removed", sysname);
+				wlr_signal_emit_safe(&dev->events.remove, NULL);
+			} else {
+				assert(0);
+			}
+			break;
+		}
+	}
+
+out:
+	udev_device_unref(udev_dev);
+	return 1;
+}
+
+int dev_init(struct wlr_session *session, struct wl_display *disp) {
+	struct dev *dev = calloc(1, sizeof(*dev));
+	if (!dev) {
+		wlr_log_errno(WLR_ERROR, "Allocation failed");
+		return -1;
+	}
+
+	dev->udev = udev_new();
+	if (!dev->udev) {
+		wlr_log_errno(WLR_ERROR, "Failed to create udev context");
+		goto error_dev;
+	}
+
+	dev->mon = udev_monitor_new_from_netlink(dev->udev, "udev");
+	if (!dev->mon) {
+		wlr_log_errno(WLR_ERROR, "Failed to create udev monitor");
+		goto error_udev;
+	}
+
+	udev_monitor_filter_add_match_subsystem_devtype(dev->mon, "drm", NULL);
+	udev_monitor_enable_receiving(dev->mon);
+
+	struct wl_event_loop *event_loop = wl_display_get_event_loop(disp);
+	int fd = udev_monitor_get_fd(dev->mon);
+
+	dev->udev_event = wl_event_loop_add_fd(event_loop, fd,
+		WL_EVENT_READABLE, handle_udev_event, session);
+	if (!dev->udev_event) {
+		wlr_log_errno(WLR_ERROR, "Failed to create udev event source");
+		goto error_mon;
+	}
+
+	session->dev = dev;
+	return 0;
+
+error_mon:
+	udev_monitor_unref(dev->mon);
+error_udev:
+	udev_unref(dev->udev);
+error_dev:
+	free(dev);
+	return -1;
+}
+
+void dev_finish(struct wlr_session *session) {
+	if (!session) {
+		return;
+	}
+
+	wl_event_source_remove(session->dev->udev_event);
+	udev_monitor_unref(session->dev->mon);
+	udev_unref(session->dev->udev);
+	free(session->dev);
+}
+
+static struct udev_enumerate *enumerate_drm_cards(struct udev *udev) {
+	struct udev_enumerate *en = udev_enumerate_new(udev);
+	if (!en) {
+		wlr_log(WLR_ERROR, "udev_enumerate_new failed");
+		return NULL;
+	}
+
+	udev_enumerate_add_match_subsystem(en, "drm");
+	udev_enumerate_add_match_sysname(en, DRM_PRIMARY_MINOR_NAME "[0-9]*");
+
+	if (udev_enumerate_scan_devices(en) != 0) {
+		wlr_log(WLR_ERROR, "udev_enumerate_scan_devices failed");
+		udev_enumerate_unref(en);
+		return NULL;
+	}
+
+	return en;
+}
+
+static uint64_t get_current_time_ms(void) {
+	struct timespec ts = {0};
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
+}
+
+struct find_gpus_add_handler {
+	bool added;
+	struct wl_listener listener;
+};
+
+static void find_gpus_handle_add(struct wl_listener *listener, void *data) {
+	struct find_gpus_add_handler *handler =
+		wl_container_of(listener, handler, listener);
+	handler->added = true;
+}
+
+/* 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.
+ */
+ssize_t dev_find_gpus(struct wlr_session *session,
+		size_t ret_len, struct wlr_device **ret) {
+	struct udev_enumerate *en = enumerate_drm_cards(session->dev->udev);
+	if (!en) {
+		return -1;
+	}
+
+	if (udev_enumerate_get_list_entry(en) == NULL) {
+		udev_enumerate_unref(en);
+		wlr_log(WLR_INFO, "Waiting for a DRM card device");
+
+		struct find_gpus_add_handler handler = {0};
+		handler.listener.notify = find_gpus_handle_add;
+		wl_signal_add(&session->events.add_drm_card, &handler.listener);
+
+		uint64_t started_at = get_current_time_ms();
+		uint64_t timeout = WAIT_GPU_TIMEOUT;
+		struct wl_event_loop *event_loop =
+			wl_display_get_event_loop(session->display);
+		while (!handler.added) {
+			int ret = wl_event_loop_dispatch(event_loop, (int)timeout);
+			if (ret < 0) {
+				wlr_log_errno(WLR_ERROR, "Failed to wait for DRM card device: "
+					"wl_event_loop_dispatch failed");
+				udev_enumerate_unref(en);
+				return -1;
+			}
+
+			uint64_t now = get_current_time_ms();
+			if (now >= started_at + WAIT_GPU_TIMEOUT) {
+				break;
+			}
+			timeout = started_at + WAIT_GPU_TIMEOUT - now;
+		}
+
+		wl_list_remove(&handler.listener.link);
+
+		en = enumerate_drm_cards(session->dev->udev);
+		if (!en) {
+			return -1;
+		}
+	}
+
+	struct udev_list_entry *entry;
+	size_t i = 0;
+
+	udev_list_entry_foreach(entry, udev_enumerate_get_list_entry(en)) {
+		if (i == ret_len) {
+			break;
+		}
+
+		bool is_boot_vga = false;
+
+		const char *path = udev_list_entry_get_name(entry);
+		struct udev_device *dev = udev_device_new_from_syspath(session->dev->udev, path);
+		if (!dev) {
+			continue;
+		}
+
+		const char *seat = udev_device_get_property_value(dev, "ID_SEAT");
+		if (!seat) {
+			seat = "seat0";
+		}
+		if (session->seat[0] && 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;
+			}
+		}
+
+		struct wlr_device *wlr_dev =
+			session_open_if_kms(session, udev_device_get_devnode(dev));
+		if (!wlr_dev) {
+			udev_device_unref(dev);
+			continue;
+		}
+
+		udev_device_unref(dev);
+
+		ret[i] = wlr_dev;
+		if (is_boot_vga) {
+			struct wlr_device *tmp = ret[0];
+			ret[0] = ret[i];
+			ret[i] = tmp;
+		}
+
+		++i;
+	}
+
+	udev_enumerate_unref(en);
+
+	return i;
+}

backend/session/meson.build

@@ -3,5 +3,29 @@ libseat = dependency('libseat',
 	fallback: 'seatd',
 	default_options: ['server=disabled', 'man-pages=disabled'],
 )
-wlr_files += files('session.c')
+wlr_files += files('session.c', 'dev.c')
 wlr_deps += libseat
+
+# libudev & libdemi
+
+if get_option('enum-backend') == 'auto'
+	udev = dependency('libudev', required: false)
+	demi = dependency('demi', required: false)
+	if udev.found()
+		wlr_files += files('dev_udev.c')
+		wlr_deps += udev
+		features += { 'udev': true }
+	elif demi.found()
+		wlr_files += files('dev_demi.c')
+		wlr_deps += demi
+		features += { 'demi': true }
+	endif
+elif get_option('enum-backend') == 'udev'
+	wlr_files += files('dev_udev.c')
+	wlr_deps += dependency('libudev')
+	features += { 'udev': true }
+elif get_option('enum-backend') == 'demi'
+	wlr_files += files('dev_demi.c')
+	wlr_deps += dependency('demi')
+	features += { 'demi': true }
+endif

backend/session/session.c

@@ -1,8 +1,5 @@
 #define _POSIX_C_SOURCE 200809L
-#include <assert.h>
-#include <libudev.h>
 #include <stdarg.h>
-#include <stddef.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -17,12 +14,11 @@
 #include <xf86drm.h>
 #include <xf86drmMode.h>
 #include "backend/session/session.h"
+#include "backend/session/dev.h"
 #include "util/signal.h"
 
 #include <libseat.h>
 
-#define WAIT_GPU_TIMEOUT 10000 // ms
-
 static void handle_enable_seat(struct libseat *seat, void *data) {
 	struct wlr_session *session = data;
 	session->active = true;
@@ -126,107 +122,6 @@ static void libseat_session_finish(struct wlr_session *session) {
 	session->libseat_event = NULL;
 }
 
-static bool is_drm_card(const char *sysname) {
-	const char prefix[] = DRM_PRIMARY_MINOR_NAME;
-	if (strncmp(sysname, prefix, strlen(prefix)) != 0) {
-		return false;
-	}
-	for (size_t i = strlen(prefix); sysname[i] != '\0'; i++) {
-		if (sysname[i] < '0' || sysname[i] > '9') {
-			return false;
-		}
-	}
-	return true;
-}
-
-static void read_udev_change_event(struct wlr_device_change_event *event,
-		struct udev_device *udev_dev) {
-	const char *hotplug = udev_device_get_property_value(udev_dev, "HOTPLUG");
-	if (hotplug != NULL && strcmp(hotplug, "1") == 0) {
-		event->type = WLR_DEVICE_HOTPLUG;
-		struct wlr_device_hotplug_event *hotplug = &event->hotplug;
-
-		const char *connector =
-			udev_device_get_property_value(udev_dev, "CONNECTOR");
-		if (connector != NULL) {
-			hotplug->connector_id = strtoul(connector, NULL, 10);
-		}
-
-		const char *prop =
-			udev_device_get_property_value(udev_dev, "PROPERTY");
-		if (prop != NULL) {
-			hotplug->prop_id = strtoul(prop, NULL, 10);
-		}
-
-		return;
-	}
-
-	const char *lease = udev_device_get_property_value(udev_dev, "LEASE");
-	if (lease != NULL && strcmp(lease, "1") == 0) {
-		event->type = WLR_DEVICE_LEASE;
-		return;
-	}
-}
-
-static int handle_udev_event(int fd, uint32_t mask, void *data) {
-	struct wlr_session *session = data;
-
-	struct udev_device *udev_dev = udev_monitor_receive_device(session->mon);
-	if (!udev_dev) {
-		return 1;
-	}
-
-	const char *sysname = udev_device_get_sysname(udev_dev);
-	const char *devnode = udev_device_get_devnode(udev_dev);
-	const char *action = udev_device_get_action(udev_dev);
-	wlr_log(WLR_DEBUG, "udev event for %s (%s)", sysname, action);
-
-	if (!is_drm_card(sysname) || !action || !devnode) {
-		goto out;
-	}
-
-	const char *seat = udev_device_get_property_value(udev_dev, "ID_SEAT");
-	if (!seat) {
-		seat = "seat0";
-	}
-	if (session->seat[0] != '\0' && strcmp(session->seat, seat) != 0) {
-		goto out;
-	}
-
-	if (strcmp(action, "add") == 0) {
-		wlr_log(WLR_DEBUG, "DRM device %s added", sysname);
-		struct wlr_session_add_event event = {
-			.path = devnode,
-		};
-		wlr_signal_emit_safe(&session->events.add_drm_card, &event);
-	} else if (strcmp(action, "change") == 0 || strcmp(action, "remove") == 0) {
-		dev_t devnum = udev_device_get_devnum(udev_dev);
-		struct wlr_device *dev;
-		wl_list_for_each(dev, &session->devices, link) {
-			if (dev->dev != devnum) {
-				continue;
-			}
-
-			if (strcmp(action, "change") == 0) {
-				wlr_log(WLR_DEBUG, "DRM device %s changed", sysname);
-				struct wlr_device_change_event event = {0};
-				read_udev_change_event(&event, udev_dev);
-				wlr_signal_emit_safe(&dev->events.change, &event);
-			} else if (strcmp(action, "remove") == 0) {
-				wlr_log(WLR_DEBUG, "DRM device %s removed", sysname);
-				wlr_signal_emit_safe(&dev->events.remove, NULL);
-			} else {
-				assert(0);
-			}
-			break;
-		}
-	}
-
-out:
-	udev_device_unref(udev_dev);
-	return 1;
-}
-
 static void handle_display_destroy(struct wl_listener *listener, void *data) {
 	struct wlr_session *session =
 		wl_container_of(listener, session, display_destroy);
@@ -250,30 +145,12 @@ struct wlr_session *wlr_session_create(struct wl_display *disp) {
 		goto error_open;
 	}
 
-	session->udev = udev_new();
-	if (!session->udev) {
-		wlr_log_errno(WLR_ERROR, "Failed to create udev context");
+#if WLR_HAS_UDEV || WLR_HAS_DEMI
+	if (dev_init(session, disp) == -1) {
+		wlr_log(WLR_ERROR, "Failed to initialize dev backend");
 		goto error_session;
 	}
-
-	session->mon = udev_monitor_new_from_netlink(session->udev, "udev");
-	if (!session->mon) {
-		wlr_log_errno(WLR_ERROR, "Failed to create udev monitor");
-		goto error_udev;
-	}
-
-	udev_monitor_filter_add_match_subsystem_devtype(session->mon, "drm", NULL);
-	udev_monitor_enable_receiving(session->mon);
-
-	struct wl_event_loop *event_loop = wl_display_get_event_loop(disp);
-	int fd = udev_monitor_get_fd(session->mon);
-
-	session->udev_event = wl_event_loop_add_fd(event_loop, fd,
-		WL_EVENT_READABLE, handle_udev_event, session);
-	if (!session->udev_event) {
-		wlr_log_errno(WLR_ERROR, "Failed to create udev event source");
-		goto error_mon;
-	}
+#endif
 
 	session->display = disp;
 
@@ -282,12 +159,10 @@ struct wlr_session *wlr_session_create(struct wl_display *disp) {
 
 	return session;
 
-error_mon:
-	udev_monitor_unref(session->mon);
-error_udev:
-	udev_unref(session->udev);
+#if WLR_HAS_UDEV || WLR_HAS_DEMI
 error_session:
 	libseat_session_finish(session);
+#endif
 error_open:
 	free(session);
 	return NULL;
@@ -301,9 +176,9 @@ void wlr_session_destroy(struct wlr_session *session) {
 	wlr_signal_emit_safe(&session->events.destroy, session);
 	wl_list_remove(&session->display_destroy.link);
 
-	wl_event_source_remove(session->udev_event);
-	udev_monitor_unref(session->mon);
-	udev_unref(session->udev);
+#if WLR_HAS_UDEV || WLR_HAS_DEMI
+	dev_finish(session);
+#endif
 
 	struct wlr_device *dev, *tmp_dev;
 	wl_list_for_each_safe(dev, tmp_dev, &session->devices, link) {
@@ -335,6 +210,12 @@ struct wlr_device *wlr_session_open_file(struct wlr_session *session,
 		goto error;
 	}
 
+	dev->devnode = strdup(path);
+	if (!dev->devnode) {
+		wlr_log_errno(WLR_ERROR, "Allocation failed");
+		goto error;
+	}
+
 	dev->fd = fd;
 	dev->dev = st.st_rdev;
 	dev->device_id = device_id;
@@ -358,6 +239,7 @@ void wlr_session_close_file(struct wlr_session *session,
 	}
 	close(dev->fd);
 	wl_list_remove(&dev->link);
+	free(dev->devnode);
 	free(dev);
 }
 
@@ -418,45 +300,6 @@ static ssize_t explicit_find_gpus(struct wlr_session *session,
 	return i;
 }
 
-static struct udev_enumerate *enumerate_drm_cards(struct udev *udev) {
-	struct udev_enumerate *en = udev_enumerate_new(udev);
-	if (!en) {
-		wlr_log(WLR_ERROR, "udev_enumerate_new failed");
-		return NULL;
-	}
-
-	udev_enumerate_add_match_subsystem(en, "drm");
-	udev_enumerate_add_match_sysname(en, DRM_PRIMARY_MINOR_NAME "[0-9]*");
-
-	if (udev_enumerate_scan_devices(en) != 0) {
-		wlr_log(WLR_ERROR, "udev_enumerate_scan_devices failed");
-		udev_enumerate_unref(en);
-		return NULL;
-	}
-
-	return en;
-}
-
-static uint64_t get_current_time_ms(void) {
-	struct timespec ts = {0};
-	clock_gettime(CLOCK_MONOTONIC, &ts);
-	return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
-}
-
-struct find_gpus_add_handler {
-	bool added;
-	struct wl_listener listener;
-};
-
-static void find_gpus_handle_add(struct wl_listener *listener, void *data) {
-	struct find_gpus_add_handler *handler =
-		wl_container_of(listener, handler, listener);
-	handler->added = true;
-}
-
-/* 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.
- */
 ssize_t wlr_session_find_gpus(struct wlr_session *session,
 		size_t ret_len, struct wlr_device **ret) {
 	const char *explicit = getenv("WLR_DRM_DEVICES");
@@ -464,103 +307,61 @@ ssize_t wlr_session_find_gpus(struct wlr_session *session,
 		return explicit_find_gpus(session, ret_len, ret, explicit);
 	}
 
-	struct udev_enumerate *en = enumerate_drm_cards(session->udev);
-	if (!en) {
+#if WLR_HAS_UDEV
+	return dev_find_gpus(session, ret_len, ret);
+#endif
+
+	int cnt = drmGetDevices2(0, NULL, 0);
+	if (cnt <= 0) {
+		return cnt == 0 ? 0 : -1;
+	}
+
+	drmDevicePtr *devs = calloc(cnt, sizeof(*devs));
+	if (!devs) {
+		wlr_log_errno(WLR_ERROR, "Allocation failed");
 		return -1;
 	}
 
-	if (udev_enumerate_get_list_entry(en) == NULL) {
-		udev_enumerate_unref(en);
-		wlr_log(WLR_INFO, "Waiting for a DRM card device");
-
-		struct find_gpus_add_handler handler = {0};
-		handler.listener.notify = find_gpus_handle_add;
-		wl_signal_add(&session->events.add_drm_card, &handler.listener);
-
-		uint64_t started_at = get_current_time_ms();
-		uint64_t timeout = WAIT_GPU_TIMEOUT;
-		struct wl_event_loop *event_loop =
-			wl_display_get_event_loop(session->display);
-		while (!handler.added) {
-			int ret = wl_event_loop_dispatch(event_loop, (int)timeout);
-			if (ret < 0) {
-				wlr_log_errno(WLR_ERROR, "Failed to wait for DRM card device: "
-					"wl_event_loop_dispatch failed");
-				udev_enumerate_unref(en);
-				return -1;
-			}
-
-			uint64_t now = get_current_time_ms();
-			if (now >= started_at + WAIT_GPU_TIMEOUT) {
-				break;
-			}
-			timeout = started_at + WAIT_GPU_TIMEOUT - now;
-		}
-
-		wl_list_remove(&handler.listener.link);
-
-		en = enumerate_drm_cards(session->udev);
-		if (!en) {
-			return -1;
-		}
+	cnt = drmGetDevices2(0, devs, cnt);
+	if (cnt <= 0) {
+		free(devs);
+		return cnt == 0 ? 0 : -1;
 	}
 
-	struct udev_list_entry *entry;
-	size_t i = 0;
+	ssize_t total = 0;
+	size_t max = (size_t)cnt > ret_len ? ret_len : (size_t)cnt;
 
-	udev_list_entry_foreach(entry, udev_enumerate_get_list_entry(en)) {
-		if (i == ret_len) {
-			break;
+	for (size_t i = 0; i < max; i++) {
+		if (!(devs[i]->available_nodes & (1 << DRM_NODE_PRIMARY))) {
+			continue;
 		}
 
+		// TODO
 		bool is_boot_vga = false;
 
-		const char *path = udev_list_entry_get_name(entry);
-		struct udev_device *dev = udev_device_new_from_syspath(session->udev, path);
-		if (!dev) {
+		// TODO https://todo.sr.ht/~kennylevinsen/seatd/1
+		const char *seat = "seat0";
+		if (session->seat[0] != '\0' && strcmp(session->seat, seat) != 0) {
 			continue;
 		}
 
-		const char *seat = udev_device_get_property_value(dev, "ID_SEAT");
-		if (!seat) {
-			seat = "seat0";
-		}
-		if (session->seat[0] && 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;
-			}
-		}
-
-		struct wlr_device *wlr_dev =
-			session_open_if_kms(session, udev_device_get_devnode(dev));
+		const char *devnode = devs[i]->nodes[DRM_NODE_PRIMARY];
+		struct wlr_device *wlr_dev = session_open_if_kms(session, devnode);
 		if (!wlr_dev) {
-			udev_device_unref(dev);
 			continue;
 		}
 
-		udev_device_unref(dev);
-
-		ret[i] = wlr_dev;
+		ret[total] = wlr_dev;
 		if (is_boot_vga) {
 			struct wlr_device *tmp = ret[0];
-			ret[0] = ret[i];
-			ret[i] = tmp;
+			ret[0] = ret[total];
+			ret[total] = tmp;
 		}
 
-		++i;
+		total++;
 	}
 
-	udev_enumerate_unref(en);
-
-	return i;
+	drmFreeDevices(devs, cnt);
+	free(devs);
+	return total;
 }

include/backend/session/dev.h

@@ -0,0 +1,16 @@
+#include <stdbool.h>
+#include <sys/types.h>
+#include <wlr/backend/session.h>
+#include <wayland-server-core.h>
+
+#ifndef BACKEND_SESSION_DEV_H
+#define BACKEND_SESSION_DEV_H
+
+int dev_init(struct wlr_session *session, struct wl_display *display);
+void dev_finish(struct wlr_session *session);
+
+ssize_t dev_find_gpus(struct wlr_session *session, size_t ret_len,
+		struct wlr_device **ret);
+
+bool is_drm_card(const char *devname);
+#endif

include/backend/session/dev_demi.h

@@ -0,0 +1,11 @@
+#include <wayland-server-core.h>
+
+#ifndef BACKEND_SESSION_DEV_DEMI_H
+#define BACKEND_SESSION_DEV_DEMI_H
+
+struct dev {
+	int fd;
+	struct wl_event_source *event;
+};
+
+#endif

include/backend/session/dev_udev.h

@@ -0,0 +1,13 @@
+#include <libudev.h>
+#include <wayland-server-core.h>
+
+#ifndef BACKEND_SESSION_DEV_UDEV_H
+#define BACKEND_SESSION_DEV_UDEV_H
+
+struct dev {
+	struct udev *udev;
+	struct udev_monitor *mon;
+	struct wl_event_source *udev_event;
+};
+
+#endif

include/wlr/backend/session.h

@@ -1,17 +1,18 @@
 #ifndef WLR_BACKEND_SESSION_H
 #define WLR_BACKEND_SESSION_H
 
-#include <libudev.h>
 #include <stdbool.h>
 #include <sys/types.h>
 #include <wayland-server-core.h>
 
 struct libseat;
+struct dev;
 
 struct wlr_device {
 	int fd;
 	int device_id;
 	dev_t dev;
+	char *devnode;
 	struct wl_list link;
 
 	struct {
@@ -34,9 +35,7 @@ struct wlr_session {
 	unsigned vtnr;
 	char seat[256];
 
-	struct udev *udev;
-	struct udev_monitor *mon;
-	struct wl_event_source *udev_event;
+	struct dev *dev;
 
 	struct libseat *seat_handle;
 	struct wl_event_source *libseat_event;

include/wlr/config.h.in

@@ -11,4 +11,7 @@
 
 #mesondefine WLR_HAS_XWAYLAND
 
+#mesondefine WLR_HAS_UDEV
+#mesondefine WLR_HAS_DEMI
+
 #endif

meson.build

@@ -92,6 +92,8 @@ features = {
 	'xwayland': false,
 	'gles2-renderer': false,
 	'vulkan-renderer': false,
+	'udev': false,
+	'demi': false,
 }
 internal_features = {
 	'xcb-errors': false,
@@ -127,7 +129,6 @@ drm = dependency('libdrm',
 )
 gbm = dependency('gbm', version: '>=17.1.0')
 xkbcommon = dependency('xkbcommon')
-udev = dependency('libudev')
 pixman = dependency('pixman-1')
 math = cc.find_library('m')
 rt = cc.find_library('rt')
@@ -138,7 +139,6 @@ wlr_deps = [
 	drm,
 	gbm,
 	xkbcommon,
-	udev,
 	pixman,
 	math,
 	rt,

meson_options.txt

@@ -4,3 +4,4 @@ option('examples', type: 'boolean', value: true, description: 'Build example app
 option('icon_directory', description: 'Location used to look for cursors (default: ${datadir}/icons)', type: 'string', value: '')
 option('renderers', type: 'array', choices: ['auto', 'gles2', 'vulkan'], value: ['auto'], description: 'Select built-in renderers')
 option('backends', type: 'array', choices: ['auto', 'drm', 'libinput', 'x11'], value: ['auto'], description: 'Select built-in backends')
+option('enum-backend', type: 'combo', choices: ['auto', 'disabled', 'udev', 'demi'], value: 'udev', description: 'Select device enumeration backend')