terminal: add input interface

The idev-interface provides input drivers for all libsystemd-terminal
based applications. It is split into 4 main objects:
    idev_context: The context object tracks global state of the input
                  interface. This will include data like system-keymaps,
                  xkb contexts and more.
    idev_session: A session serves as controller for a set of devices.
                  Each session on an idev-context is independent of each
                  other. The session is also the main notification object.
                  All events raised via idev are reported through the
                  session interface. Apart of that, the session is a
                  pretty dumb object that just contains devices.
    idev_element: Elements provide real hardware in the idev stack. For
                  each hardware device, one element is added. Elements
                  have no knowledge of higher-level device types, they
                  only provide raw input data to the upper levels. For
                  example, each evdev device is represented by a different
                  element in an idev session.
     idev_device: Devices are objects that the application deals with. An
                  application is usually not interested in elements (and
                  those are hidden to applications), instead, they want
                  high-level input devices like keyboard, touchpads, mice
                  and more. Device are the high-level interface provided
                  by idev. Each device might be fed by a set of elements.
                  Elements drive the device. If elements are removed,
                  devices are destroyed. If elements are added, suitable
                  devices are created.

Applications should monitor the system for sessions and hardware devices.
For each session they want to operate on, they create an idev_session
object and add hardware to that object. The idev interface requires the
application to monitor the system (preferably via sysview_*, but not
required) for hardware devices. Whenever hardware is added to the idev
session, new devices *might* be created. The relationship between hardware
and high-level idev-devices is hidden in the idev-session and not exposed.

Internally, the idev elements and devices are virtual objects. Each real
hardware and device type inherits those virtual objects and provides real
elements and devices. Those types will be added in follow-up commits.

Data flow from hardware to the application is done via idev_*_feed()
functions. Data flow from applications to hardware is done via
idev_*_feedback() functions. Feedback is usually used for LEDs, FF and
similar operations.

4 files changed, 888 insertions, 0 deletions

diff --git a/Makefile.am b/Makefile.am
index 3a263f8c17..82f474e20e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2971,6 +2971,9 @@ libsystemd_terminal_la_CFLAGS = \
 	$(AM_CFLAGS)
 
 libsystemd_terminal_la_SOURCES = \
+	src/libsystemd-terminal/idev.h \
+	src/libsystemd-terminal/idev-internal.h \
+	src/libsystemd-terminal/idev.c \
 	src/libsystemd-terminal/sysview.h \
 	src/libsystemd-terminal/sysview-internal.h \
 	src/libsystemd-terminal/sysview.c \
diff --git a/src/libsystemd-terminal/idev-internal.h b/src/libsystemd-terminal/idev-internal.h
new file mode 100644
index 0000000000..bffefbb9c1
--- /dev/null
+++ b/src/libsystemd-terminal/idev-internal.h
@@ -0,0 +1,165 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#pragma once
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <systemd/sd-bus.h>
+#include <systemd/sd-event.h>
+#include "hashmap.h"
+#include "idev.h"
+#include "list.h"
+#include "util.h"
+
+typedef struct idev_link                idev_link;
+typedef struct idev_device_vtable       idev_device_vtable;
+typedef struct idev_element             idev_element;
+typedef struct idev_element_vtable      idev_element_vtable;
+
+/*
+ * Element Links
+ */
+
+struct idev_link {
+        /* element-to-device connection */
+        LIST_FIELDS(idev_link, links_by_element);
+        idev_element *element;
+
+        /* device-to-element connection */
+        LIST_FIELDS(idev_link, links_by_device);
+        idev_device *device;
+};
+
+/*
+ * Devices
+ */
+
+struct idev_device_vtable {
+        void (*free) (idev_device *d);
+        void (*attach) (idev_device *d, idev_link *l);
+        void (*detach) (idev_device *d, idev_link *l);
+        int (*feed) (idev_device *d, idev_data *data);
+};
+
+struct idev_device {
+        const idev_device_vtable *vtable;
+        idev_session *session;
+        char *name;
+
+        LIST_HEAD(idev_link, links);
+
+        bool public : 1;
+        bool enabled : 1;
+};
+
+#define IDEV_DEVICE_INIT(_vtable, _session) ((idev_device){ \
+                .vtable = (_vtable), \
+                .session = (_session), \
+        })
+
+idev_device *idev_find_device(idev_session *s, const char *name);
+
+int idev_device_add(idev_device *d, const char *name);
+idev_device *idev_device_free(idev_device *d);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(idev_device*, idev_device_free);
+
+int idev_device_feed(idev_device *d, idev_data *data);
+void idev_device_feedback(idev_device *d, idev_data *data);
+
+/*
+ * Elements
+ */
+
+struct idev_element_vtable {
+        void (*free) (idev_element *e);
+        void (*enable) (idev_element *e);
+        void (*disable) (idev_element *e);
+        void (*open) (idev_element *e);
+        void (*close) (idev_element *e);
+        void (*feedback) (idev_element *e, idev_data *data);
+};
+
+struct idev_element {
+        const idev_element_vtable *vtable;
+        idev_session *session;
+        unsigned long n_open;
+        char *name;
+
+        LIST_HEAD(idev_link, links);
+
+        bool enabled : 1;
+        bool readable : 1;
+        bool writable : 1;
+};
+
+#define IDEV_ELEMENT_INIT(_vtable, _session) ((idev_element){ \
+                .vtable = (_vtable), \
+                .session = (_session), \
+        })
+
+idev_element *idev_find_element(idev_session *s, const char *name);
+
+int idev_element_add(idev_element *e, const char *name);
+idev_element *idev_element_free(idev_element *e);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(idev_element*, idev_element_free);
+
+int idev_element_feed(idev_element *e, idev_data *data);
+void idev_element_feedback(idev_element *e, idev_data *data);
+
+/*
+ * Sessions
+ */
+
+struct idev_session {
+        idev_context *context;
+        char *name;
+        char *path;
+
+        Hashmap *element_map;
+        Hashmap *device_map;
+
+        idev_event_fn event_fn;
+        void *userdata;
+
+        bool custom : 1;
+        bool managed : 1;
+        bool enabled : 1;
+};
+
+idev_session *idev_find_session(idev_context *c, const char *name);
+int idev_session_raise_device_data(idev_session *s, idev_device *d, idev_data *data);
+
+/*
+ * Contexts
+ */
+
+struct idev_context {
+        unsigned long ref;
+        sd_event *event;
+        sd_bus *sysbus;
+
+        Hashmap *session_map;
+        Hashmap *data_map;
+};
diff --git a/src/libsystemd-terminal/idev.c b/src/libsystemd-terminal/idev.c
new file mode 100644
index 0000000000..5e3080797a
--- /dev/null
+++ b/src/libsystemd-terminal/idev.c
@@ -0,0 +1,587 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <systemd/sd-bus.h>
+#include <systemd/sd-event.h>
+#include <systemd/sd-login.h>
+#include "hashmap.h"
+#include "idev.h"
+#include "idev-internal.h"
+#include "login-shared.h"
+#include "macro.h"
+#include "set.h"
+#include "util.h"
+
+static void element_open(idev_element *e);
+static void element_close(idev_element *e);
+
+/*
+ * Devices
+ */
+
+idev_device *idev_find_device(idev_session *s, const char *name) {
+        assert_return(s, NULL);
+        assert_return(name, NULL);
+
+        return hashmap_get(s->device_map, name);
+}
+
+int idev_device_add(idev_device *d, const char *name) {
+        int r;
+
+        assert_return(d, -EINVAL);
+        assert_return(d->vtable, -EINVAL);
+        assert_return(d->session, -EINVAL);
+        assert_return(name, -EINVAL);
+
+        d->name = strdup(name);
+        if (!d->name)
+                return -ENOMEM;
+
+        r = hashmap_put(d->session->device_map, d->name, d);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+idev_device *idev_device_free(idev_device *d) {
+        idev_device tmp;
+
+        if (!d)
+                return NULL;
+
+        assert(!d->enabled);
+        assert(!d->public);
+        assert(!d->links);
+        assert(d->vtable);
+        assert(d->vtable->free);
+
+        if (d->name)
+                hashmap_remove_value(d->session->device_map, d->name, d);
+
+        tmp = *d;
+        d->vtable->free(d);
+
+        free(tmp.name);
+
+        return NULL;
+}
+
+int idev_device_feed(idev_device *d, idev_data *data) {
+        assert(d);
+        assert(data);
+        assert(data->type < IDEV_DATA_CNT);
+
+        if (d->vtable->feed)
+                return d->vtable->feed(d, data);
+        else
+                return 0;
+}
+
+void idev_device_feedback(idev_device *d, idev_data *data) {
+        idev_link *l;
+
+        assert(d);
+        assert(data);
+        assert(data->type < IDEV_DATA_CNT);
+
+        LIST_FOREACH(links_by_device, l, d->links)
+                idev_element_feedback(l->element, data);
+}
+
+static void device_attach(idev_device *d, idev_link *l) {
+        assert(d);
+        assert(l);
+
+        if (d->vtable->attach)
+                d->vtable->attach(d, l);
+
+        if (d->enabled)
+                element_open(l->element);
+}
+
+static void device_detach(idev_device *d, idev_link *l) {
+        assert(d);
+        assert(l);
+
+        if (d->enabled)
+                element_close(l->element);
+
+        if (d->vtable->detach)
+                d->vtable->detach(d, l);
+}
+
+void idev_device_enable(idev_device *d) {
+        idev_link *l;
+
+        assert(d);
+
+        if (!d->enabled) {
+                d->enabled = true;
+                LIST_FOREACH(links_by_device, l, d->links)
+                        element_open(l->element);
+        }
+}
+
+void idev_device_disable(idev_device *d) {
+        idev_link *l;
+
+        assert(d);
+
+        if (d->enabled) {
+                d->enabled = false;
+                LIST_FOREACH(links_by_device, l, d->links)
+                        element_close(l->element);
+        }
+}
+
+/*
+ * Elements
+ */
+
+idev_element *idev_find_element(idev_session *s, const char *name) {
+        assert_return(s, NULL);
+        assert_return(name, NULL);
+
+        return hashmap_get(s->element_map, name);
+}
+
+int idev_element_add(idev_element *e, const char *name) {
+        int r;
+
+        assert_return(e, -EINVAL);
+        assert_return(e->vtable, -EINVAL);
+        assert_return(e->session, -EINVAL);
+        assert_return(name, -EINVAL);
+
+        e->name = strdup(name);
+        if (!e->name)
+                return -ENOMEM;
+
+        r = hashmap_put(e->session->element_map, e->name, e);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+idev_element *idev_element_free(idev_element *e) {
+        idev_element tmp;
+
+        if (!e)
+                return NULL;
+
+        assert(!e->enabled);
+        assert(!e->links);
+        assert(e->n_open == 0);
+        assert(e->vtable);
+        assert(e->vtable->free);
+
+        if (e->name)
+                hashmap_remove_value(e->session->element_map, e->name, e);
+
+        tmp = *e;
+        e->vtable->free(e);
+
+        free(tmp.name);
+
+        return NULL;
+}
+
+int idev_element_feed(idev_element *e, idev_data *data) {
+        int r, error = 0;
+        idev_link *l;
+
+        assert(e);
+        assert(data);
+        assert(data->type < IDEV_DATA_CNT);
+
+        LIST_FOREACH(links_by_element, l, e->links) {
+                r = idev_device_feed(l->device, data);
+                if (r != 0)
+                        error = r;
+        }
+
+        return error;
+}
+
+void idev_element_feedback(idev_element *e, idev_data *data) {
+        assert(e);
+        assert(data);
+        assert(data->type < IDEV_DATA_CNT);
+
+        if (e->vtable->feedback)
+               e->vtable->feedback(e, data);
+}
+
+static void element_open(idev_element *e) {
+        assert(e);
+
+        if (e->n_open++ == 0 && e->vtable->open)
+                e->vtable->open(e);
+}
+
+static void element_close(idev_element *e) {
+        assert(e);
+        assert(e->n_open > 0);
+
+        if (--e->n_open == 0 && e->vtable->close)
+                e->vtable->close(e);
+}
+
+static void element_enable(idev_element *e) {
+        assert(e);
+
+        if (!e->enabled) {
+                e->enabled = true;
+                if (e->vtable->enable)
+                        e->vtable->enable(e);
+        }
+}
+
+static void element_disable(idev_element *e) {
+        assert(e);
+
+        if (e->enabled) {
+                e->enabled = false;
+                if (e->vtable->disable)
+                        e->vtable->disable(e);
+        }
+}
+
+/*
+ * Sessions
+ */
+
+static int session_raise(idev_session *s, idev_event *ev) {
+        return s->event_fn(s, s->userdata, ev);
+}
+
+static int session_raise_device_add(idev_session *s, idev_device *d) {
+        idev_event event = {
+                .type = IDEV_EVENT_DEVICE_ADD,
+                .device_add = {
+                        .device = d,
+                },
+        };
+
+        return session_raise(s, &event);
+}
+
+static int session_raise_device_remove(idev_session *s, idev_device *d) {
+        idev_event event = {
+                .type = IDEV_EVENT_DEVICE_REMOVE,
+                .device_remove = {
+                        .device = d,
+                },
+        };
+
+        return session_raise(s, &event);
+}
+
+int idev_session_raise_device_data(idev_session *s, idev_device *d, idev_data *data) {
+        idev_event event = {
+                .type = IDEV_EVENT_DEVICE_DATA,
+                .device_data = {
+                        .device = d,
+                        .data = *data,
+                },
+        };
+
+        return session_raise(s, &event);
+}
+
+static int session_add_device(idev_session *s, idev_device *d) {
+        int r;
+
+        assert(s);
+        assert(d);
+
+        log_debug("idev: %s: add device '%s'", s->name, d->name);
+
+        d->public = true;
+        r = session_raise_device_add(s, d);
+        if (r != 0) {
+                d->public = false;
+                goto error;
+        }
+
+        return 0;
+
+error:
+        if (r < 0)
+                log_debug("idev: %s: error while adding device '%s': %s",
+                          s->name, d->name, strerror(-r));
+        return r;
+}
+
+static int session_remove_device(idev_session *s, idev_device *d) {
+        int r, error = 0;
+
+        assert(s);
+        assert(d);
+
+        log_debug("idev: %s: remove device '%s'", s->name, d->name);
+
+        d->public = false;
+        r = session_raise_device_remove(s, d);
+        if (r != 0)
+                error = r;
+
+        idev_device_disable(d);
+
+        if (error < 0)
+                log_debug("idev: %s: error while removing device '%s': %s",
+                          s->name, d->name, strerror(-error));
+        idev_device_free(d);
+        return error;
+}
+
+static int session_add_element(idev_session *s, idev_element *e) {
+        assert(s);
+        assert(e);
+
+        log_debug("idev: %s: add element '%s'", s->name, e->name);
+
+        if (s->enabled)
+                element_enable(e);
+
+        return 0;
+}
+
+static int session_remove_element(idev_session *s, idev_element *e) {
+        int r, error = 0;
+        idev_device *d;
+        idev_link *l;
+
+        assert(s);
+        assert(e);
+
+        log_debug("idev: %s: remove element '%s'", s->name, e->name);
+
+        while ((l = e->links)) {
+                d = l->device;
+                LIST_REMOVE(links_by_device, d->links, l);
+                LIST_REMOVE(links_by_element, e->links, l);
+                device_detach(d, l);
+
+                if (!d->links) {
+                        r = session_remove_device(s, d);
+                        if (r != 0)
+                                error = r;
+                }
+
+                l->device = NULL;
+                l->element = NULL;
+                free(l);
+        }
+
+        element_disable(e);
+
+        if (error < 0)
+                log_debug("idev: %s: error while removing element '%s': %s",
+                          s->name, e->name, strerror(-r));
+        idev_element_free(e);
+        return error;
+}
+
+idev_session *idev_find_session(idev_context *c, const char *name) {
+        assert_return(c, NULL);
+        assert_return(name, NULL);
+
+        return hashmap_get(c->session_map, name);
+}
+
+int idev_session_new(idev_session **out,
+                     idev_context *c,
+                     unsigned int flags,
+                     const char *name,
+                     idev_event_fn event_fn,
+                     void *userdata) {
+        _cleanup_(idev_session_freep) idev_session *s = NULL;
+        int r;
+
+        assert_return(out, -EINVAL);
+        assert_return(c, -EINVAL);
+        assert_return(name, -EINVAL);
+        assert_return(event_fn, -EINVAL);
+        assert_return((flags & IDEV_SESSION_CUSTOM) == !session_id_valid(name), -EINVAL);
+        assert_return(!(flags & IDEV_SESSION_CUSTOM) || !(flags & IDEV_SESSION_MANAGED), -EINVAL);
+        assert_return(!(flags & IDEV_SESSION_MANAGED) || c->sysbus, -EINVAL);
+
+        s = new0(idev_session, 1);
+        if (!s)
+                return -ENOMEM;
+
+        s->context = idev_context_ref(c);
+        s->custom = flags & IDEV_SESSION_CUSTOM;
+        s->managed = flags & IDEV_SESSION_MANAGED;
+        s->event_fn = event_fn;
+        s->userdata = userdata;
+
+        s->name = strdup(name);
+        if (!s->name)
+                return -ENOMEM;
+
+        if (s->managed) {
+                r = sd_bus_path_encode("/org/freedesktop/login1/session", s->name, &s->path);
+                if (r < 0)
+                        return r;
+        }
+
+        s->element_map = hashmap_new(string_hash_func, string_compare_func);
+        if (!s->element_map)
+                return -ENOMEM;
+
+        s->device_map = hashmap_new(string_hash_func, string_compare_func);
+        if (!s->device_map)
+                return -ENOMEM;
+
+        r = hashmap_put(c->session_map, s->name, s);
+        if (r < 0)
+                return r;
+
+        *out = s;
+        s = NULL;
+        return 0;
+}
+
+idev_session *idev_session_free(idev_session *s) {
+        idev_element *e;
+
+        if (!s)
+                return NULL;
+
+        while ((e = hashmap_first(s->element_map)))
+                session_remove_element(s, e);
+
+        assert(hashmap_size(s->device_map) == 0);
+
+        if (s->name)
+                hashmap_remove_value(s->context->session_map, s->name, s);
+
+        s->context = idev_context_unref(s->context);
+        hashmap_free(s->device_map);
+        hashmap_free(s->element_map);
+        free(s->path);
+        free(s->name);
+        free(s);
+
+        return NULL;
+}
+
+bool idev_session_is_enabled(idev_session *s) {
+        return s && s->enabled;
+}
+
+void idev_session_enable(idev_session *s) {
+        idev_element *e;
+        Iterator i;
+
+        assert(s);
+
+        if (!s->enabled) {
+                s->enabled = true;
+                HASHMAP_FOREACH(e, s->element_map, i)
+                        element_enable(e);
+        }
+}
+
+void idev_session_disable(idev_session *s) {
+        idev_element *e;
+        Iterator i;
+
+        assert(s);
+
+        if (s->enabled) {
+                s->enabled = false;
+                HASHMAP_FOREACH(e, s->element_map, i)
+                        element_disable(e);
+        }
+}
+
+/*
+ * Contexts
+ */
+
+int idev_context_new(idev_context **out, sd_event *event, sd_bus *sysbus) {
+        _cleanup_(idev_context_unrefp) idev_context *c = NULL;
+
+        assert_return(out, -EINVAL);
+        assert_return(event, -EINVAL);
+
+        c = new0(idev_context, 1);
+        if (!c)
+                return -ENOMEM;
+
+        c->ref = 1;
+        c->event = sd_event_ref(event);
+
+        if (sysbus)
+                c->sysbus = sd_bus_ref(sysbus);
+
+        c->session_map = hashmap_new(string_hash_func, string_compare_func);
+        if (!c->session_map)
+                return -ENOMEM;
+
+        c->data_map = hashmap_new(string_hash_func, string_compare_func);
+        if (!c->data_map)
+                return -ENOMEM;
+
+        *out = c;
+        c = NULL;
+        return 0;
+}
+
+static void context_cleanup(idev_context *c) {
+        assert(hashmap_size(c->data_map) == 0);
+        assert(hashmap_size(c->session_map) == 0);
+
+        hashmap_free(c->data_map);
+        hashmap_free(c->session_map);
+        c->sysbus = sd_bus_unref(c->sysbus);
+        c->event = sd_event_unref(c->event);
+        free(c);
+}
+
+idev_context *idev_context_ref(idev_context *c) {
+        assert_return(c, NULL);
+        assert_return(c->ref > 0, NULL);
+
+        ++c->ref;
+        return c;
+}
+
+idev_context *idev_context_unref(idev_context *c) {
+        if (!c)
+                return NULL;
+
+        assert_return(c->ref > 0, NULL);
+
+        if (--c->ref == 0)
+                context_cleanup(c);
+
+        return NULL;
+}
diff --git a/src/libsystemd-terminal/idev.h b/src/libsystemd-terminal/idev.h
new file mode 100644
index 0000000000..6f618f37af
--- /dev/null
+++ b/src/libsystemd-terminal/idev.h
@@ -0,0 +1,133 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+/*
+ * IDev
+ */
+
+#pragma once
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <systemd/sd-bus.h>
+#include <systemd/sd-event.h>
+#include "util.h"
+
+typedef struct idev_data                idev_data;
+
+typedef struct idev_event               idev_event;
+typedef struct idev_device              idev_device;
+typedef struct idev_session             idev_session;
+typedef struct idev_context             idev_context;
+
+/*
+ * Types
+ */
+
+enum {
+        IDEV_ELEMENT_CNT
+};
+
+enum {
+        IDEV_DEVICE_CNT
+};
+
+/*
+ * Data Packets
+ */
+
+enum {
+        IDEV_DATA_RESYNC,
+        IDEV_DATA_CNT
+};
+
+struct idev_data {
+        unsigned int type;
+        bool resync : 1;
+};
+
+/*
+ * Events
+ */
+
+enum {
+        IDEV_EVENT_DEVICE_ADD,
+        IDEV_EVENT_DEVICE_REMOVE,
+        IDEV_EVENT_DEVICE_DATA,
+        IDEV_EVENT_CNT
+};
+
+struct idev_event {
+        unsigned int type;
+        union {
+                struct {
+                        idev_device *device;
+                } device_add, device_remove;
+
+                struct {
+                        idev_device *device;
+                        idev_data data;
+                } device_data;
+        };
+};
+
+typedef int (*idev_event_fn) (idev_session *s, void *userdata, idev_event *ev);
+
+/*
+ * Devices
+ */
+
+void idev_device_enable(idev_device *d);
+void idev_device_disable(idev_device *d);
+
+/*
+ * Sessions
+ */
+
+enum {
+        IDEV_SESSION_CUSTOM                     = (1 << 0),
+        IDEV_SESSION_MANAGED                    = (1 << 1),
+};
+
+int idev_session_new(idev_session **out,
+                     idev_context *c,
+                     unsigned int flags,
+                     const char *name,
+                     idev_event_fn event_fn,
+                     void *userdata);
+idev_session *idev_session_free(idev_session *s);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(idev_session*, idev_session_free);
+
+bool idev_session_is_enabled(idev_session *s);
+void idev_session_enable(idev_session *s);
+void idev_session_disable(idev_session *s);
+
+/*
+ * Contexts
+ */
+
+int idev_context_new(idev_context **out, sd_event *event, sd_bus *sysbus);
+idev_context *idev_context_ref(idev_context *c);
+idev_context *idev_context_unref(idev_context *c);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(idev_context*, idev_context_unref);