X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=src%2Fcore%2Fdevice.c;h=2d983cc565f382cf37cb760583744feb60d18fc4;hp=e83e797787905aa19a2cd5322af53ffead491730;hb=5bd4b173605142c7be493aa4d958ebaef21f421d;hpb=44a6b1b68029833893f6e9cee35aa27a974038f6

diff --git a/src/core/device.c b/src/core/device.c
index e83e79778..2d983cc56 100644
--- a/src/core/device.c
+++ b/src/core/device.c
@@ -23,21 +23,24 @@
 #include <sys/epoll.h>
 #include <libudev.h>
 
-#include "unit.h"
-#include "device.h"
-#include "strv.h"
 #include "log.h"
 #include "unit-name.h"
 #include "dbus-device.h"
-#include "def.h"
 #include "path-util.h"
+#include "udev-util.h"
+#include "unit.h"
+#include "swap.h"
+#include "device.h"
 
 static const UnitActiveState state_translation_table[_DEVICE_STATE_MAX] = {
         [DEVICE_DEAD] = UNIT_INACTIVE,
         [DEVICE_PLUGGED] = UNIT_ACTIVE
 };
 
+static int device_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata);
+
 static void device_unset_sysfs(Device *d) {
+        Hashmap *devices;
         Device *first;
 
         assert(d);
@@ -47,13 +50,14 @@ static void device_unset_sysfs(Device *d) {
 
         /* Remove this unit from the chain of devices which share the
          * same sysfs path. */
-        first = hashmap_get(UNIT(d)->manager->devices_by_sysfs, d->sysfs);
-        LIST_REMOVE(Device, same_sysfs, first, d);
+        devices = UNIT(d)->manager->devices_by_sysfs;
+        first = hashmap_get(devices, d->sysfs);
+        LIST_REMOVE(same_sysfs, first, d);
 
         if (first)
-                hashmap_remove_and_replace(UNIT(d)->manager->devices_by_sysfs, d->sysfs, first->sysfs, first);
+                hashmap_remove_and_replace(devices, d->sysfs, first->sysfs, first);
         else
-                hashmap_remove(UNIT(d)->manager->devices_by_sysfs, d->sysfs);
+                hashmap_remove(devices, d->sysfs);
 
         free(d->sysfs);
         d->sysfs = NULL;
@@ -70,10 +74,10 @@ static void device_init(Unit *u) {
          * indefinitely for plugged in devices, something which cannot
          * happen for the other units since their operations time out
          * anyway. */
-        UNIT(d)->job_timeout = DEFAULT_TIMEOUT_USEC;
+        u->job_timeout = u->manager->default_timeout_start_usec;
 
-        UNIT(d)->ignore_on_isolate = true;
-        UNIT(d)->ignore_on_snapshot = true;
+        u->ignore_on_isolate = true;
+        u->ignore_on_snapshot = true;
 }
 
 static void device_done(Unit *u) {
@@ -92,7 +96,7 @@ static void device_set_state(Device *d, DeviceState state) {
         d->state = state;
 
         if (state != old_state)
-                log_debug_unit(UNIT(d)->id,
+                log_unit_debug(UNIT(d)->id,
                                "%s changed %s -> %s", UNIT(d)->id,
                                device_state_to_string(old_state),
                                device_state_to_string(state));
@@ -137,7 +141,7 @@ _pure_ static const char *device_sub_state_to_string(Unit *u) {
 }
 
 static int device_add_escaped_name(Unit *u, const char *dn) {
-        char *e;
+        _cleanup_free_ char *e = NULL;
         int r;
 
         assert(u);
@@ -149,8 +153,6 @@ static int device_add_escaped_name(Unit *u, const char *dn) {
                 return -ENOMEM;
 
         r = unit_add_name(u, e);
-        free(e);
-
         if (r < 0 && r != -EEXIST)
                 return r;
 
@@ -158,7 +160,7 @@ static int device_add_escaped_name(Unit *u, const char *dn) {
 }
 
 static int device_find_escape_name(Manager *m, const char *dn, Unit **_u) {
-        char *e;
+        _cleanup_free_ char *e = NULL;
         Unit *u;
 
         assert(m);
@@ -171,8 +173,6 @@ static int device_find_escape_name(Manager *m, const char *dn, Unit **_u) {
                 return -ENOMEM;
 
         u = manager_get_unit(m, e);
-        free(e);
-
         if (u) {
                 *_u = u;
                 return 1;
@@ -181,18 +181,94 @@ static int device_find_escape_name(Manager *m, const char *dn, Unit **_u) {
         return 0;
 }
 
+static int device_make_description(Unit *u, struct udev_device *dev, const char *path) {
+        const char *model;
+
+        assert(u);
+        assert(dev);
+        assert(path);
+
+        model = udev_device_get_property_value(dev, "ID_MODEL_FROM_DATABASE");
+        if (!model)
+                model = udev_device_get_property_value(dev, "ID_MODEL");
+
+        if (model) {
+                const char *label;
+
+                /* Try to concatenate the device model string with a label, if there is one */
+                label = udev_device_get_property_value(dev, "ID_FS_LABEL");
+                if (!label)
+                        label = udev_device_get_property_value(dev, "ID_PART_ENTRY_NAME");
+                if (!label)
+                        label = udev_device_get_property_value(dev, "ID_PART_ENTRY_NUMBER");
+
+                if (label) {
+                        _cleanup_free_ char *j;
+
+                        j = strjoin(model, " ", label, NULL);
+                        if (j)
+                                return unit_set_description(u, j);
+                }
+
+                return unit_set_description(u, model);
+        }
+
+        return unit_set_description(u, path);
+}
+
+static int device_add_udev_wants(Unit *u, struct udev_device *dev) {
+        const char *wants;
+        const char *word, *state;
+        size_t l;
+        int r;
+        const char *property;
+
+        assert(u);
+        assert(dev);
+
+        property = u->manager->running_as == SYSTEMD_USER ? "SYSTEMD_USER_WANTS" : "SYSTEMD_WANTS";
+        wants = udev_device_get_property_value(dev, property);
+        if (!wants)
+                return 0;
+
+        FOREACH_WORD_QUOTED(word, l, wants, state) {
+                _cleanup_free_ char *n = NULL;
+                char e[l+1];
+
+                memcpy(e, word, l);
+                e[l] = 0;
+
+                n = unit_name_mangle(e, MANGLE_NOGLOB);
+                if (!n)
+                        return -ENOMEM;
+
+                r = unit_add_dependency_by_name(u, UNIT_WANTS, n, NULL, true);
+                if (r < 0)
+                        return r;
+        }
+        if (!isempty(state))
+                log_unit_warning(u->id, "Property %s on %s has trailing garbage, ignoring.",
+                                 property, strna(udev_device_get_syspath(dev)));
+
+        return 0;
+}
+
 static int device_update_unit(Manager *m, struct udev_device *dev, const char *path, bool main) {
-        const char *sysfs, *model;
+        const char *sysfs;
         Unit *u = NULL;
-        int r;
         bool delete;
+        int r;
 
         assert(m);
+        assert(dev);
+        assert(path);
 
-        if (!(sysfs = udev_device_get_syspath(dev)))
-                return -ENOMEM;
+        sysfs = udev_device_get_syspath(dev);
+        if (!sysfs)
+                return 0;
 
-        if ((r = device_find_escape_name(m, path, &u)) < 0)
+        r = device_find_escape_name(m, path, &u);
+        if (r < 0)
                 return r;
 
         if (u && DEVICE(u)->sysfs && !path_equal(DEVICE(u)->sysfs, sysfs))
@@ -203,7 +279,7 @@ static int device_update_unit(Manager *m, struct udev_device *dev, const char *p
 
                 u = unit_new(m, sizeof(Device));
                 if (!u)
-                        return -ENOMEM;
+                        return log_oom();
 
                 r = device_add_escaped_name(u, path);
                 if (r < 0)
@@ -220,88 +296,43 @@ static int device_update_unit(Manager *m, struct udev_device *dev, const char *p
         if (!DEVICE(u)->sysfs) {
                 Device *first;
 
-                if (!(DEVICE(u)->sysfs = strdup(sysfs))) {
+                DEVICE(u)->sysfs = strdup(sysfs);
+                if (!DEVICE(u)->sysfs) {
                         r = -ENOMEM;
                         goto fail;
                 }
 
-                if (!m->devices_by_sysfs)
-                        if (!(m->devices_by_sysfs = hashmap_new(string_hash_func, string_compare_func))) {
-                                r = -ENOMEM;
-                                goto fail;
-                        }
+                r = hashmap_ensure_allocated(&m->devices_by_sysfs, &string_hash_ops);
+                if (r < 0)
+                        goto fail;
 
                 first = hashmap_get(m->devices_by_sysfs, sysfs);
-                LIST_PREPEND(Device, same_sysfs, first, DEVICE(u));
+                LIST_PREPEND(same_sysfs, first, DEVICE(u));
 
-                if ((r = hashmap_replace(m->devices_by_sysfs, DEVICE(u)->sysfs, first)) < 0)
+                r = hashmap_replace(m->devices_by_sysfs, DEVICE(u)->sysfs, first);
+                if (r < 0)
                         goto fail;
         }
 
-        if ((model = udev_device_get_property_value(dev, "ID_MODEL_FROM_DATABASE")) ||
-            (model = udev_device_get_property_value(dev, "ID_MODEL"))) {
-                if ((r = unit_set_description(u, model)) < 0)
-                        goto fail;
-        } else
-                if ((r = unit_set_description(u, path)) < 0)
-                        goto fail;
+        device_make_description(u, dev, path);
 
         if (main) {
                 /* The additional systemd udev properties we only
                  * interpret for the main object */
-                const char *wants, *alias;
-
-                alias = udev_device_get_property_value(dev, "SYSTEMD_ALIAS");
-                if (alias) {
-                        char *state, *w;
-                        size_t l;
-
-                        FOREACH_WORD_QUOTED(w, l, alias, state) {
-                                char *e;
-
-                                e = strndup(w, l);
-                                if (!e) {
-                                        r = -ENOMEM;
-                                        goto fail;
-                                }
-
-                                if (!is_path(e)) {
-                                        log_warning("SYSTEMD_ALIAS for %s is not a path, ignoring: %s", sysfs, e);
-                                        free(e);
-                                } else {
-                                        device_update_unit(m, dev, e, false);
-                                        free(e);
-                                }
-                        }
-                }
 
-                wants = udev_device_get_property_value(dev, "SYSTEMD_WANTS");
-                if (wants) {
-                        char *state, *w;
-                        size_t l;
-
-                        FOREACH_WORD_QUOTED(w, l, wants, state) {
-                                char *e;
-
-                                e = strndup(w, l);
-                                if (!e) {
-                                        r = -ENOMEM;
-                                        goto fail;
-                                }
-
-                                r = unit_add_dependency_by_name(u, UNIT_WANTS, e, NULL, true);
-                                free(e);
-                                if (r < 0)
-                                        goto fail;
-                        }
-                }
+                r = device_add_udev_wants(u, dev);
+                if (r < 0)
+                        goto fail;
         }
 
+        /* Note that this won't dispatch the load queue, the caller
+         * has to do that if needed and appropriate */
+
         unit_add_to_dbus_queue(u);
         return 0;
 
 fail:
-        log_warning("Failed to load device unit: %s", strerror(-r));
+        log_warning_errno(r, "Failed to load device unit: %m");
 
         if (delete && u)
                 unit_free(u);
@@ -309,15 +340,16 @@ fail:
         return r;
 }
 
-static int device_process_new_device(Manager *m, struct udev_device *dev, bool update_state) {
-        const char *sysfs, *dn;
+static int device_process_new_device(Manager *m, struct udev_device *dev) {
+        const char *sysfs, *dn, *alias;
         struct udev_list_entry *item = NULL, *first = NULL;
         int r;
 
         assert(m);
 
-        if (!(sysfs = udev_device_get_syspath(dev)))
-                return -ENOMEM;
+        sysfs = udev_device_get_syspath(dev);
+        if (!sysfs)
+                return 0;
 
         /* Add the main unit named after the sysfs path */
         r = device_update_unit(m, dev, sysfs, true);
@@ -325,7 +357,8 @@ static int device_process_new_device(Manager *m, struct udev_device *dev, bool u
                 return r;
 
         /* Add an additional unit for the device node */
-        if ((dn = udev_device_get_devnode(dev)))
+        dn = udev_device_get_devnode(dev);
+        if (dn)
                 device_update_unit(m, dev, dn, false);
 
         /* Add additional units for all symlinks */
@@ -347,7 +380,7 @@ static int device_process_new_device(Manager *m, struct udev_device *dev, bool u
                  * same /dev/disk/by-label/xxx link because they have
                  * the same label. We want to make sure that the same
                  * device that won the symlink wins in systemd, so we
-                 * check the device node major/minor*/
+                 * check the device node major/minor */
                 if (stat(p, &st) >= 0)
                         if ((!S_ISBLK(st.st_mode) && !S_ISCHR(st.st_mode)) ||
                             st.st_rdev != udev_device_get_devnum(dev))
@@ -356,34 +389,45 @@ static int device_process_new_device(Manager *m, struct udev_device *dev, bool u
                 device_update_unit(m, dev, p, false);
         }
 
-        if (update_state) {
-                Device *d, *l;
+        /* Add additional units for all explicitly configured
+         * aliases */
+        alias = udev_device_get_property_value(dev, "SYSTEMD_ALIAS");
+        if (alias) {
+                const char *word, *state;
+                size_t l;
 
-                manager_dispatch_load_queue(m);
+                FOREACH_WORD_QUOTED(word, l, alias, state) {
+                        char e[l+1];
 
-                l = hashmap_get(m->devices_by_sysfs, sysfs);
-                LIST_FOREACH(same_sysfs, d, l)
-                        device_set_state(d, DEVICE_PLUGGED);
+                        memcpy(e, word, l);
+                        e[l] = 0;
+
+                        if (path_is_absolute(e))
+                                device_update_unit(m, dev, e, false);
+                        else
+                                log_warning("SYSTEMD_ALIAS for %s is not an absolute path, ignoring: %s", sysfs, e);
+                }
+                if (!isempty(state))
+                        log_warning("SYSTEMD_ALIAS for %s has trailing garbage, ignoring.", sysfs);
         }
 
         return 0;
 }
 
-static int device_process_path(Manager *m, const char *path, bool update_state) {
-        int r;
-        struct udev_device *dev;
+static void device_set_path_plugged(Manager *m, struct udev_device *dev) {
+        const char *sysfs;
+        Device *d, *l;
 
         assert(m);
-        assert(path);
+        assert(dev);
 
-        if (!(dev = udev_device_new_from_syspath(m->udev, path))) {
-                log_warning("Failed to get udev device object from udev for path %s.", path);
-                return -ENOMEM;
-        }
+        sysfs = udev_device_get_syspath(dev);
+        if (!sysfs)
+                return;
 
-        r = device_process_new_device(m, dev, update_state);
-        udev_device_unref(dev);
-        return r;
+        l = hashmap_get(m->devices_by_sysfs, sysfs);
+        LIST_FOREACH(same_sysfs, d, l)
+                device_set_state(d, DEVICE_PLUGGED);
 }
 
 static int device_process_removed_device(Manager *m, struct udev_device *dev) {
@@ -393,7 +437,8 @@ static int device_process_removed_device(Manager *m, struct udev_device *dev) {
         assert(m);
         assert(dev);
 
-        if (!(sysfs = udev_device_get_syspath(dev)))
+        sysfs = udev_device_get_syspath(dev);
+        if (!sysfs)
                 return -ENOMEM;
 
         /* Remove all units of this sysfs path */
@@ -405,6 +450,34 @@ static int device_process_removed_device(Manager *m, struct udev_device *dev) {
         return 0;
 }
 
+static bool device_is_ready(struct udev_device *dev) {
+        const char *ready;
+
+        assert(dev);
+
+        ready = udev_device_get_property_value(dev, "SYSTEMD_READY");
+        if (!ready)
+                return true;
+
+        return parse_boolean(ready) != 0;
+}
+
+static int device_process_new_path(Manager *m, const char *path) {
+        _cleanup_udev_device_unref_ struct udev_device *dev = NULL;
+
+        assert(m);
+        assert(path);
+
+        dev = udev_device_new_from_syspath(m->udev, path);
+        if (!dev)
+                return log_oom();
+
+        if (!device_is_ready(dev))
+                return 0;
+
+        return device_process_new_device(m, dev);
+}
+
 static Unit *device_following(Unit *u) {
         Device *d = DEVICE(u);
         Device *other, *first = NULL;
@@ -429,70 +502,67 @@ static Unit *device_following(Unit *u) {
         return UNIT(first);
 }
 
-static int device_following_set(Unit *u, Set **_s) {
-        Device *d = DEVICE(u);
-        Device *other;
-        Set *s;
+static int device_following_set(Unit *u, Set **_set) {
+        Device *d = DEVICE(u), *other;
+        Set *set;
         int r;
 
         assert(d);
-        assert(_s);
+        assert(_set);
 
-        if (!d->same_sysfs_prev && !d->same_sysfs_next) {
-                *_s = NULL;
+        if (LIST_JUST_US(same_sysfs, d)) {
+                *_set = NULL;
                 return 0;
         }
 
-        if (!(s = set_new(NULL, NULL)))
+        set = set_new(NULL);
+        if (!set)
                 return -ENOMEM;
 
-        for (other = d->same_sysfs_next; other; other = other->same_sysfs_next)
-                if ((r = set_put(s, other)) < 0)
+        LIST_FOREACH_AFTER(same_sysfs, other, d) {
+                r = set_put(set, other);
+                if (r < 0)
                         goto fail;
+        }
 
-        for (other = d->same_sysfs_prev; other; other = other->same_sysfs_prev)
-                if ((r = set_put(s, other)) < 0)
+        LIST_FOREACH_BEFORE(same_sysfs, other, d) {
+                r = set_put(set, other);
+                if (r < 0)
                         goto fail;
+        }
 
-        *_s = s;
+        *_set = set;
         return 1;
 
 fail:
-        set_free(s);
+        set_free(set);
         return r;
 }
 
 static void device_shutdown(Manager *m) {
         assert(m);
 
+        m->udev_event_source = sd_event_source_unref(m->udev_event_source);
+
         if (m->udev_monitor) {
                 udev_monitor_unref(m->udev_monitor);
                 m->udev_monitor = NULL;
         }
 
-        if (m->udev) {
-                udev_unref(m->udev);
-                m->udev = NULL;
-        }
-
         hashmap_free(m->devices_by_sysfs);
         m->devices_by_sysfs = NULL;
 }
 
 static int device_enumerate(Manager *m) {
-        int r;
-        struct udev_enumerate *e = NULL;
+        _cleanup_udev_enumerate_unref_ struct udev_enumerate *e = NULL;
         struct udev_list_entry *item = NULL, *first = NULL;
+        int r;
 
         assert(m);
 
-        if (!m->udev) {
-                struct epoll_event ev;
-
-                if (!(m->udev = udev_new()))
-                        return -ENOMEM;
-
-                if (!(m->udev_monitor = udev_monitor_new_from_netlink(m->udev, "udev"))) {
+        if (!m->udev_monitor) {
+                m->udev_monitor = udev_monitor_new_from_netlink(m->udev, "udev");
+                if (!m->udev_monitor) {
                         r = -ENOMEM;
                         goto fail;
                 }
@@ -502,101 +572,116 @@ static int device_enumerate(Manager *m) {
                  * during boot. */
                 udev_monitor_set_receive_buffer_size(m->udev_monitor, 128*1024*1024);
 
-                if (udev_monitor_filter_add_match_tag(m->udev_monitor, "systemd") < 0) {
-                        r = -ENOMEM;
+                r = udev_monitor_filter_add_match_tag(m->udev_monitor, "systemd");
+                if (r < 0)
                         goto fail;
-                }
 
-                if (udev_monitor_enable_receiving(m->udev_monitor) < 0) {
-                        r = -EIO;
+                r = udev_monitor_enable_receiving(m->udev_monitor);
+                if (r < 0)
                         goto fail;
-                }
-
-                m->udev_watch.type = WATCH_UDEV;
-                m->udev_watch.fd = udev_monitor_get_fd(m->udev_monitor);
-
-                zero(ev);
-                ev.events = EPOLLIN;
-                ev.data.ptr = &m->udev_watch;
 
-                if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->udev_watch.fd, &ev) < 0)
-                        return -errno;
+                r = sd_event_add_io(m->event, &m->udev_event_source, udev_monitor_get_fd(m->udev_monitor), EPOLLIN, device_dispatch_io, m);
+                if (r < 0)
+                        goto fail;
         }
 
-        if (!(e = udev_enumerate_new(m->udev))) {
+        e = udev_enumerate_new(m->udev);
+        if (!e) {
                 r = -ENOMEM;
                 goto fail;
         }
-        if (udev_enumerate_add_match_tag(e, "systemd") < 0) {
-                r = -EIO;
+
+        r = udev_enumerate_add_match_tag(e, "systemd");
+        if (r < 0)
                 goto fail;
-        }
 
-        if (udev_enumerate_scan_devices(e) < 0) {
-                r = -EIO;
+        r = udev_enumerate_add_match_is_initialized(e);
+        if (r < 0)
+                goto fail;
+
+        r = udev_enumerate_scan_devices(e);
+        if (r < 0)
                 goto fail;
-        }
 
         first = udev_enumerate_get_list_entry(e);
         udev_list_entry_foreach(item, first)
-                device_process_path(m, udev_list_entry_get_name(item), false);
+                device_process_new_path(m, udev_list_entry_get_name(item));
 
-        udev_enumerate_unref(e);
         return 0;
 
 fail:
-        if (e)
-                udev_enumerate_unref(e);
-
         device_shutdown(m);
         return r;
 }
 
-void device_fd_event(Manager *m, int events) {
-        struct udev_device *dev;
+static int device_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
+        _cleanup_udev_device_unref_ struct udev_device *dev = NULL;
+        Manager *m = userdata;
+        const char *action;
         int r;
-        const char *action, *ready;
 
         assert(m);
 
-        if (events != EPOLLIN) {
+        if (revents != EPOLLIN) {
                 static RATELIMIT_DEFINE(limit, 10*USEC_PER_SEC, 5);
 
                 if (!ratelimit_test(&limit))
-                        log_error("Failed to get udev event: %m");
-                if (!(events & EPOLLIN))
-                        return;
+                        log_error_errno(errno, "Failed to get udev event: %m");
+                if (!(revents & EPOLLIN))
+                        return 0;
         }
 
-        if (!(dev = udev_monitor_receive_device(m->udev_monitor))) {
-                /*
-                 * libudev might filter-out devices which pass the bloom filter,
-                 * so getting NULL here is not necessarily an error
-                 */
-                return;
-        }
+        /*
+         * libudev might filter-out devices which pass the bloom
+         * filter, so getting NULL here is not necessarily an error.
+         */
+        dev = udev_monitor_receive_device(m->udev_monitor);
+        if (!dev)
+                return 0;
 
-        if (!(action = udev_device_get_action(dev))) {
+        action = udev_device_get_action(dev);
+        if (!action) {
                 log_error("Failed to get udev action string.");
-                goto fail;
+                return 0;
         }
 
-        ready = udev_device_get_property_value(dev, "SYSTEMD_READY");
+        if (streq(action, "remove") || !device_is_ready(dev))  {
+                r = device_process_removed_device(m, dev);
+                if (r < 0)
+                        log_error_errno(r, "Failed to process device remove event: %m");
+
+                r = swap_process_removed_device(m, dev);
+                if (r < 0)
+                        log_error_errno(r, "Failed to process swap device remove event: %m");
 
-        if (streq(action, "remove") || (ready && parse_boolean(ready) == 0)) {
-                if ((r = device_process_removed_device(m, dev)) < 0) {
-                        log_error("Failed to process udev device event: %s", strerror(-r));
-                        goto fail;
-                }
         } else {
-                if ((r = device_process_new_device(m, dev, true)) < 0) {
-                        log_error("Failed to process udev device event: %s", strerror(-r));
-                        goto fail;
-                }
+                r = device_process_new_device(m, dev);
+                if (r < 0)
+                        log_error_errno(r, "Failed to process device new event: %m");
+
+                r = swap_process_new_device(m, dev);
+                if (r < 0)
+                        log_error_errno(r, "Failed to process swap device new event: %m");
+
+                manager_dispatch_load_queue(m);
+
+                device_set_path_plugged(m, dev);
         }
 
-fail:
-        udev_device_unref(dev);
+        return 0;
+}
+
+static bool device_supported(Manager *m) {
+        static int read_only = -1;
+        assert(m);
+
+        /* If /sys is read-only we don't support device units, and any
+         * attempts to start one should fail immediately. */
+
+        if (read_only < 0)
+                read_only = path_is_read_only_fs("/sys");
+
+        return read_only <= 0;
 }
 
 static const char* const device_state_table[_DEVICE_STATE_MAX] = {
@@ -616,9 +701,9 @@ const UnitVTable device_vtable = {
         .no_instances = true,
 
         .init = device_init,
-
-        .load = unit_load_fragment_and_dropin_optional,
         .done = device_done,
+        .load = unit_load_fragment_and_dropin_optional,
+
         .coldplug = device_coldplug,
 
         .dump = device_dump,
@@ -627,14 +712,14 @@ const UnitVTable device_vtable = {
         .sub_state_to_string = device_sub_state_to_string,
 
         .bus_interface = "org.freedesktop.systemd1.Device",
-        .bus_message_handler = bus_device_message_handler,
-        .bus_invalidating_properties =  bus_device_invalidating_properties,
+        .bus_vtable = bus_device_vtable,
 
         .following = device_following,
         .following_set = device_following_set,
 
         .enumerate = device_enumerate,
         .shutdown = device_shutdown,
+        .supported = device_supported,
 
         .status_message_formats = {
                 .starting_stopping = {