evdev: implement our evdev device dispatch as plugin

This makes event handling easier where plugins queue other event frames
per frame. Our initialization guarantees that our evdev code is alway
the last plugin in the series so in the no-plugin case we just pass on
to that.

The effective event flow is now:
    evdev.c -> plugin1 -> plugin2 -> evdev-plugin.c -> evdev.c
except that no plugins exist yet.

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1217>

meson.build

@@ -379,6 +379,7 @@ src_libinput = src_libfilter + [
 	'src/evdev.c',
 	'src/evdev-debounce.c',
 	'src/evdev-fallback.c',
+	'src/evdev-plugin.c',
 	'src/evdev-totem.c',
 	'src/evdev-middle-button.c',
 	'src/evdev-mt-touchpad.c',

src/evdev-plugin.c

@@ -0,0 +1,148 @@
+/*
+ * Copyright © 2025 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "config.h"
+
+#include "util-mem.h"
+#include <mtdev-plumbing.h>
+
+#include "evdev.h"
+#include "evdev-plugin.h"
+
+_unused_
+static inline void
+evdev_print_event(struct evdev_device *device,
+		  const struct evdev_event *e,
+		  uint64_t time_in_us)
+{
+	static uint32_t offset = 0;
+	static uint32_t last_time = 0;
+	uint32_t time = us2ms(time_in_us);
+
+	if (offset == 0) {
+		offset = time;
+		last_time = time - offset;
+	}
+
+	time -= offset;
+
+	switch (evdev_usage_enum(e->usage)) {
+	case EVDEV_SYN_REPORT:
+		evdev_log_debug(device,
+			  "%u.%03u ----------------- EV_SYN ----------------- +%ums\n",
+			  time / 1000,
+			  time % 1000,
+			  time - last_time);
+
+		last_time = time;
+		break;
+	case EVDEV_MSC_SERIAL:
+		evdev_log_debug(device,
+			"%u.%03u %-16s %-16s %#010x\n",
+			time / 1000,
+			time % 1000,
+			evdev_event_get_type_name(e),
+			evdev_event_get_code_name(e),
+			e->value);
+		break;
+	default:
+		evdev_log_debug(device,
+			  "%u.%03u %-16s %-20s %4d\n",
+			  time / 1000,
+			  time % 1000,
+			  evdev_event_get_type_name(e),
+			  evdev_event_get_code_name(e),
+			  e->value);
+		break;
+	}
+}
+
+static inline void
+evdev_process_event(struct evdev_device *device,
+		    struct evdev_event *e,
+		    uint64_t time)
+{
+	struct evdev_dispatch *dispatch = device->dispatch;
+
+#if EVENT_DEBUGGING
+	evdev_print_event(device, e, time);
+#endif
+
+	libinput_timer_flush(evdev_libinput_context(device), time);
+
+	dispatch->interface->process(dispatch, device, e, time);
+}
+
+static inline void
+evdev_device_dispatch_one(struct libinput_plugin *plugin,
+			  struct libinput_device *libinput_device,
+			  struct evdev_frame *frame)
+{
+	struct evdev_device *device = evdev_device(libinput_device);
+	uint64_t time = evdev_frame_get_time(frame);
+
+	size_t nevents;
+	struct evdev_event *events = evdev_frame_get_events(frame, &nevents);
+	for (size_t i = 0; i < nevents; i++) {
+		struct evdev_event *ev = &events[i];
+		if (!device->mtdev) {
+			evdev_process_event(device, ev, time);
+		} else {
+			struct input_event e = evdev_event_to_input_event(ev, time);
+			mtdev_put_event(device->mtdev, &e);
+			if (evdev_usage_eq(ev->usage, EVDEV_SYN_REPORT)) {
+				while (!mtdev_empty(device->mtdev)) {
+					struct input_event e;
+
+					mtdev_get_event(device->mtdev, &e);
+
+					uint64_t time;
+					struct evdev_event ev = evdev_event_from_input_event(&e, &time);
+					evdev_process_event(device, &ev, time);
+				}
+			}
+		}
+	}
+
+	/* Discard event to make the plugin system aware we're done */
+	evdev_frame_reset(frame);
+}
+
+static const struct libinput_plugin_interface interface = {
+	.run = NULL,
+	.destroy = NULL,
+	.device_new = NULL,
+	.device_ignored = NULL,
+	.device_added = NULL,
+	.device_removed = NULL,
+	.evdev_frame = evdev_device_dispatch_one,
+};
+
+void
+libinput_evdev_dispatch_plugin(struct libinput *libinput)
+{
+	_unref_(libinput_plugin) *p = libinput_plugin_new(libinput,
+							  "evdev",
+							  &interface,
+							  NULL);
+}

src/evdev-plugin.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright © 2025 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "config.h"
+
+#include "libinput.h"
+#include "libinput-plugin.h"
+
+void
+libinput_evdev_dispatch_plugin(struct libinput *libinput);

src/evdev.c

@@ -43,6 +43,7 @@
 #include "evdev-frame.h"
 #include "filter.h"
 #include "libinput-private.h"
+#include "libinput-plugin.h"
 #include "quirks.h"
 #include "util-input-event.h"
 #include "util-udev.h"
@@ -1032,108 +1033,14 @@ evdev_read_switch_reliability_prop(struct evdev_device *device)
 	return r;
 }
 
-_unused_
-static inline void
-evdev_print_event(struct evdev_device *device,
-		  const struct evdev_event *e,
-		  uint64_t time_in_us)
-{
-	static uint32_t offset = 0;
-	static uint32_t last_time = 0;
-	uint32_t time = us2ms(time_in_us);
-
-	if (offset == 0) {
-		offset = time;
-		last_time = time - offset;
-	}
-
-	time -= offset;
-
-	switch (evdev_usage_enum(e->usage)) {
-	case EVDEV_SYN_REPORT:
-		evdev_log_debug(device,
-			  "%u.%03u ----------------- EV_SYN ----------------- +%ums\n",
-			  time / 1000,
-			  time % 1000,
-			  time - last_time);
-
-		last_time = time;
-		break;
-	case EVDEV_MSC_SERIAL:
-		evdev_log_debug(device,
-			"%u.%03u %-16s %-16s %#010x\n",
-			time / 1000,
-			time % 1000,
-			evdev_event_get_type_name(e),
-			evdev_event_get_code_name(e),
-			e->value);
-		break;
-	default:
-		evdev_log_debug(device,
-			  "%u.%03u %-16s %-20s %4d\n",
-			  time / 1000,
-			  time % 1000,
-			  evdev_event_get_type_name(e),
-			  evdev_event_get_code_name(e),
-			  e->value);
-		break;
-	}
-}
-
-static inline void
-evdev_process_event(struct evdev_device *device,
-		    struct evdev_event *e,
-		    uint64_t time)
-{
-	struct evdev_dispatch *dispatch = device->dispatch;
-
-#if EVENT_DEBUGGING
-	evdev_print_event(device, e, time);
-#endif
-
-	libinput_timer_flush(evdev_libinput_context(device), time);
-
-	dispatch->interface->process(dispatch, device, e, time);
-}
-
-static inline void
-evdev_device_dispatch_one(struct evdev_device *device,
-			  struct evdev_event *ev,
-			  uint64_t time)
-{
-	if (!device->mtdev) {
-		evdev_process_event(device, ev, time);
-	} else {
-		struct input_event e = evdev_event_to_input_event(ev, time);
-		mtdev_put_event(device->mtdev, &e);
-		if (evdev_usage_eq(ev->usage, EVDEV_SYN_REPORT)) {
-			while (!mtdev_empty(device->mtdev)) {
-				struct input_event e;
-				mtdev_get_event(device->mtdev, &e);
-
-				uint64_t time;
-				struct evdev_event ev = evdev_event_from_input_event(&e, &time);
-				evdev_process_event(device, &ev, time);
-			}
-		}
-	}
-}
-
 static inline void
 evdev_device_dispatch_frame(struct libinput *libinput,
 			    struct evdev_device *device,
 			    struct evdev_frame *frame)
 {
-	size_t nevents;
-	struct evdev_event *events = evdev_frame_get_events(frame, &nevents);
-
 	libinput_plugin_system_notify_evdev_frame(&libinput->plugin_system,
 						  &device->base,
 						  frame);
-
-	for (size_t i = 0; i < nevents; i++) {
-		evdev_device_dispatch_one(device, &events[i], evdev_frame_get_time(frame));
-	}
 }
 
 static inline void

src/libinput-plugin-system.h

@@ -47,6 +47,10 @@ struct libinput_plugin_system {
 void
 libinput_plugin_system_init(struct libinput_plugin_system *system);
 
+void
+libinput_plugin_system_load_internal_plugins(struct libinput *libinput,
+					     struct libinput_plugin_system *system);
+
 void
 libinput_plugin_system_destroy(struct libinput_plugin_system *system);
 

src/libinput-plugin.c

@@ -33,9 +33,12 @@
 #include "libinput-plugin-system.h"
 
 #include "timer.h"
+
 #include "libinput-util.h"
 #include "libinput-private.h"
 
+#include "evdev-plugin.h"
+
 struct libinput_plugin {
 	struct libinput *libinput;
 	char *name;
@@ -352,6 +355,16 @@ libinput_plugin_system_init(struct libinput_plugin_system *system)
 	list_init(&system->removed_plugins);
 }
 
+void
+libinput_plugin_system_load_internal_plugins(struct libinput *libinput,
+					     struct libinput_plugin_system *system)
+{
+	/* Our own event dispatch is implemented as mini-plugin,
+	 * guarantee this one to always be last (and after any
+	 * other plugins have run so none of the devices are
+	 * actually connected to anything yet */
+	libinput_evdev_dispatch_plugin(libinput);
+}
 void
 libinput_plugin_system_destroy(struct libinput_plugin_system *system)
 {

src/path-seat.c

@@ -383,6 +383,9 @@ libinput_path_add_device(struct libinput *libinput,
 		return NULL;
 	}
 
+	libinput_plugin_system_load_internal_plugins(libinput,
+						     &libinput->plugin_system);
+
 	/* We cannot do this during path_create_context because the log
 	 * handler isn't set up there but we really want to log to the right
 	 * place if the quirks run into parser errors. So we have to do it

src/udev-seat.c

@@ -421,6 +421,9 @@ libinput_udev_assign_seat(struct libinput *libinput,
 	if (input->seat_id != NULL)
 		return -1;
 
+	libinput_plugin_system_load_internal_plugins(libinput,
+						     &libinput->plugin_system);
+
 	/* We cannot do this during udev_create_context because the log
 	 * handler isn't set up there but we really want to log to the right
 	 * place if the quirks run into parser errors. So we have to do it