Adding upstream version 241.upstream/241upstream

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

1 files changed, 1864 insertions, 0 deletions

diff --git a/src/libsystemd/sd-device/sd-device.c b/src/libsystemd/sd-device/sd-device.c
new file mode 100644
index 0000000..2a69f2e
--- /dev/null
+++ b/src/libsystemd/sd-device/sd-device.c
@@ -0,0 +1,1864 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <ctype.h>
+#include <net/if.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+
+#include "sd-device.h"
+
+#include "alloc-util.h"
+#include "device-internal.h"
+#include "device-private.h"
+#include "device-util.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "hashmap.h"
+#include "macro.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "set.h"
+#include "socket-util.h"
+#include "stat-util.h"
+#include "stdio-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "strxcpyx.h"
+#include "util.h"
+
+int device_new_aux(sd_device **ret) {
+        sd_device *device;
+
+        assert(ret);
+
+        device = new(sd_device, 1);
+        if (!device)
+                return -ENOMEM;
+
+        *device = (sd_device) {
+                .n_ref = 1,
+                .watch_handle = -1,
+                .devmode = (mode_t) -1,
+                .devuid = (uid_t) -1,
+                .devgid = (gid_t) -1,
+        };
+
+        *ret = device;
+        return 0;
+}
+
+static sd_device *device_free(sd_device *device) {
+        assert(device);
+
+        sd_device_unref(device->parent);
+        free(device->syspath);
+        free(device->sysname);
+        free(device->devtype);
+        free(device->devname);
+        free(device->subsystem);
+        free(device->driver_subsystem);
+        free(device->driver);
+        free(device->id_filename);
+        free(device->properties_strv);
+        free(device->properties_nulstr);
+
+        ordered_hashmap_free_free_free(device->properties);
+        ordered_hashmap_free_free_free(device->properties_db);
+        hashmap_free_free_free(device->sysattr_values);
+        set_free_free(device->sysattrs);
+        set_free_free(device->tags);
+        set_free_free(device->devlinks);
+
+        return mfree(device);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device, sd_device, device_free);
+
+int device_add_property_aux(sd_device *device, const char *_key, const char *_value, bool db) {
+        OrderedHashmap **properties;
+
+        assert(device);
+        assert(_key);
+
+        if (db)
+                properties = &device->properties_db;
+        else
+                properties = &device->properties;
+
+        if (_value) {
+                _cleanup_free_ char *key = NULL, *value = NULL, *old_key = NULL, *old_value = NULL;
+                int r;
+
+                r = ordered_hashmap_ensure_allocated(properties, &string_hash_ops);
+                if (r < 0)
+                        return r;
+
+                key = strdup(_key);
+                if (!key)
+                        return -ENOMEM;
+
+                value = strdup(_value);
+                if (!value)
+                        return -ENOMEM;
+
+                old_value = ordered_hashmap_get2(*properties, key, (void**) &old_key);
+
+                r = ordered_hashmap_replace(*properties, key, value);
+                if (r < 0)
+                        return r;
+
+                key = NULL;
+                value = NULL;
+        } else {
+                _cleanup_free_ char *key = NULL;
+                _cleanup_free_ char *value = NULL;
+
+                value = ordered_hashmap_remove2(*properties, _key, (void**) &key);
+        }
+
+        if (!db) {
+                device->properties_generation++;
+                device->properties_buf_outdated = true;
+        }
+
+        return 0;
+}
+
+int device_add_property_internal(sd_device *device, const char *key, const char *value) {
+        return device_add_property_aux(device, key, value, false);
+}
+
+int device_set_syspath(sd_device *device, const char *_syspath, bool verify) {
+        _cleanup_free_ char *syspath = NULL;
+        const char *devpath;
+        int r;
+
+        assert(device);
+        assert(_syspath);
+
+        /* must be a subdirectory of /sys */
+        if (!path_startswith(_syspath, "/sys/"))
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "sd-device: Syspath '%s' is not a subdirectory of /sys",
+                                       _syspath);
+
+        if (verify) {
+                r = chase_symlinks(_syspath, NULL, 0, &syspath);
+                if (r == -ENOENT)
+                        return -ENODEV; /* the device does not exist (any more?) */
+                if (r < 0)
+                        return log_debug_errno(r, "sd-device: Failed to get target of '%s': %m", _syspath);
+
+                if (!path_startswith(syspath, "/sys")) {
+                        _cleanup_free_ char *real_sys = NULL, *new_syspath = NULL;
+                        char *p;
+
+                        /* /sys is a symlink to somewhere sysfs is mounted on? In that case, we convert the path to real sysfs to "/sys". */
+                        r = chase_symlinks("/sys", NULL, 0, &real_sys);
+                        if (r < 0)
+                                return log_debug_errno(r, "sd-device: Failed to chase symlink /sys: %m");
+
+                        p = path_startswith(syspath, real_sys);
+                        if (!p)
+                                return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
+                                                       "sd-device: Canonicalized path '%s' does not starts with sysfs mount point '%s'",
+                                                       syspath, real_sys);
+
+                        new_syspath = strjoin("/sys/", p);
+                        if (!new_syspath)
+                                return -ENOMEM;
+
+                        free_and_replace(syspath, new_syspath);
+                        path_simplify(syspath, false);
+                }
+
+                if (path_startswith(syspath,  "/sys/devices/")) {
+                        char *path;
+
+                        /* all 'devices' require an 'uevent' file */
+                        path = strjoina(syspath, "/uevent");
+                        r = access(path, F_OK);
+                        if (r < 0) {
+                                if (errno == ENOENT)
+                                        /* this is not a valid device */
+                                        return -ENODEV;
+
+                                return log_debug_errno(errno, "sd-device: %s does not have an uevent file: %m", syspath);
+                        }
+                } else {
+                        /* everything else just needs to be a directory */
+                        if (!is_dir(syspath, false))
+                                return -ENODEV;
+                }
+        } else {
+                syspath = strdup(_syspath);
+                if (!syspath)
+                        return -ENOMEM;
+        }
+
+        devpath = syspath + STRLEN("/sys");
+
+        r = device_add_property_internal(device, "DEVPATH", devpath);
+        if (r < 0)
+                return r;
+
+        free_and_replace(device->syspath, syspath);
+        device->devpath = devpath;
+        return 0;
+}
+
+_public_ int sd_device_new_from_syspath(sd_device **ret, const char *syspath) {
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(syspath, -EINVAL);
+
+        r = device_new_aux(&device);
+        if (r < 0)
+                return r;
+
+        r = device_set_syspath(device, syspath, true);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(device);
+        return 0;
+}
+
+_public_ int sd_device_new_from_devnum(sd_device **ret, char type, dev_t devnum) {
+        char *syspath;
+        char id[DECIMAL_STR_MAX(unsigned) * 2 + 1];
+
+        assert_return(ret, -EINVAL);
+        assert_return(IN_SET(type, 'b', 'c'), -EINVAL);
+
+        /* use /sys/dev/{block,char}/<maj>:<min> link */
+        snprintf(id, sizeof(id), "%u:%u", major(devnum), minor(devnum));
+
+        syspath = strjoina("/sys/dev/", (type == 'b' ? "block" : "char"), "/", id);
+
+        return sd_device_new_from_syspath(ret, syspath);
+}
+
+_public_ int sd_device_new_from_subsystem_sysname(sd_device **ret, const char *subsystem, const char *sysname) {
+        char *name, *syspath;
+        size_t len = 0;
+
+        assert_return(ret, -EINVAL);
+        assert_return(subsystem, -EINVAL);
+        assert_return(sysname, -EINVAL);
+
+        if (streq(subsystem, "subsystem")) {
+                syspath = strjoina("/sys/subsystem/", sysname);
+                if (access(syspath, F_OK) >= 0)
+                        return sd_device_new_from_syspath(ret, syspath);
+
+                syspath = strjoina("/sys/bus/", sysname);
+                if (access(syspath, F_OK) >= 0)
+                        return sd_device_new_from_syspath(ret, syspath);
+
+                syspath = strjoina("/sys/class/", sysname);
+                if (access(syspath, F_OK) >= 0)
+                        return sd_device_new_from_syspath(ret, syspath);
+        } else  if (streq(subsystem, "module")) {
+                syspath = strjoina("/sys/module/", sysname);
+                if (access(syspath, F_OK) >= 0)
+                        return sd_device_new_from_syspath(ret, syspath);
+        } else if (streq(subsystem, "drivers")) {
+                char subsys[PATH_MAX];
+                char *driver;
+
+                strscpy(subsys, sizeof(subsys), sysname);
+                driver = strchr(subsys, ':');
+                if (driver) {
+                        driver[0] = '\0';
+                        driver++;
+
+                        syspath = strjoina("/sys/subsystem/", subsys, "/drivers/", driver);
+                        if (access(syspath, F_OK) >= 0)
+                                return sd_device_new_from_syspath(ret, syspath);
+
+                        syspath = strjoina("/sys/bus/", subsys, "/drivers/", driver);
+                        if (access(syspath, F_OK) >= 0)
+                                return sd_device_new_from_syspath(ret, syspath);
+                }
+        }
+
+        /* translate sysname back to sysfs filename */
+        name = strdupa(sysname);
+        while (name[len] != '\0') {
+                if (name[len] == '/')
+                        name[len] = '!';
+
+                len++;
+        }
+
+        syspath = strjoina("/sys/subsystem/", subsystem, "/devices/", name);
+        if (access(syspath, F_OK) >= 0)
+                return sd_device_new_from_syspath(ret, syspath);
+
+        syspath = strjoina("/sys/bus/", subsystem, "/devices/", name);
+        if (access(syspath, F_OK) >= 0)
+                return sd_device_new_from_syspath(ret, syspath);
+
+        syspath = strjoina("/sys/class/", subsystem, "/", name);
+        if (access(syspath, F_OK) >= 0)
+                return sd_device_new_from_syspath(ret, syspath);
+
+        syspath = strjoina("/sys/firmware/", subsystem, "/", sysname);
+        if (access(syspath, F_OK) >= 0)
+                return sd_device_new_from_syspath(ret, syspath);
+
+        return -ENODEV;
+}
+
+int device_set_devtype(sd_device *device, const char *_devtype) {
+        _cleanup_free_ char *devtype = NULL;
+        int r;
+
+        assert(device);
+        assert(_devtype);
+
+        devtype = strdup(_devtype);
+        if (!devtype)
+                return -ENOMEM;
+
+        r = device_add_property_internal(device, "DEVTYPE", devtype);
+        if (r < 0)
+                return r;
+
+        free_and_replace(device->devtype, devtype);
+
+        return 0;
+}
+
+int device_set_ifindex(sd_device *device, const char *_ifindex) {
+        int ifindex, r;
+
+        assert(device);
+        assert(_ifindex);
+
+        r = parse_ifindex(_ifindex, &ifindex);
+        if (r < 0)
+                return r;
+
+        r = device_add_property_internal(device, "IFINDEX", _ifindex);
+        if (r < 0)
+                return r;
+
+        device->ifindex = ifindex;
+
+        return 0;
+}
+
+int device_set_devname(sd_device *device, const char *_devname) {
+        _cleanup_free_ char *devname = NULL;
+        int r;
+
+        assert(device);
+        assert(_devname);
+
+        if (_devname[0] != '/') {
+                r = asprintf(&devname, "/dev/%s", _devname);
+                if (r < 0)
+                        return -ENOMEM;
+        } else {
+                devname = strdup(_devname);
+                if (!devname)
+                        return -ENOMEM;
+        }
+
+        r = device_add_property_internal(device, "DEVNAME", devname);
+        if (r < 0)
+                return r;
+
+        free_and_replace(device->devname, devname);
+
+        return 0;
+}
+
+int device_set_devmode(sd_device *device, const char *_devmode) {
+        unsigned devmode;
+        int r;
+
+        assert(device);
+        assert(_devmode);
+
+        r = safe_atou(_devmode, &devmode);
+        if (r < 0)
+                return r;
+
+        if (devmode > 07777)
+                return -EINVAL;
+
+        r = device_add_property_internal(device, "DEVMODE", _devmode);
+        if (r < 0)
+                return r;
+
+        device->devmode = devmode;
+
+        return 0;
+}
+
+int device_set_devnum(sd_device *device, const char *major, const char *minor) {
+        unsigned maj = 0, min = 0;
+        int r;
+
+        assert(device);
+        assert(major);
+
+        r = safe_atou(major, &maj);
+        if (r < 0)
+                return r;
+        if (!maj)
+                return 0;
+
+        if (minor) {
+                r = safe_atou(minor, &min);
+                if (r < 0)
+                        return r;
+        }
+
+        r = device_add_property_internal(device, "MAJOR", major);
+        if (r < 0)
+                return r;
+
+        if (minor) {
+                r = device_add_property_internal(device, "MINOR", minor);
+                if (r < 0)
+                        return r;
+        }
+
+        device->devnum = makedev(maj, min);
+
+        return 0;
+}
+
+static int handle_uevent_line(sd_device *device, const char *key, const char *value, const char **major, const char **minor) {
+        int r;
+
+        assert(device);
+        assert(key);
+        assert(value);
+        assert(major);
+        assert(minor);
+
+        if (streq(key, "DEVTYPE")) {
+                r = device_set_devtype(device, value);
+                if (r < 0)
+                        return r;
+        } else if (streq(key, "IFINDEX")) {
+                r = device_set_ifindex(device, value);
+                if (r < 0)
+                        return r;
+        } else if (streq(key, "DEVNAME")) {
+                r = device_set_devname(device, value);
+                if (r < 0)
+                        return r;
+        } else if (streq(key, "DEVMODE")) {
+                r = device_set_devmode(device, value);
+                if (r < 0)
+                        return r;
+        } else if (streq(key, "MAJOR"))
+                *major = value;
+        else if (streq(key, "MINOR"))
+                *minor = value;
+        else {
+                r = device_add_property_internal(device, key, value);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int device_read_uevent_file(sd_device *device) {
+        _cleanup_free_ char *uevent = NULL;
+        const char *syspath, *key = NULL, *value = NULL, *major = NULL, *minor = NULL;
+        char *path;
+        size_t uevent_len;
+        unsigned i;
+        int r;
+
+        enum {
+                PRE_KEY,
+                KEY,
+                PRE_VALUE,
+                VALUE,
+                INVALID_LINE,
+        } state = PRE_KEY;
+
+        assert(device);
+
+        if (device->uevent_loaded || device->sealed)
+                return 0;
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        path = strjoina(syspath, "/uevent");
+
+        r = read_full_file(path, &uevent, &uevent_len);
+        if (r == -EACCES) {
+                /* empty uevent files may be write-only */
+                device->uevent_loaded = true;
+                return 0;
+        }
+        if (r == -ENOENT)
+                /* some devices may not have uevent files, see set_syspath() */
+                return 0;
+        if (r < 0)
+                return log_device_debug_errno(device, r, "sd-device: Failed to read uevent file '%s': %m", path);
+
+        device->uevent_loaded = true;
+
+        for (i = 0; i < uevent_len; i++)
+                switch (state) {
+                case PRE_KEY:
+                        if (!strchr(NEWLINE, uevent[i])) {
+                                key = &uevent[i];
+
+                                state = KEY;
+                        }
+
+                        break;
+                case KEY:
+                        if (uevent[i] == '=') {
+                                uevent[i] = '\0';
+
+                                state = PRE_VALUE;
+                        } else if (strchr(NEWLINE, uevent[i])) {
+                                uevent[i] = '\0';
+                                log_device_debug(device, "sd-device: Invalid uevent line '%s', ignoring", key);
+
+                                state = PRE_KEY;
+                        }
+
+                        break;
+                case PRE_VALUE:
+                        value = &uevent[i];
+                        state = VALUE;
+
+                        _fallthrough_; /* to handle empty property */
+                case VALUE:
+                        if (strchr(NEWLINE, uevent[i])) {
+                                uevent[i] = '\0';
+
+                                r = handle_uevent_line(device, key, value, &major, &minor);
+                                if (r < 0)
+                                        log_device_debug_errno(device, r, "sd-device: Failed to handle uevent entry '%s=%s', ignoring: %m", key, value);
+
+                                state = PRE_KEY;
+                        }
+
+                        break;
+                default:
+                        assert_not_reached("Invalid state when parsing uevent file");
+                }
+
+        if (major) {
+                r = device_set_devnum(device, major, minor);
+                if (r < 0)
+                        log_device_debug_errno(device, r, "sd-device: Failed to set 'MAJOR=%s' or 'MINOR=%s' from '%s', ignoring: %m", major, minor, path);
+        }
+
+        return 0;
+}
+
+_public_ int sd_device_get_ifindex(sd_device *device, int *ifindex) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (device->ifindex <= 0)
+                return -ENOENT;
+
+        if (ifindex)
+                *ifindex = device->ifindex;
+
+        return 0;
+}
+
+_public_ int sd_device_new_from_device_id(sd_device **ret, const char *id) {
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(id, -EINVAL);
+
+        switch (id[0]) {
+        case 'b':
+        case 'c': {
+                dev_t devt;
+
+                if (isempty(id))
+                        return -EINVAL;
+
+                r = parse_dev(id + 1, &devt);
+                if (r < 0)
+                        return r;
+
+                return sd_device_new_from_devnum(ret, id[0], devt);
+        }
+
+        case 'n': {
+                _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+                _cleanup_close_ int sk = -1;
+                struct ifreq ifr = {};
+                int ifindex;
+
+                r = parse_ifindex(&id[1], &ifr.ifr_ifindex);
+                if (r < 0)
+                        return r;
+
+                sk = socket_ioctl_fd();
+                if (sk < 0)
+                        return sk;
+
+                r = ioctl(sk, SIOCGIFNAME, &ifr);
+                if (r < 0)
+                        return -errno;
+
+                r = sd_device_new_from_subsystem_sysname(&device, "net", ifr.ifr_name);
+                if (r < 0)
+                        return r;
+
+                r = sd_device_get_ifindex(device, &ifindex);
+                if (r < 0)
+                        return r;
+
+                /* this is racey, so we might end up with the wrong device */
+                if (ifr.ifr_ifindex != ifindex)
+                        return -ENODEV;
+
+                *ret = TAKE_PTR(device);
+                return 0;
+        }
+
+        case '+': {
+                char subsys[PATH_MAX];
+                char *sysname;
+
+                (void) strscpy(subsys, sizeof(subsys), id + 1);
+                sysname = strchr(subsys, ':');
+                if (!sysname)
+                        return -EINVAL;
+
+                sysname[0] = '\0';
+                sysname++;
+
+                return sd_device_new_from_subsystem_sysname(ret, subsys, sysname);
+        }
+
+        default:
+                return -EINVAL;
+        }
+}
+
+_public_ int sd_device_get_syspath(sd_device *device, const char **ret) {
+        assert_return(device, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        assert(path_startswith(device->syspath, "/sys/"));
+
+        *ret = device->syspath;
+
+        return 0;
+}
+
+static int device_new_from_child(sd_device **ret, sd_device *child) {
+        _cleanup_free_ char *path = NULL;
+        const char *subdir, *syspath;
+        int r;
+
+        assert(ret);
+        assert(child);
+
+        r = sd_device_get_syspath(child, &syspath);
+        if (r < 0)
+                return r;
+
+        path = strdup(syspath);
+        if (!path)
+                return -ENOMEM;
+        subdir = path + STRLEN("/sys");
+
+        for (;;) {
+                char *pos;
+
+                pos = strrchr(subdir, '/');
+                if (!pos || pos < subdir + 2)
+                        break;
+
+                *pos = '\0';
+
+                r = sd_device_new_from_syspath(ret, path);
+                if (r < 0)
+                        continue;
+
+                return 0;
+        }
+
+        return -ENODEV;
+}
+
+_public_ int sd_device_get_parent(sd_device *child, sd_device **ret) {
+
+        assert_return(ret, -EINVAL);
+        assert_return(child, -EINVAL);
+
+        if (!child->parent_set) {
+                child->parent_set = true;
+
+                (void) device_new_from_child(&child->parent, child);
+        }
+
+        if (!child->parent)
+                return -ENOENT;
+
+        *ret = child->parent;
+        return 0;
+}
+
+int device_set_subsystem(sd_device *device, const char *_subsystem) {
+        _cleanup_free_ char *subsystem = NULL;
+        int r;
+
+        assert(device);
+        assert(_subsystem);
+
+        subsystem = strdup(_subsystem);
+        if (!subsystem)
+                return -ENOMEM;
+
+        r = device_add_property_internal(device, "SUBSYSTEM", subsystem);
+        if (r < 0)
+                return r;
+
+        device->subsystem_set = true;
+        return free_and_replace(device->subsystem, subsystem);
+}
+
+static int device_set_drivers_subsystem(sd_device *device, const char *_subsystem) {
+        _cleanup_free_ char *subsystem = NULL;
+        int r;
+
+        assert(device);
+        assert(_subsystem);
+        assert(*_subsystem);
+
+        subsystem = strdup(_subsystem);
+        if (!subsystem)
+                return -ENOMEM;
+
+        r = device_set_subsystem(device, "drivers");
+        if (r < 0)
+                return r;
+
+        return free_and_replace(device->driver_subsystem, subsystem);
+}
+
+_public_ int sd_device_get_subsystem(sd_device *device, const char **ret) {
+        const char *syspath, *drivers = NULL;
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(device, -EINVAL);
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        if (!device->subsystem_set) {
+                _cleanup_free_ char *subsystem = NULL;
+                char *path;
+
+                /* read 'subsystem' link */
+                path = strjoina(syspath, "/subsystem");
+                r = readlink_value(path, &subsystem);
+                if (r >= 0)
+                        r = device_set_subsystem(device, subsystem);
+                /* use implicit names */
+                else if (path_startswith(device->devpath, "/module/"))
+                        r = device_set_subsystem(device, "module");
+                else if (!(drivers = strstr(syspath, "/drivers/")) &&
+                         PATH_STARTSWITH_SET(device->devpath, "/subsystem/",
+                                                              "/class/",
+                                                              "/bus/"))
+                        r = device_set_subsystem(device, "subsystem");
+                if (r < 0 && r != -ENOENT)
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set subsystem for %s: %m", device->devpath);
+
+                device->subsystem_set = true;
+        } else if (!device->driver_subsystem_set)
+                drivers = strstr(syspath, "/drivers/");
+
+        if (!device->driver_subsystem_set) {
+                if (drivers) {
+                        _cleanup_free_ char *subpath = NULL;
+
+                        subpath = strndup(syspath, drivers - syspath);
+                        if (!subpath)
+                                r = -ENOMEM;
+                        else {
+                                const char *subsys;
+
+                                subsys = strrchr(subpath, '/');
+                                if (!subsys)
+                                        r = -EINVAL;
+                                else
+                                        r = device_set_drivers_subsystem(device, subsys + 1);
+                        }
+                        if (r < 0 && r != -ENOENT)
+                                return log_device_debug_errno(device, r, "sd-device: Failed to set subsystem for driver %s: %m", device->devpath);
+                }
+
+                device->driver_subsystem_set = true;
+        }
+
+        if (!device->subsystem)
+                return -ENOENT;
+
+        *ret = device->subsystem;
+        return 0;
+}
+
+_public_ int sd_device_get_devtype(sd_device *device, const char **devtype) {
+        int r;
+
+        assert(devtype);
+        assert(device);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (!device->devtype)
+                return -ENOENT;
+
+        *devtype = device->devtype;
+
+        return 0;
+}
+
+_public_ int sd_device_get_parent_with_subsystem_devtype(sd_device *child, const char *subsystem, const char *devtype, sd_device **ret) {
+        sd_device *parent = NULL;
+        int r;
+
+        assert_return(child, -EINVAL);
+        assert_return(subsystem, -EINVAL);
+
+        r = sd_device_get_parent(child, &parent);
+        while (r >= 0) {
+                const char *parent_subsystem = NULL;
+                const char *parent_devtype = NULL;
+
+                (void) sd_device_get_subsystem(parent, &parent_subsystem);
+                if (streq_ptr(parent_subsystem, subsystem)) {
+                        if (!devtype)
+                                break;
+
+                        (void) sd_device_get_devtype(parent, &parent_devtype);
+                        if (streq_ptr(parent_devtype, devtype))
+                                break;
+                }
+                r = sd_device_get_parent(parent, &parent);
+        }
+
+        if (r < 0)
+                return r;
+
+        *ret = parent;
+        return 0;
+}
+
+_public_ int sd_device_get_devnum(sd_device *device, dev_t *devnum) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (major(device->devnum) <= 0)
+                return -ENOENT;
+
+        if (devnum)
+                *devnum = device->devnum;
+
+        return 0;
+}
+
+int device_set_driver(sd_device *device, const char *_driver) {
+        _cleanup_free_ char *driver = NULL;
+        int r;
+
+        assert(device);
+        assert(_driver);
+
+        driver = strdup(_driver);
+        if (!driver)
+                return -ENOMEM;
+
+        r = device_add_property_internal(device, "DRIVER", driver);
+        if (r < 0)
+                return r;
+
+        device->driver_set = true;
+        return free_and_replace(device->driver, driver);
+}
+
+_public_ int sd_device_get_driver(sd_device *device, const char **ret) {
+        assert_return(device, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!device->driver_set) {
+                _cleanup_free_ char *driver = NULL;
+                const char *syspath;
+                char *path;
+                int r;
+
+                r = sd_device_get_syspath(device, &syspath);
+                if (r < 0)
+                        return r;
+
+                path = strjoina(syspath, "/driver");
+                r = readlink_value(path, &driver);
+                if (r >= 0) {
+                        r = device_set_driver(device, driver);
+                        if (r < 0)
+                                return log_device_debug_errno(device, r, "sd-device: Failed to set driver for %s: %m", device->devpath);
+                } else if (r == -ENOENT)
+                        device->driver_set = true;
+                else
+                        return log_device_debug_errno(device, r, "sd-device: Failed to set driver for %s: %m", device->devpath);
+        }
+
+        if (!device->driver)
+                return -ENOENT;
+
+        *ret = device->driver;
+        return 0;
+}
+
+_public_ int sd_device_get_devpath(sd_device *device, const char **devpath) {
+        assert_return(device, -EINVAL);
+        assert_return(devpath, -EINVAL);
+
+        assert(device->devpath);
+        assert(device->devpath[0] == '/');
+
+        *devpath = device->devpath;
+        return 0;
+}
+
+_public_ int sd_device_get_devname(sd_device *device, const char **devname) {
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(devname, -EINVAL);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        if (!device->devname)
+                return -ENOENT;
+
+        assert(path_startswith(device->devname, "/dev/"));
+
+        *devname = device->devname;
+        return 0;
+}
+
+static int device_set_sysname(sd_device *device) {
+        _cleanup_free_ char *sysname = NULL;
+        const char *sysnum = NULL;
+        const char *pos;
+        size_t len = 0;
+
+        if (!device->devpath)
+                return -EINVAL;
+
+        pos = strrchr(device->devpath, '/');
+        if (!pos)
+                return -EINVAL;
+        pos++;
+
+        /* devpath is not a root directory */
+        if (*pos == '\0' || pos <= device->devpath)
+                return -EINVAL;
+
+        sysname = strdup(pos);
+        if (!sysname)
+                return -ENOMEM;
+
+        /* some devices have '!' in their name, change that to '/' */
+        while (sysname[len] != '\0') {
+                if (sysname[len] == '!')
+                        sysname[len] = '/';
+
+                len++;
+        }
+
+        /* trailing number */
+        while (len > 0 && isdigit(sysname[--len]))
+                sysnum = &sysname[len];
+
+        if (len == 0)
+                sysnum = NULL;
+
+        device->sysname_set = true;
+        device->sysnum = sysnum;
+        return free_and_replace(device->sysname, sysname);
+}
+
+_public_ int sd_device_get_sysname(sd_device *device, const char **ret) {
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!device->sysname_set) {
+                r = device_set_sysname(device);
+                if (r < 0)
+                        return r;
+        }
+
+        assert_return(device->sysname, -ENOENT);
+
+        *ret = device->sysname;
+        return 0;
+}
+
+_public_ int sd_device_get_sysnum(sd_device *device, const char **ret) {
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!device->sysname_set) {
+                r = device_set_sysname(device);
+                if (r < 0)
+                        return r;
+        }
+
+        if (!device->sysnum)
+                return -ENOENT;
+
+        *ret = device->sysnum;
+        return 0;
+}
+
+static bool is_valid_tag(const char *tag) {
+        assert(tag);
+
+        return !strchr(tag, ':') && !strchr(tag, ' ');
+}
+
+int device_add_tag(sd_device *device, const char *tag) {
+        int r;
+
+        assert(device);
+        assert(tag);
+
+        if (!is_valid_tag(tag))
+                return -EINVAL;
+
+        r = set_ensure_allocated(&device->tags, &string_hash_ops);
+        if (r < 0)
+                return r;
+
+        r = set_put_strdup(device->tags, tag);
+        if (r < 0)
+                return r;
+
+        device->tags_generation++;
+        device->property_tags_outdated = true;
+
+        return 0;
+}
+
+int device_add_devlink(sd_device *device, const char *devlink) {
+        int r;
+
+        assert(device);
+        assert(devlink);
+
+        r = set_ensure_allocated(&device->devlinks, &string_hash_ops);
+        if (r < 0)
+                return r;
+
+        r = set_put_strdup(device->devlinks, devlink);
+        if (r < 0)
+                return r;
+
+        device->devlinks_generation++;
+        device->property_devlinks_outdated = true;
+
+        return 0;
+}
+
+static int device_add_property_internal_from_string(sd_device *device, const char *str) {
+        _cleanup_free_ char *key = NULL;
+        char *value;
+
+        assert(device);
+        assert(str);
+
+        key = strdup(str);
+        if (!key)
+                return -ENOMEM;
+
+        value = strchr(key, '=');
+        if (!value)
+                return -EINVAL;
+
+        *value = '\0';
+
+        if (isempty(++value))
+                value = NULL;
+
+        return device_add_property_internal(device, key, value);
+}
+
+int device_set_usec_initialized(sd_device *device, usec_t when) {
+        char s[DECIMAL_STR_MAX(usec_t)];
+        int r;
+
+        assert(device);
+
+        xsprintf(s, USEC_FMT, when);
+
+        r = device_add_property_internal(device, "USEC_INITIALIZED", s);
+        if (r < 0)
+                return r;
+
+        device->usec_initialized = when;
+        return 0;
+}
+
+static int handle_db_line(sd_device *device, char key, const char *value) {
+        char *path;
+        int r;
+
+        assert(device);
+        assert(value);
+
+        switch (key) {
+        case 'G':
+                r = device_add_tag(device, value);
+                if (r < 0)
+                        return r;
+
+                break;
+        case 'S':
+                path = strjoina("/dev/", value);
+                r = device_add_devlink(device, path);
+                if (r < 0)
+                        return r;
+
+                break;
+        case 'E':
+                r = device_add_property_internal_from_string(device, value);
+                if (r < 0)
+                        return r;
+
+                break;
+        case 'I': {
+                usec_t t;
+
+                r = safe_atou64(value, &t);
+                if (r < 0)
+                        return r;
+
+                r = device_set_usec_initialized(device, t);
+                if (r < 0)
+                        return r;
+
+                break;
+        }
+        case 'L':
+                r = safe_atoi(value, &device->devlink_priority);
+                if (r < 0)
+                        return r;
+
+                break;
+        case 'W':
+                r = safe_atoi(value, &device->watch_handle);
+                if (r < 0)
+                        return r;
+
+                break;
+        default:
+                log_device_debug(device, "sd-device: Unknown key '%c' in device db, ignoring", key);
+        }
+
+        return 0;
+}
+
+int device_get_id_filename(sd_device *device, const char **ret) {
+        assert(device);
+        assert(ret);
+
+        if (!device->id_filename) {
+                _cleanup_free_ char *id = NULL;
+                const char *subsystem;
+                dev_t devnum;
+                int ifindex, r;
+
+                r = sd_device_get_subsystem(device, &subsystem);
+                if (r < 0)
+                        return r;
+
+                if (sd_device_get_devnum(device, &devnum) >= 0) {
+                        assert(subsystem);
+
+                        /* use dev_t — b259:131072, c254:0 */
+                        r = asprintf(&id, "%c%u:%u",
+                                     streq(subsystem, "block") ? 'b' : 'c',
+                                     major(devnum), minor(devnum));
+                        if (r < 0)
+                                return -ENOMEM;
+                } else if (sd_device_get_ifindex(device, &ifindex) >= 0) {
+                        /* use netdev ifindex — n3 */
+                        r = asprintf(&id, "n%u", (unsigned) ifindex);
+                        if (r < 0)
+                                return -ENOMEM;
+                } else {
+                        /* use $subsys:$sysname — pci:0000:00:1f.2
+                         * sysname() has '!' translated, get it from devpath
+                         */
+                        const char *sysname;
+
+                        sysname = basename(device->devpath);
+                        if (!sysname)
+                                return -EINVAL;
+
+                        if (!subsystem)
+                                return -EINVAL;
+
+                        if (streq(subsystem, "drivers")) {
+                                /* the 'drivers' pseudo-subsystem is special, and needs the real subsystem
+                                 * encoded as well */
+                                r = asprintf(&id, "+drivers:%s:%s", device->driver_subsystem, sysname);
+                                if (r < 0)
+                                        return -ENOMEM;
+                        } else {
+                                r = asprintf(&id, "+%s:%s", subsystem, sysname);
+                                if (r < 0)
+                                        return -ENOMEM;
+                        }
+                }
+
+                device->id_filename = TAKE_PTR(id);
+        }
+
+        *ret = device->id_filename;
+        return 0;
+}
+
+int device_read_db_internal(sd_device *device, bool force) {
+        _cleanup_free_ char *db = NULL;
+        char *path;
+        const char *id, *value;
+        char key;
+        size_t db_len;
+        unsigned i;
+        int r;
+
+        enum {
+                PRE_KEY,
+                KEY,
+                PRE_VALUE,
+                VALUE,
+                INVALID_LINE,
+        } state = PRE_KEY;
+
+        assert(device);
+
+        if (device->db_loaded || (!force && device->sealed))
+                return 0;
+
+        r = device_get_id_filename(device, &id);
+        if (r < 0)
+                return r;
+
+        path = strjoina("/run/udev/data/", id);
+
+        r = read_full_file(path, &db, &db_len);
+        if (r < 0) {
+                if (r == -ENOENT)
+                        return 0;
+                else
+                        return log_device_debug_errno(device, r, "sd-device: Failed to read db '%s': %m", path);
+        }
+
+        /* devices with a database entry are initialized */
+        device->is_initialized = true;
+
+        device->db_loaded = true;
+
+        for (i = 0; i < db_len; i++) {
+                switch (state) {
+                case PRE_KEY:
+                        if (!strchr(NEWLINE, db[i])) {
+                                key = db[i];
+
+                                state = KEY;
+                        }
+
+                        break;
+                case KEY:
+                        if (db[i] != ':') {
+                                log_device_debug(device, "sd-device: Invalid db entry with key '%c', ignoring", key);
+
+                                state = INVALID_LINE;
+                        } else {
+                                db[i] = '\0';
+
+                                state = PRE_VALUE;
+                        }
+
+                        break;
+                case PRE_VALUE:
+                        value = &db[i];
+
+                        state = VALUE;
+
+                        break;
+                case INVALID_LINE:
+                        if (strchr(NEWLINE, db[i]))
+                                state = PRE_KEY;
+
+                        break;
+                case VALUE:
+                        if (strchr(NEWLINE, db[i])) {
+                                db[i] = '\0';
+                                r = handle_db_line(device, key, value);
+                                if (r < 0)
+                                        log_device_debug_errno(device, r, "sd-device: Failed to handle db entry '%c:%s', ignoring: %m", key, value);
+
+                                state = PRE_KEY;
+                        }
+
+                        break;
+                default:
+                        assert_not_reached("Invalid state when parsing db");
+                }
+        }
+
+        return 0;
+}
+
+_public_ int sd_device_get_is_initialized(sd_device *device) {
+        int r;
+
+        assert_return(device, -EINVAL);
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        return device->is_initialized;
+}
+
+_public_ int sd_device_get_usec_since_initialized(sd_device *device, uint64_t *usec) {
+        usec_t now_ts;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(usec, -EINVAL);
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        if (!device->is_initialized)
+                return -EBUSY;
+
+        if (!device->usec_initialized)
+                return -ENODATA;
+
+        now_ts = now(clock_boottime_or_monotonic());
+
+        if (now_ts < device->usec_initialized)
+                return -EIO;
+
+        *usec = now_ts - device->usec_initialized;
+        return 0;
+}
+
+_public_ const char *sd_device_get_tag_first(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        device->tags_iterator_generation = device->tags_generation;
+        device->tags_iterator = ITERATOR_FIRST;
+
+        (void) set_iterate(device->tags, &device->tags_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_tag_next(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        if (device->tags_iterator_generation != device->tags_generation)
+                return NULL;
+
+        (void) set_iterate(device->tags, &device->tags_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_devlink_first(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        device->devlinks_iterator_generation = device->devlinks_generation;
+        device->devlinks_iterator = ITERATOR_FIRST;
+
+        (void) set_iterate(device->devlinks, &device->devlinks_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_devlink_next(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        (void) device_read_db(device);
+
+        if (device->devlinks_iterator_generation != device->devlinks_generation)
+                return NULL;
+
+        (void) set_iterate(device->devlinks, &device->devlinks_iterator, &v);
+        return v;
+}
+
+int device_properties_prepare(sd_device *device) {
+        int r;
+
+        assert(device);
+
+        r = device_read_uevent_file(device);
+        if (r < 0)
+                return r;
+
+        r = device_read_db(device);
+        if (r < 0)
+                return r;
+
+        if (device->property_devlinks_outdated) {
+                _cleanup_free_ char *devlinks = NULL;
+                size_t devlinks_allocated = 0, devlinks_len = 0;
+                const char *devlink;
+
+                for (devlink = sd_device_get_devlink_first(device); devlink; devlink = sd_device_get_devlink_next(device)) {
+                        char *e;
+
+                        if (!GREEDY_REALLOC(devlinks, devlinks_allocated, devlinks_len + strlen(devlink) + 2))
+                                return -ENOMEM;
+                        if (devlinks_len > 0)
+                                stpcpy(devlinks + devlinks_len++, " ");
+                        e = stpcpy(devlinks + devlinks_len, devlink);
+                        devlinks_len = e - devlinks;
+                }
+
+                r = device_add_property_internal(device, "DEVLINKS", devlinks);
+                if (r < 0)
+                        return r;
+
+                device->property_devlinks_outdated = false;
+        }
+
+        if (device->property_tags_outdated) {
+                _cleanup_free_ char *tags = NULL;
+                size_t tags_allocated = 0, tags_len = 0;
+                const char *tag;
+
+                if (!GREEDY_REALLOC(tags, tags_allocated, 2))
+                        return -ENOMEM;
+                stpcpy(tags, ":");
+                tags_len++;
+
+                for (tag = sd_device_get_tag_first(device); tag; tag = sd_device_get_tag_next(device)) {
+                        char *e;
+
+                        if (!GREEDY_REALLOC(tags, tags_allocated, tags_len + strlen(tag) + 2))
+                                return -ENOMEM;
+                        e = stpcpy(stpcpy(tags + tags_len, tag), ":");
+                        tags_len = e - tags;
+                }
+
+                r = device_add_property_internal(device, "TAGS", tags);
+                if (r < 0)
+                        return r;
+
+                device->property_tags_outdated = false;
+        }
+
+        return 0;
+}
+
+_public_ const char *sd_device_get_property_first(sd_device *device, const char **_value) {
+        const char *key;
+        const char *value;
+        int r;
+
+        assert_return(device, NULL);
+
+        r = device_properties_prepare(device);
+        if (r < 0)
+                return NULL;
+
+        device->properties_iterator_generation = device->properties_generation;
+        device->properties_iterator = ITERATOR_FIRST;
+
+        ordered_hashmap_iterate(device->properties, &device->properties_iterator, (void**)&value, (const void**)&key);
+
+        if (_value)
+                *_value = value;
+        return key;
+}
+
+_public_ const char *sd_device_get_property_next(sd_device *device, const char **_value) {
+        const char *key;
+        const char *value;
+        int r;
+
+        assert_return(device, NULL);
+
+        r = device_properties_prepare(device);
+        if (r < 0)
+                return NULL;
+
+        if (device->properties_iterator_generation != device->properties_generation)
+                return NULL;
+
+        ordered_hashmap_iterate(device->properties, &device->properties_iterator, (void**)&value, (const void**)&key);
+
+        if (_value)
+                *_value = value;
+        return key;
+}
+
+static int device_sysattrs_read_all(sd_device *device) {
+        _cleanup_closedir_ DIR *dir = NULL;
+        const char *syspath;
+        struct dirent *dent;
+        int r;
+
+        assert(device);
+
+        if (device->sysattrs_read)
+                return 0;
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        dir = opendir(syspath);
+        if (!dir)
+                return -errno;
+
+        r = set_ensure_allocated(&device->sysattrs, &string_hash_ops);
+        if (r < 0)
+                return r;
+
+        FOREACH_DIRENT_ALL(dent, dir, return -errno) {
+                char *path;
+                struct stat statbuf;
+
+                /* only handle symlinks and regular files */
+                if (!IN_SET(dent->d_type, DT_LNK, DT_REG))
+                        continue;
+
+                path = strjoina(syspath, "/", dent->d_name);
+
+                if (lstat(path, &statbuf) != 0)
+                        continue;
+
+                if (!(statbuf.st_mode & S_IRUSR))
+                        continue;
+
+                r = set_put_strdup(device->sysattrs, dent->d_name);
+                if (r < 0)
+                        return r;
+        }
+
+        device->sysattrs_read = true;
+
+        return 0;
+}
+
+_public_ const char *sd_device_get_sysattr_first(sd_device *device) {
+        void *v;
+        int r;
+
+        assert_return(device, NULL);
+
+        if (!device->sysattrs_read) {
+                r = device_sysattrs_read_all(device);
+                if (r < 0) {
+                        errno = -r;
+                        return NULL;
+                }
+        }
+
+        device->sysattrs_iterator = ITERATOR_FIRST;
+
+        (void) set_iterate(device->sysattrs, &device->sysattrs_iterator, &v);
+        return v;
+}
+
+_public_ const char *sd_device_get_sysattr_next(sd_device *device) {
+        void *v;
+
+        assert_return(device, NULL);
+
+        if (!device->sysattrs_read)
+                return NULL;
+
+        (void) set_iterate(device->sysattrs, &device->sysattrs_iterator, &v);
+        return v;
+}
+
+_public_ int sd_device_has_tag(sd_device *device, const char *tag) {
+        assert_return(device, -EINVAL);
+        assert_return(tag, -EINVAL);
+
+        (void) device_read_db(device);
+
+        return !!set_contains(device->tags, tag);
+}
+
+_public_ int sd_device_get_property_value(sd_device *device, const char *key, const char **_value) {
+        char *value;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(key, -EINVAL);
+
+        r = device_properties_prepare(device);
+        if (r < 0)
+                return r;
+
+        value = ordered_hashmap_get(device->properties, key);
+        if (!value)
+                return -ENOENT;
+
+        if (_value)
+                *_value = value;
+        return 0;
+}
+
+/* replaces the value if it already exists */
+static int device_add_sysattr_value(sd_device *device, const char *_key, char *value) {
+        _cleanup_free_ char *key = NULL;
+        _cleanup_free_ char *value_old = NULL;
+        int r;
+
+        assert(device);
+        assert(_key);
+
+        r = hashmap_ensure_allocated(&device->sysattr_values, &string_hash_ops);
+        if (r < 0)
+                return r;
+
+        value_old = hashmap_remove2(device->sysattr_values, _key, (void **)&key);
+        if (!key) {
+                key = strdup(_key);
+                if (!key)
+                        return -ENOMEM;
+        }
+
+        r = hashmap_put(device->sysattr_values, key, value);
+        if (r < 0)
+                return r;
+        TAKE_PTR(key);
+
+        return 0;
+}
+
+static int device_get_sysattr_value(sd_device *device, const char *_key, const char **_value) {
+        const char *key = NULL, *value;
+
+        assert(device);
+        assert(_key);
+
+        value = hashmap_get2(device->sysattr_values, _key, (void **) &key);
+        if (!key)
+                return -ENOENT;
+
+        if (_value)
+                *_value = value;
+        return 0;
+}
+
+/* We cache all sysattr lookups. If an attribute does not exist, it is stored
+ * with a NULL value in the cache, otherwise the returned string is stored */
+_public_ int sd_device_get_sysattr_value(sd_device *device, const char *sysattr, const char **_value) {
+        _cleanup_free_ char *value = NULL;
+        const char *syspath, *cached_value = NULL;
+        char *path;
+        struct stat statbuf;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(sysattr, -EINVAL);
+
+        /* look for possibly already cached result */
+        r = device_get_sysattr_value(device, sysattr, &cached_value);
+        if (r != -ENOENT) {
+                if (r < 0)
+                        return r;
+
+                if (!cached_value)
+                        /* we looked up the sysattr before and it did not exist */
+                        return -ENOENT;
+
+                if (_value)
+                        *_value = cached_value;
+
+                return 0;
+        }
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        path = strjoina(syspath, "/", sysattr);
+        r = lstat(path, &statbuf);
+        if (r < 0) {
+                /* remember that we could not access the sysattr */
+                r = device_add_sysattr_value(device, sysattr, NULL);
+                if (r < 0)
+                        return r;
+
+                return -ENOENT;
+        } else if (S_ISLNK(statbuf.st_mode)) {
+                /* Some core links return only the last element of the target path,
+                 * these are just values, the paths should not be exposed. */
+                if (STR_IN_SET(sysattr, "driver", "subsystem", "module")) {
+                        r = readlink_value(path, &value);
+                        if (r < 0)
+                                return r;
+                } else
+                        return -EINVAL;
+        } else if (S_ISDIR(statbuf.st_mode)) {
+                /* skip directories */
+                return -EINVAL;
+        } else if (!(statbuf.st_mode & S_IRUSR)) {
+                /* skip non-readable files */
+                return -EPERM;
+        } else {
+                size_t size;
+
+                /* read attribute value */
+                r = read_full_file(path, &value, &size);
+                if (r < 0)
+                        return r;
+
+                /* drop trailing newlines */
+                while (size > 0 && value[--size] == '\n')
+                        value[size] = '\0';
+        }
+
+        r = device_add_sysattr_value(device, sysattr, value);
+        if (r < 0)
+                return r;
+
+        *_value = TAKE_PTR(value);
+
+        return 0;
+}
+
+static void device_remove_sysattr_value(sd_device *device, const char *_key) {
+        _cleanup_free_ char *key = NULL;
+
+        assert(device);
+        assert(_key);
+
+        free(hashmap_remove2(device->sysattr_values, _key, (void **) &key));
+}
+
+/* set the attribute and save it in the cache. If a NULL value is passed the
+ * attribute is cleared from the cache */
+_public_ int sd_device_set_sysattr_value(sd_device *device, const char *sysattr, const char *_value) {
+        _cleanup_free_ char *value = NULL;
+        const char *syspath, *path;
+        size_t len;
+        int r;
+
+        assert_return(device, -EINVAL);
+        assert_return(sysattr, -EINVAL);
+
+        if (!_value) {
+                device_remove_sysattr_value(device, sysattr);
+                return 0;
+        }
+
+        r = sd_device_get_syspath(device, &syspath);
+        if (r < 0)
+                return r;
+
+        path = strjoina(syspath, "/", sysattr);
+
+        len = strlen(_value);
+
+        /* drop trailing newlines */
+        while (len > 0 && _value[len - 1] == '\n')
+                len --;
+
+        /* value length is limited to 4k */
+        if (len > 4096)
+                return -EINVAL;
+
+        value = strndup(_value, len);
+        if (!value)
+                return -ENOMEM;
+
+        r = write_string_file(path, value, WRITE_STRING_FILE_DISABLE_BUFFER | WRITE_STRING_FILE_NOFOLLOW);
+        if (r < 0) {
+                if (r == -ELOOP)
+                        return -EINVAL;
+                if (r == -EISDIR)
+                        return r;
+
+                r = free_and_strdup(&value, "");
+                if (r < 0)
+                        return r;
+
+                r = device_add_sysattr_value(device, sysattr, value);
+                if (r < 0)
+                        return r;
+                TAKE_PTR(value);
+
+                return -ENXIO;
+        }
+
+        r = device_add_sysattr_value(device, sysattr, value);
+        if (r < 0)
+                return r;
+        TAKE_PTR(value);
+
+        return 0;
+}