Adding upstream version 241.upstream/241upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1004 insertions, 0 deletions

diff --git a/src/libsystemd/sd-device/device-enumerator.c b/src/libsystemd/sd-device/device-enumerator.c
new file mode 100644
index 0000000..20529aa
--- /dev/null
+++ b/src/libsystemd/sd-device/device-enumerator.c
@@ -0,0 +1,1004 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "sd-device.h"
+
+#include "alloc-util.h"
+#include "device-enumerator-private.h"
+#include "device-util.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "set.h"
+#include "string-util.h"
+#include "strv.h"
+#include "util.h"
+
+#define DEVICE_ENUMERATE_MAX_DEPTH 256
+
+typedef enum DeviceEnumerationType {
+        DEVICE_ENUMERATION_TYPE_DEVICES,
+        DEVICE_ENUMERATION_TYPE_SUBSYSTEMS,
+        _DEVICE_ENUMERATION_TYPE_MAX,
+        _DEVICE_ENUMERATION_TYPE_INVALID = -1,
+} DeviceEnumerationType;
+
+struct sd_device_enumerator {
+        unsigned n_ref;
+
+        DeviceEnumerationType type;
+        sd_device **devices;
+        size_t n_devices, n_allocated, current_device_index;
+        bool scan_uptodate;
+
+        Set *match_subsystem;
+        Set *nomatch_subsystem;
+        Hashmap *match_sysattr;
+        Hashmap *nomatch_sysattr;
+        Hashmap *match_property;
+        Set *match_sysname;
+        Set *match_tag;
+        sd_device *match_parent;
+        bool match_allow_uninitialized;
+};
+
+_public_ int sd_device_enumerator_new(sd_device_enumerator **ret) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *enumerator = NULL;
+
+        assert(ret);
+
+        enumerator = new(sd_device_enumerator, 1);
+        if (!enumerator)
+                return -ENOMEM;
+
+        *enumerator = (sd_device_enumerator) {
+                .n_ref = 1,
+                .type = _DEVICE_ENUMERATION_TYPE_INVALID,
+        };
+
+        *ret = TAKE_PTR(enumerator);
+
+        return 0;
+}
+
+static sd_device_enumerator *device_enumerator_free(sd_device_enumerator *enumerator) {
+        size_t i;
+
+        assert(enumerator);
+
+        for (i = 0; i < enumerator->n_devices; i++)
+                sd_device_unref(enumerator->devices[i]);
+
+        free(enumerator->devices);
+        set_free_free(enumerator->match_subsystem);
+        set_free_free(enumerator->nomatch_subsystem);
+        hashmap_free_free_free(enumerator->match_sysattr);
+        hashmap_free_free_free(enumerator->nomatch_sysattr);
+        hashmap_free_free_free(enumerator->match_property);
+        set_free_free(enumerator->match_sysname);
+        set_free_free(enumerator->match_tag);
+        sd_device_unref(enumerator->match_parent);
+
+        return mfree(enumerator);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device_enumerator, sd_device_enumerator, device_enumerator_free);
+
+_public_ int sd_device_enumerator_add_match_subsystem(sd_device_enumerator *enumerator, const char *subsystem, int match) {
+        Set **set;
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(subsystem, -EINVAL);
+
+        if (match)
+                set = &enumerator->match_subsystem;
+        else
+                set = &enumerator->nomatch_subsystem;
+
+        r = set_ensure_allocated(set, NULL);
+        if (r < 0)
+                return r;
+
+        r = set_put_strdup(*set, subsystem);
+        if (r < 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+_public_ int sd_device_enumerator_add_match_sysattr(sd_device_enumerator *enumerator, const char *_sysattr, const char *_value, int match) {
+        _cleanup_free_ char *sysattr = NULL, *value = NULL;
+        Hashmap **hashmap;
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(_sysattr, -EINVAL);
+
+        if (match)
+                hashmap = &enumerator->match_sysattr;
+        else
+                hashmap = &enumerator->nomatch_sysattr;
+
+        r = hashmap_ensure_allocated(hashmap, NULL);
+        if (r < 0)
+                return r;
+
+        sysattr = strdup(_sysattr);
+        if (!sysattr)
+                return -ENOMEM;
+
+        if (_value) {
+                value = strdup(_value);
+                if (!value)
+                        return -ENOMEM;
+        }
+
+        r = hashmap_put(*hashmap, sysattr, value);
+        if (r < 0)
+                return r;
+
+        sysattr = NULL;
+        value = NULL;
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+_public_ int sd_device_enumerator_add_match_property(sd_device_enumerator *enumerator, const char *_property, const char *_value) {
+        _cleanup_free_ char *property = NULL, *value = NULL;
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(_property, -EINVAL);
+
+        r = hashmap_ensure_allocated(&enumerator->match_property, NULL);
+        if (r < 0)
+                return r;
+
+        property = strdup(_property);
+        if (!property)
+                return -ENOMEM;
+
+        if (_value) {
+                value = strdup(_value);
+                if (!value)
+                        return -ENOMEM;
+        }
+
+        r = hashmap_put(enumerator->match_property, property, value);
+        if (r < 0)
+                return r;
+
+        property = NULL;
+        value = NULL;
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+_public_ int sd_device_enumerator_add_match_sysname(sd_device_enumerator *enumerator, const char *sysname) {
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(sysname, -EINVAL);
+
+        r = set_ensure_allocated(&enumerator->match_sysname, NULL);
+        if (r < 0)
+                return r;
+
+        r = set_put_strdup(enumerator->match_sysname, sysname);
+        if (r < 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+_public_ int sd_device_enumerator_add_match_tag(sd_device_enumerator *enumerator, const char *tag) {
+        int r;
+
+        assert_return(enumerator, -EINVAL);
+        assert_return(tag, -EINVAL);
+
+        r = set_ensure_allocated(&enumerator->match_tag, NULL);
+        if (r < 0)
+                return r;
+
+        r = set_put_strdup(enumerator->match_tag, tag);
+        if (r < 0)
+                return r;
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+_public_ int sd_device_enumerator_add_match_parent(sd_device_enumerator *enumerator, sd_device *parent) {
+        assert_return(enumerator, -EINVAL);
+        assert_return(parent, -EINVAL);
+
+        sd_device_unref(enumerator->match_parent);
+        enumerator->match_parent = sd_device_ref(parent);
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+_public_ int sd_device_enumerator_allow_uninitialized(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, -EINVAL);
+
+        enumerator->match_allow_uninitialized = true;
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+int device_enumerator_add_match_is_initialized(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, -EINVAL);
+
+        enumerator->match_allow_uninitialized = false;
+
+        enumerator->scan_uptodate = false;
+
+        return 0;
+}
+
+static int device_compare(sd_device * const *_a, sd_device * const *_b) {
+        sd_device *a = *(sd_device **)_a, *b = *(sd_device **)_b;
+        const char *devpath_a, *devpath_b, *sound_a;
+        bool delay_a, delay_b;
+        int r;
+
+        assert_se(sd_device_get_devpath(a, &devpath_a) >= 0);
+        assert_se(sd_device_get_devpath(b, &devpath_b) >= 0);
+
+        sound_a = strstr(devpath_a, "/sound/card");
+        if (sound_a) {
+                /* For sound cards the control device must be enumerated last to
+                 * make sure it's the final device node that gets ACLs applied.
+                 * Applications rely on this fact and use ACL changes on the
+                 * control node as an indicator that the ACL change of the
+                 * entire sound card completed. The kernel makes this guarantee
+                 * when creating those devices, and hence we should too when
+                 * enumerating them. */
+                sound_a += STRLEN("/sound/card");
+                sound_a = strchr(sound_a, '/');
+
+                if (sound_a) {
+                        unsigned prefix_len;
+
+                        prefix_len = sound_a - devpath_a;
+
+                        if (strncmp(devpath_a, devpath_b, prefix_len) == 0) {
+                                const char *sound_b;
+
+                                sound_b = devpath_b + prefix_len;
+
+                                if (startswith(sound_a, "/controlC") &&
+                                    !startswith(sound_b, "/contolC"))
+                                        return 1;
+
+                                if (!startswith(sound_a, "/controlC") &&
+                                    startswith(sound_b, "/controlC"))
+                                        return -1;
+                        }
+                }
+        }
+
+        /* md and dm devices are enumerated after all other devices */
+        delay_a = strstr(devpath_a, "/block/md") || strstr(devpath_a, "/block/dm-");
+        delay_b = strstr(devpath_b, "/block/md") || strstr(devpath_b, "/block/dm-");
+        r = CMP(delay_a, delay_b);
+        if (r != 0)
+                return r;
+
+        return strcmp(devpath_a, devpath_b);
+}
+
+int device_enumerator_add_device(sd_device_enumerator *enumerator, sd_device *device) {
+        assert_return(enumerator, -EINVAL);
+        assert_return(device, -EINVAL);
+
+        if (!GREEDY_REALLOC(enumerator->devices, enumerator->n_allocated, enumerator->n_devices + 1))
+                return -ENOMEM;
+
+        enumerator->devices[enumerator->n_devices++] = sd_device_ref(device);
+
+        return 0;
+}
+
+static bool match_sysattr_value(sd_device *device, const char *sysattr, const char *match_value) {
+        const char *value;
+        int r;
+
+        assert(device);
+        assert(sysattr);
+
+        r = sd_device_get_sysattr_value(device, sysattr, &value);
+        if (r < 0)
+                return false;
+
+        if (!match_value)
+                return true;
+
+        if (fnmatch(match_value, value, 0) == 0)
+                return true;
+
+        return false;
+}
+
+static bool match_sysattr(sd_device_enumerator *enumerator, sd_device *device) {
+        const char *sysattr;
+        const char *value;
+        Iterator i;
+
+        assert(enumerator);
+        assert(device);
+
+        HASHMAP_FOREACH_KEY(value, sysattr, enumerator->nomatch_sysattr, i)
+                if (match_sysattr_value(device, sysattr, value))
+                        return false;
+
+        HASHMAP_FOREACH_KEY(value, sysattr, enumerator->match_sysattr, i)
+                if (!match_sysattr_value(device, sysattr, value))
+                        return false;
+
+        return true;
+}
+
+static bool match_property(sd_device_enumerator *enumerator, sd_device *device) {
+        const char *property;
+        const char *value;
+        Iterator i;
+
+        assert(enumerator);
+        assert(device);
+
+        if (hashmap_isempty(enumerator->match_property))
+                return true;
+
+        HASHMAP_FOREACH_KEY(value, property, enumerator->match_property, i) {
+                const char *property_dev, *value_dev;
+
+                FOREACH_DEVICE_PROPERTY(device, property_dev, value_dev) {
+                        if (fnmatch(property, property_dev, 0) != 0)
+                                continue;
+
+                        if (!value && !value_dev)
+                                return true;
+
+                        if (!value || !value_dev)
+                                continue;
+
+                        if (fnmatch(value, value_dev, 0) == 0)
+                                return true;
+                }
+        }
+
+        return false;
+}
+
+static bool match_tag(sd_device_enumerator *enumerator, sd_device *device) {
+        const char *tag;
+        Iterator i;
+
+        assert(enumerator);
+        assert(device);
+
+        SET_FOREACH(tag, enumerator->match_tag, i)
+                if (!sd_device_has_tag(device, tag))
+                        return false;
+
+        return true;
+}
+
+static bool match_parent(sd_device_enumerator *enumerator, sd_device *device) {
+        const char *devpath, *devpath_dev;
+        int r;
+
+        assert(enumerator);
+        assert(device);
+
+        if (!enumerator->match_parent)
+                return true;
+
+        r = sd_device_get_devpath(enumerator->match_parent, &devpath);
+        assert(r >= 0);
+
+        r = sd_device_get_devpath(device, &devpath_dev);
+        assert(r >= 0);
+
+        return startswith(devpath_dev, devpath);
+}
+
+static bool match_sysname(sd_device_enumerator *enumerator, const char *sysname) {
+        const char *sysname_match;
+        Iterator i;
+
+        assert(enumerator);
+        assert(sysname);
+
+        if (set_isempty(enumerator->match_sysname))
+                return true;
+
+        SET_FOREACH(sysname_match, enumerator->match_sysname, i)
+                if (fnmatch(sysname_match, sysname, 0) == 0)
+                        return true;
+
+        return false;
+}
+
+static int enumerator_scan_dir_and_add_devices(sd_device_enumerator *enumerator, const char *basedir, const char *subdir1, const char *subdir2) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        char *path;
+        struct dirent *dent;
+        int r = 0;
+
+        assert(enumerator);
+        assert(basedir);
+
+        path = strjoina("/sys/", basedir, "/");
+
+        if (subdir1)
+                path = strjoina(path, subdir1, "/");
+
+        if (subdir2)
+                path = strjoina(path, subdir2, "/");
+
+        dir = opendir(path);
+        if (!dir)
+                return -errno;
+
+        FOREACH_DIRENT_ALL(dent, dir, return -errno) {
+                _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+                char syspath[strlen(path) + 1 + strlen(dent->d_name) + 1];
+                int initialized, k;
+
+                if (dent->d_name[0] == '.')
+                        continue;
+
+                if (!match_sysname(enumerator, dent->d_name))
+                        continue;
+
+                (void) sprintf(syspath, "%s%s", path, dent->d_name);
+
+                k = sd_device_new_from_syspath(&device, syspath);
+                if (k < 0) {
+                        if (k != -ENODEV)
+                                /* this is necessarily racey, so ignore missing devices */
+                                r = k;
+
+                        continue;
+                }
+
+                initialized = sd_device_get_is_initialized(device);
+                if (initialized < 0) {
+                        r = initialized;
+                        continue;
+                }
+
+                /*
+                 * All devices with a device node or network interfaces
+                 * possibly need udev to adjust the device node permission
+                 * or context, or rename the interface before it can be
+                 * reliably used from other processes.
+                 *
+                 * For now, we can only check these types of devices, we
+                 * might not store a database, and have no way to find out
+                 * for all other types of devices.
+                 */
+                if (!enumerator->match_allow_uninitialized &&
+                    !initialized &&
+                    (sd_device_get_devnum(device, NULL) >= 0 ||
+                     sd_device_get_ifindex(device, NULL) >= 0))
+                        continue;
+
+                if (!match_parent(enumerator, device))
+                        continue;
+
+                if (!match_tag(enumerator, device))
+                        continue;
+
+                if (!match_property(enumerator, device))
+                        continue;
+
+                if (!match_sysattr(enumerator, device))
+                        continue;
+
+                k = device_enumerator_add_device(enumerator, device);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static bool match_subsystem(sd_device_enumerator *enumerator, const char *subsystem) {
+        const char *subsystem_match;
+        Iterator i;
+
+        assert(enumerator);
+
+        if (!subsystem)
+                return false;
+
+        SET_FOREACH(subsystem_match, enumerator->nomatch_subsystem, i)
+                if (fnmatch(subsystem_match, subsystem, 0) == 0)
+                        return false;
+
+        if (set_isempty(enumerator->match_subsystem))
+                return true;
+
+        SET_FOREACH(subsystem_match, enumerator->match_subsystem, i)
+                if (fnmatch(subsystem_match, subsystem, 0) == 0)
+                        return true;
+
+        return false;
+}
+
+static int enumerator_scan_dir(sd_device_enumerator *enumerator, const char *basedir, const char *subdir, const char *subsystem) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        char *path;
+        struct dirent *dent;
+        int r = 0;
+
+        path = strjoina("/sys/", basedir);
+
+        dir = opendir(path);
+        if (!dir)
+                return -errno;
+
+        log_debug("sd-device-enumerator: Scanning %s", path);
+
+        FOREACH_DIRENT_ALL(dent, dir, return -errno) {
+                int k;
+
+                if (dent->d_name[0] == '.')
+                        continue;
+
+                if (!match_subsystem(enumerator, subsystem ? : dent->d_name))
+                        continue;
+
+                k = enumerator_scan_dir_and_add_devices(enumerator, basedir, dent->d_name, subdir);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int enumerator_scan_devices_tag(sd_device_enumerator *enumerator, const char *tag) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        char *path;
+        struct dirent *dent;
+        int r = 0;
+
+        assert(enumerator);
+        assert(tag);
+
+        path = strjoina("/run/udev/tags/", tag);
+
+        dir = opendir(path);
+        if (!dir) {
+                if (errno != ENOENT)
+                        return log_debug_errno(errno, "sd-device-enumerator: Failed to open tags directory %s: %m", path);
+                return 0;
+        }
+
+        /* TODO: filter away subsystems? */
+
+        FOREACH_DIRENT_ALL(dent, dir, return -errno) {
+                _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+                const char *subsystem, *sysname;
+                int k;
+
+                if (dent->d_name[0] == '.')
+                        continue;
+
+                k = sd_device_new_from_device_id(&device, dent->d_name);
+                if (k < 0) {
+                        if (k != -ENODEV)
+                                /* this is necessarily racy, so ignore missing devices */
+                                r = k;
+
+                        continue;
+                }
+
+                k = sd_device_get_subsystem(device, &subsystem);
+                if (k < 0) {
+                        r = k;
+                        continue;
+                }
+
+                if (!match_subsystem(enumerator, subsystem))
+                        continue;
+
+                k = sd_device_get_sysname(device, &sysname);
+                if (k < 0) {
+                        r = k;
+                        continue;
+                }
+
+                if (!match_sysname(enumerator, sysname))
+                        continue;
+
+                if (!match_parent(enumerator, device))
+                        continue;
+
+                if (!match_property(enumerator, device))
+                        continue;
+
+                if (!match_sysattr(enumerator, device))
+                        continue;
+
+                k = device_enumerator_add_device(enumerator, device);
+                if (k < 0) {
+                        r = k;
+                        continue;
+                }
+        }
+
+        return r;
+}
+
+static int enumerator_scan_devices_tags(sd_device_enumerator *enumerator) {
+        const char *tag;
+        Iterator i;
+        int r = 0;
+
+        assert(enumerator);
+
+        SET_FOREACH(tag, enumerator->match_tag, i) {
+                int k;
+
+                k = enumerator_scan_devices_tag(enumerator, tag);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+static int parent_add_child(sd_device_enumerator *enumerator, const char *path) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        const char *subsystem, *sysname;
+        int r;
+
+        r = sd_device_new_from_syspath(&device, path);
+        if (r == -ENODEV)
+                /* this is necessarily racy, so ignore missing devices */
+                return 0;
+        else if (r < 0)
+                return r;
+
+        r = sd_device_get_subsystem(device, &subsystem);
+        if (r == -ENOENT)
+                return 0;
+        if (r < 0)
+                return r;
+
+        if (!match_subsystem(enumerator, subsystem))
+                return 0;
+
+        r = sd_device_get_sysname(device, &sysname);
+        if (r < 0)
+                return r;
+
+        if (!match_sysname(enumerator, sysname))
+                return 0;
+
+        if (!match_property(enumerator, device))
+                return 0;
+
+        if (!match_sysattr(enumerator, device))
+                return 0;
+
+        r = device_enumerator_add_device(enumerator, device);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int parent_crawl_children(sd_device_enumerator *enumerator, const char *path, unsigned maxdepth) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        struct dirent *dent;
+        int r = 0;
+
+        dir = opendir(path);
+        if (!dir)
+                return log_debug_errno(errno, "sd-device-enumerator: Failed to open parent directory %s: %m", path);
+
+        FOREACH_DIRENT_ALL(dent, dir, return -errno) {
+                _cleanup_free_ char *child = NULL;
+                int k;
+
+                if (dent->d_name[0] == '.')
+                        continue;
+
+                if (dent->d_type != DT_DIR)
+                        continue;
+
+                child = strjoin(path, "/", dent->d_name);
+                if (!child)
+                        return -ENOMEM;
+
+                k = parent_add_child(enumerator, child);
+                if (k < 0)
+                        r = k;
+
+                if (maxdepth > 0)
+                        parent_crawl_children(enumerator, child, maxdepth - 1);
+                else
+                        log_debug("sd-device-enumerator: Max depth reached, %s: ignoring devices", child);
+        }
+
+        return r;
+}
+
+static int enumerator_scan_devices_children(sd_device_enumerator *enumerator) {
+        const char *path;
+        int r = 0, k;
+
+        r = sd_device_get_syspath(enumerator->match_parent, &path);
+        if (r < 0)
+                return r;
+
+        k = parent_add_child(enumerator, path);
+        if (k < 0)
+                r = k;
+
+        k = parent_crawl_children(enumerator, path, DEVICE_ENUMERATE_MAX_DEPTH);
+        if (k < 0)
+                r = k;
+
+        return r;
+}
+
+static int enumerator_scan_devices_all(sd_device_enumerator *enumerator) {
+        int r = 0;
+
+        log_debug("sd-device-enumerator: Scan all dirs");
+
+        if (access("/sys/subsystem", F_OK) >= 0) {
+                /* we have /subsystem/, forget all the old stuff */
+                r = enumerator_scan_dir(enumerator, "subsystem", "devices", NULL);
+                if (r < 0)
+                        return log_debug_errno(r, "sd-device-enumerator: Failed to scan /sys/subsystem: %m");
+        } else {
+                int k;
+
+                k = enumerator_scan_dir(enumerator, "bus", "devices", NULL);
+                if (k < 0) {
+                        log_debug_errno(k, "sd-device-enumerator: Failed to scan /sys/bus: %m");
+                        r = k;
+                }
+
+                k = enumerator_scan_dir(enumerator, "class", NULL, NULL);
+                if (k < 0) {
+                        log_debug_errno(k, "sd-device-enumerator: Failed to scan /sys/class: %m");
+                        r = k;
+                }
+        }
+
+        return r;
+}
+
+static void device_enumerator_dedup_devices(sd_device_enumerator *enumerator) {
+        sd_device **a, **b, **end;
+
+        assert(enumerator);
+
+        if (enumerator->n_devices <= 1)
+                return;
+
+        a = enumerator->devices + 1;
+        b = enumerator->devices;
+        end = enumerator->devices + enumerator->n_devices;
+
+        for (; a < end; a++) {
+                const char *devpath_a, *devpath_b;
+
+                assert_se(sd_device_get_devpath(*a, &devpath_a) >= 0);
+                assert_se(sd_device_get_devpath(*b, &devpath_b) >= 0);
+
+                if (path_equal(devpath_a, devpath_b))
+                        sd_device_unref(*a);
+                else
+                        *(++b) = *a;
+        }
+
+        enumerator->n_devices = b - enumerator->devices + 1;
+}
+
+int device_enumerator_scan_devices(sd_device_enumerator *enumerator) {
+        int r = 0, k;
+        size_t i;
+
+        assert(enumerator);
+
+        if (enumerator->scan_uptodate &&
+            enumerator->type == DEVICE_ENUMERATION_TYPE_DEVICES)
+                return 0;
+
+        for (i = 0; i < enumerator->n_devices; i++)
+                sd_device_unref(enumerator->devices[i]);
+
+        enumerator->n_devices = 0;
+
+        if (!set_isempty(enumerator->match_tag)) {
+                k = enumerator_scan_devices_tags(enumerator);
+                if (k < 0)
+                        r = k;
+        } else if (enumerator->match_parent) {
+                k = enumerator_scan_devices_children(enumerator);
+                if (k < 0)
+                        r = k;
+        } else {
+                k = enumerator_scan_devices_all(enumerator);
+                if (k < 0)
+                        r = k;
+        }
+
+        typesafe_qsort(enumerator->devices, enumerator->n_devices, device_compare);
+        device_enumerator_dedup_devices(enumerator);
+
+        enumerator->scan_uptodate = true;
+        enumerator->type = DEVICE_ENUMERATION_TYPE_DEVICES;
+
+        return r;
+}
+
+_public_ sd_device *sd_device_enumerator_get_device_first(sd_device_enumerator *enumerator) {
+        int r;
+
+        assert_return(enumerator, NULL);
+
+        r = device_enumerator_scan_devices(enumerator);
+        if (r < 0)
+                return NULL;
+
+        enumerator->current_device_index = 0;
+
+        if (enumerator->n_devices == 0)
+                return NULL;
+
+        return enumerator->devices[0];
+}
+
+_public_ sd_device *sd_device_enumerator_get_device_next(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate ||
+            enumerator->type != DEVICE_ENUMERATION_TYPE_DEVICES ||
+            enumerator->current_device_index + 1 >= enumerator->n_devices)
+                return NULL;
+
+        return enumerator->devices[++enumerator->current_device_index];
+}
+
+int device_enumerator_scan_subsystems(sd_device_enumerator *enumerator) {
+        const char *subsysdir;
+        int r = 0, k;
+        size_t i;
+
+        assert(enumerator);
+
+        if (enumerator->scan_uptodate &&
+            enumerator->type == DEVICE_ENUMERATION_TYPE_SUBSYSTEMS)
+                return 0;
+
+        for (i = 0; i < enumerator->n_devices; i++)
+                sd_device_unref(enumerator->devices[i]);
+
+        enumerator->n_devices = 0;
+
+        /* modules */
+        if (match_subsystem(enumerator, "module")) {
+                k = enumerator_scan_dir_and_add_devices(enumerator, "module", NULL, NULL);
+                if (k < 0) {
+                        log_debug_errno(k, "sd-device-enumerator: Failed to scan modules: %m");
+                        r = k;
+                }
+        }
+
+        if (access("/sys/subsystem", F_OK) >= 0)
+                subsysdir = "subsystem";
+        else
+                subsysdir = "bus";
+
+        /* subsystems (only buses support coldplug) */
+        if (match_subsystem(enumerator, "subsystem")) {
+                k = enumerator_scan_dir_and_add_devices(enumerator, subsysdir, NULL, NULL);
+                if (k < 0) {
+                        log_debug_errno(k, "sd-device-enumerator: Failed to scan subsystems: %m");
+                        r = k;
+                }
+        }
+
+        /* subsystem drivers */
+        if (match_subsystem(enumerator, "drivers")) {
+                k = enumerator_scan_dir(enumerator, subsysdir, "drivers", "drivers");
+                if (k < 0) {
+                        log_debug_errno(k, "sd-device-enumerator: Failed to scan drivers: %m");
+                        r = k;
+                }
+        }
+
+        typesafe_qsort(enumerator->devices, enumerator->n_devices, device_compare);
+        device_enumerator_dedup_devices(enumerator);
+
+        enumerator->scan_uptodate = true;
+        enumerator->type = DEVICE_ENUMERATION_TYPE_SUBSYSTEMS;
+
+        return r;
+}
+
+_public_ sd_device *sd_device_enumerator_get_subsystem_first(sd_device_enumerator *enumerator) {
+        int r;
+
+        assert_return(enumerator, NULL);
+
+        r = device_enumerator_scan_subsystems(enumerator);
+        if (r < 0)
+                return NULL;
+
+        enumerator->current_device_index = 0;
+
+        if (enumerator->n_devices == 0)
+                return NULL;
+
+        return enumerator->devices[0];
+}
+
+_public_ sd_device *sd_device_enumerator_get_subsystem_next(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate ||
+            enumerator->type != DEVICE_ENUMERATION_TYPE_SUBSYSTEMS ||
+            enumerator->current_device_index + 1 >= enumerator->n_devices)
+                return NULL;
+
+        return enumerator->devices[++enumerator->current_device_index];
+}
+
+sd_device *device_enumerator_get_first(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate)
+                return NULL;
+
+        enumerator->current_device_index = 0;
+
+        if (enumerator->n_devices == 0)
+                return NULL;
+
+        return enumerator->devices[0];
+}
+
+sd_device *device_enumerator_get_next(sd_device_enumerator *enumerator) {
+        assert_return(enumerator, NULL);
+
+        if (!enumerator->scan_uptodate ||
+            enumerator->current_device_index + 1 >= enumerator->n_devices)
+                return NULL;
+
+        return enumerator->devices[++enumerator->current_device_index];
+}
+
+sd_device **device_enumerator_get_devices(sd_device_enumerator *enumerator, size_t *ret_n_devices) {
+        assert(enumerator);
+        assert(ret_n_devices);
+
+        if (!enumerator->scan_uptodate)
+                return NULL;
+
+        *ret_n_devices = enumerator->n_devices;
+        return enumerator->devices;
+}