Adding upstream version 255.4.upstream/255.4

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

1 files changed, 896 insertions, 0 deletions

diff --git a/src/udev/udev-builtin-path_id.c b/src/udev/udev-builtin-path_id.c
new file mode 100644
index 0000000..467c9a6
--- /dev/null
+++ b/src/udev/udev-builtin-path_id.c
@@ -0,0 +1,896 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * compose persistent device path
+ *
+ * Logic based on Hannes Reinecke's shell script.
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <linux/usb/ch11.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "device-util.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "parse-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "sysexits.h"
+#include "udev-builtin.h"
+#include "udev-util.h"
+
+_printf_(2,3)
+static void path_prepend(char **path, const char *fmt, ...) {
+        va_list va;
+        _cleanup_free_ char *pre = NULL;
+        int r;
+
+        va_start(va, fmt);
+        r = vasprintf(&pre, fmt, va);
+        va_end(va);
+        if (r < 0) {
+                log_oom();
+                exit(EX_OSERR);
+        }
+
+        if (*path) {
+                char *new;
+
+                new = strjoin(pre, "-", *path);
+                if (!new) {
+                        log_oom();
+                        exit(EX_OSERR);
+                }
+
+                free_and_replace(*path, new);
+        } else
+                *path = TAKE_PTR(pre);
+}
+
+/*
+** Linux only supports 32 bit luns.
+** See drivers/scsi/scsi_scan.c::scsilun_to_int() for more details.
+*/
+static int format_lun_number(sd_device *dev, char **path) {
+        const char *sysnum;
+        unsigned long lun;
+        int r;
+
+        r = sd_device_get_sysnum(dev, &sysnum);
+        if (r < 0)
+                return r;
+        if (!sysnum)
+                return -ENOENT;
+
+        r = safe_atolu_full(sysnum, 10, &lun);
+        if (r < 0)
+                return r;
+        if (lun < 256)
+                /* address method 0, peripheral device addressing with bus id of zero */
+                path_prepend(path, "lun-%lu", lun);
+        else
+                /* handle all other lun addressing methods by using a variant of the original lun format */
+                path_prepend(path, "lun-0x%04lx%04lx00000000", lun & 0xffff, (lun >> 16) & 0xffff);
+
+        return 0;
+}
+
+static sd_device *skip_subsystem(sd_device *dev, const char *subsys) {
+        sd_device *parent;
+
+        assert(dev);
+        assert(subsys);
+
+        /* Unlike the function name, this drops multiple parent devices EXCEPT FOR THE LAST ONE.
+         * The last one will be dropped at the end of the loop in builtin_path_id().
+         * E.g.
+         * Input:  /sys/devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1:1.0
+         * Output: /sys/devices/pci0000:00/0000:00:14.0/usb1
+         */
+
+        for (parent = dev; ; ) {
+                const char *subsystem;
+
+                if (sd_device_get_subsystem(parent, &subsystem) < 0)
+                        break;
+
+                if (!streq(subsystem, subsys))
+                        break;
+
+                dev = parent;
+                if (sd_device_get_parent(dev, &parent) < 0)
+                        break;
+        }
+
+        return dev;
+}
+
+static sd_device *handle_scsi_fibre_channel(sd_device *parent, char **path) {
+        sd_device *targetdev;
+        _cleanup_(sd_device_unrefp) sd_device *fcdev = NULL;
+        const char *port, *sysname;
+        _cleanup_free_ char *lun = NULL;
+
+        assert(parent);
+        assert(path);
+
+        if (sd_device_get_parent_with_subsystem_devtype(parent, "scsi", "scsi_target", &targetdev) < 0)
+                return NULL;
+        if (sd_device_get_sysname(targetdev, &sysname) < 0)
+                return NULL;
+        if (sd_device_new_from_subsystem_sysname(&fcdev, "fc_transport", sysname) < 0)
+                return NULL;
+        if (sd_device_get_sysattr_value(fcdev, "port_name", &port) < 0)
+                return NULL;
+
+        format_lun_number(parent, &lun);
+        path_prepend(path, "fc-%s-%s", port, lun);
+        return parent;
+}
+
+static sd_device *handle_scsi_sas_wide_port(sd_device *parent, char **path) {
+        sd_device *targetdev, *target_parent;
+        _cleanup_(sd_device_unrefp) sd_device *sasdev = NULL;
+        const char *sas_address, *sysname;
+        _cleanup_free_ char *lun = NULL;
+
+        assert(parent);
+        assert(path);
+
+        if (sd_device_get_parent_with_subsystem_devtype(parent, "scsi", "scsi_target", &targetdev) < 0)
+                return NULL;
+        if (sd_device_get_parent(targetdev, &target_parent) < 0)
+                return NULL;
+        if (sd_device_get_sysname(target_parent, &sysname) < 0)
+                return NULL;
+        if (sd_device_new_from_subsystem_sysname(&sasdev, "sas_device", sysname) < 0)
+                return NULL;
+        if (sd_device_get_sysattr_value(sasdev, "sas_address", &sas_address) < 0)
+                return NULL;
+
+        format_lun_number(parent, &lun);
+        path_prepend(path, "sas-%s-%s", sas_address, lun);
+        return parent;
+}
+
+static sd_device *handle_scsi_sas(sd_device *parent, char **path) {
+        sd_device *targetdev, *target_parent, *port, *expander;
+        _cleanup_(sd_device_unrefp) sd_device *target_sasdev = NULL, *expander_sasdev = NULL, *port_sasdev = NULL;
+        const char *sas_address = NULL;
+        const char *phy_id;
+        const char *phy_count, *sysname;
+        _cleanup_free_ char *lun = NULL;
+
+        assert(parent);
+        assert(path);
+
+        if (sd_device_get_parent_with_subsystem_devtype(parent, "scsi", "scsi_target", &targetdev) < 0)
+                return NULL;
+        if (sd_device_get_parent(targetdev, &target_parent) < 0)
+                return NULL;
+        if (sd_device_get_sysname(target_parent, &sysname) < 0)
+                return NULL;
+        /* Get sas device */
+        if (sd_device_new_from_subsystem_sysname(&target_sasdev, "sas_device", sysname) < 0)
+                return NULL;
+        /* The next parent is sas port */
+        if (sd_device_get_parent(target_parent, &port) < 0)
+                return NULL;
+        if (sd_device_get_sysname(port, &sysname) < 0)
+                return NULL;
+        /* Get port device */
+        if (sd_device_new_from_subsystem_sysname(&port_sasdev, "sas_port", sysname) < 0)
+                return NULL;
+        if (sd_device_get_sysattr_value(port_sasdev, "num_phys", &phy_count) < 0)
+                return NULL;
+
+        /* Check if we are simple disk */
+        if (strncmp(phy_count, "1", 2) != 0)
+                return handle_scsi_sas_wide_port(parent, path);
+
+        /* Get connected phy */
+        if (sd_device_get_sysattr_value(target_sasdev, "phy_identifier", &phy_id) < 0)
+                return NULL;
+
+        /* The port's parent is either hba or expander */
+        if (sd_device_get_parent(port, &expander) < 0)
+                return NULL;
+
+        if (sd_device_get_sysname(expander, &sysname) < 0)
+                return NULL;
+        /* Get expander device */
+        if (sd_device_new_from_subsystem_sysname(&expander_sasdev, "sas_device", sysname) >= 0) {
+                /* Get expander's address */
+                if (sd_device_get_sysattr_value(expander_sasdev, "sas_address", &sas_address) < 0)
+                        return NULL;
+        }
+
+        format_lun_number(parent, &lun);
+        if (sas_address)
+                 path_prepend(path, "sas-exp%s-phy%s-%s", sas_address, phy_id, lun);
+        else
+                 path_prepend(path, "sas-phy%s-%s", phy_id, lun);
+
+        return parent;
+}
+
+static sd_device *handle_scsi_iscsi(sd_device *parent, char **path) {
+        sd_device *transportdev;
+        _cleanup_(sd_device_unrefp) sd_device *sessiondev = NULL, *conndev = NULL;
+        const char *target, *connname, *addr, *port;
+        _cleanup_free_ char *lun = NULL;
+        const char *sysname, *sysnum;
+
+        assert(parent);
+        assert(path);
+
+        /* find iscsi session */
+        for (transportdev = parent; ; ) {
+
+                if (sd_device_get_parent(transportdev, &transportdev) < 0)
+                        return NULL;
+                if (sd_device_get_sysname(transportdev, &sysname) < 0)
+                        return NULL;
+                if (startswith(sysname, "session"))
+                        break;
+        }
+
+        /* find iscsi session device */
+        if (sd_device_new_from_subsystem_sysname(&sessiondev, "iscsi_session", sysname) < 0)
+                return NULL;
+
+        if (sd_device_get_sysattr_value(sessiondev, "targetname", &target) < 0)
+                return NULL;
+
+        if (sd_device_get_sysnum(transportdev, &sysnum) < 0 || !sysnum)
+                return NULL;
+        connname = strjoina("connection", sysnum, ":0");
+        if (sd_device_new_from_subsystem_sysname(&conndev, "iscsi_connection", connname) < 0)
+                return NULL;
+
+        if (sd_device_get_sysattr_value(conndev, "persistent_address", &addr) < 0)
+                return NULL;
+        if (sd_device_get_sysattr_value(conndev, "persistent_port", &port) < 0)
+                return NULL;
+
+        format_lun_number(parent, &lun);
+        path_prepend(path, "ip-%s:%s-iscsi-%s-%s", addr, port, target, lun);
+        return parent;
+}
+
+static sd_device *handle_scsi_ata(sd_device *parent, char **path, char **compat_path) {
+        sd_device *targetdev, *target_parent;
+        _cleanup_(sd_device_unrefp) sd_device *atadev = NULL;
+        const char *port_no, *sysname, *name;
+        unsigned host, bus, target, lun;
+
+        assert(parent);
+        assert(path);
+
+        if (sd_device_get_sysname(parent, &name) < 0)
+                return NULL;
+        if (sscanf(name, "%u:%u:%u:%u", &host, &bus, &target, &lun) != 4)
+                return NULL;
+
+        if (sd_device_get_parent_with_subsystem_devtype(parent, "scsi", "scsi_host", &targetdev) < 0)
+                return NULL;
+
+        if (sd_device_get_parent(targetdev, &target_parent) < 0)
+                return NULL;
+
+        if (sd_device_get_sysname(target_parent, &sysname) < 0)
+                return NULL;
+        if (sd_device_new_from_subsystem_sysname(&atadev, "ata_port", sysname) < 0)
+                return NULL;
+
+        if (sd_device_get_sysattr_value(atadev, "port_no", &port_no) < 0)
+                return NULL;
+
+        if (bus != 0)
+                /* Devices behind port multiplier have a bus != 0 */
+                path_prepend(path, "ata-%s.%u.0", port_no, bus);
+        else
+                /* Master/slave are distinguished by target id */
+                path_prepend(path, "ata-%s.%u", port_no, target);
+
+        /* old compatible persistent link for ATA devices */
+        if (compat_path)
+                path_prepend(compat_path, "ata-%s", port_no);
+
+        return parent;
+}
+
+static sd_device *handle_scsi_default(sd_device *parent, char **path) {
+        sd_device *hostdev;
+        int host, bus, target, lun;
+        const char *name, *base, *pos;
+        _cleanup_closedir_ DIR *dir = NULL;
+        int basenum = -1;
+
+        assert(parent);
+        assert(path);
+
+        if (sd_device_get_parent_with_subsystem_devtype(parent, "scsi", "scsi_host", &hostdev) < 0)
+                return NULL;
+
+        if (sd_device_get_sysname(parent, &name) < 0)
+                return NULL;
+        if (sscanf(name, "%d:%d:%d:%d", &host, &bus, &target, &lun) != 4)
+                return NULL;
+
+        /*
+         * Rebase host offset to get the local relative number
+         *
+         * Note: This is by definition racy, unreliable and too simple.
+         * Please do not copy this model anywhere. It's just a left-over
+         * from the time we had no idea how things should look like in
+         * the end.
+         *
+         * Making assumptions about a global in-kernel counter and use
+         * that to calculate a local offset is a very broken concept. It
+         * can only work as long as things are in strict order.
+         *
+         * The kernel needs to export the instance/port number of a
+         * controller directly, without the need for rebase magic like
+         * this. Manual driver unbind/bind, parallel hotplug/unplug will
+         * get into the way of this "I hope it works" logic.
+         */
+
+        if (sd_device_get_syspath(hostdev, &base) < 0)
+                return NULL;
+        pos = strrchr(base, '/');
+        if (!pos)
+                return NULL;
+
+        base = strndupa_safe(base, pos - base);
+        dir = opendir(base);
+        if (!dir)
+                return NULL;
+
+        FOREACH_DIRENT_ALL(de, dir, break) {
+                unsigned i;
+
+                if (de->d_name[0] == '.')
+                        continue;
+                if (!IN_SET(de->d_type, DT_DIR, DT_LNK))
+                        continue;
+                if (!startswith(de->d_name, "host"))
+                        continue;
+                if (safe_atou_full(&de->d_name[4], 10, &i) < 0)
+                        continue;
+                /*
+                 * find the smallest number; the host really needs to export its
+                 * own instance number per parent device; relying on the global host
+                 * enumeration and plainly rebasing the numbers sounds unreliable
+                 */
+                if (basenum == -1 || (int) i < basenum)
+                        basenum = i;
+        }
+        if (basenum == -1)
+                return hostdev;
+        host -= basenum;
+
+        path_prepend(path, "scsi-%i:%i:%i:%i", host, bus, target, lun);
+        return hostdev;
+}
+
+static sd_device *handle_scsi_hyperv(sd_device *parent, char **path, size_t guid_str_len) {
+        sd_device *hostdev;
+        sd_device *vmbusdev;
+        const char *guid_str;
+        _cleanup_free_ char *lun = NULL;
+        char guid[39];
+
+        assert(parent);
+        assert(path);
+        assert(guid_str_len < sizeof(guid));
+
+        if (sd_device_get_parent_with_subsystem_devtype(parent, "scsi", "scsi_host", &hostdev) < 0)
+                return NULL;
+
+        if (sd_device_get_parent(hostdev, &vmbusdev) < 0)
+                return NULL;
+
+        if (sd_device_get_sysattr_value(vmbusdev, "device_id", &guid_str) < 0)
+                return NULL;
+
+        if (strlen(guid_str) < guid_str_len || guid_str[0] != '{' || guid_str[guid_str_len-1] != '}')
+                return NULL;
+
+        size_t k = 0;
+        for (size_t i = 1; i < guid_str_len-1; i++) {
+                if (guid_str[i] == '-')
+                        continue;
+                guid[k++] = guid_str[i];
+        }
+        guid[k] = '\0';
+
+        format_lun_number(parent, &lun);
+        path_prepend(path, "vmbus-%s-%s", guid, lun);
+        return parent;
+}
+
+static sd_device *handle_scsi(sd_device *parent, char **path, char **compat_path, bool *supported_parent) {
+        const char *devtype, *id, *name;
+
+        if (sd_device_get_devtype(parent, &devtype) < 0 ||
+            !streq(devtype, "scsi_device"))
+                return parent;
+
+        /* firewire */
+        if (sd_device_get_sysattr_value(parent, "ieee1394_id", &id) >= 0) {
+                path_prepend(path, "ieee1394-0x%s", id);
+                *supported_parent = true;
+                return skip_subsystem(parent, "scsi");
+        }
+
+        /* scsi sysfs does not have a "subsystem" for the transport */
+        if (sd_device_get_syspath(parent, &name) < 0)
+                return NULL;
+
+        if (strstr(name, "/rport-")) {
+                *supported_parent = true;
+                return handle_scsi_fibre_channel(parent, path);
+        }
+
+        if (strstr(name, "/end_device-")) {
+                *supported_parent = true;
+                return handle_scsi_sas(parent, path);
+        }
+
+        if (strstr(name, "/session")) {
+                *supported_parent = true;
+                return handle_scsi_iscsi(parent, path);
+        }
+
+        if (strstr(name, "/ata"))
+                return handle_scsi_ata(parent, path, compat_path);
+
+        if (strstr(name, "/vmbus_"))
+                return handle_scsi_hyperv(parent, path, 37);
+        else if (strstr(name, "/VMBUS"))
+                return handle_scsi_hyperv(parent, path, 38);
+
+        return handle_scsi_default(parent, path);
+}
+
+static sd_device *handle_cciss(sd_device *parent, char **path) {
+        const char *str;
+        unsigned controller, disk;
+
+        if (sd_device_get_sysname(parent, &str) < 0)
+                return NULL;
+        if (sscanf(str, "c%ud%u%*s", &controller, &disk) != 2)
+                return NULL;
+
+        path_prepend(path, "cciss-disk%u", disk);
+        return skip_subsystem(parent, "cciss");
+}
+
+static void handle_scsi_tape(sd_device *dev, char **path) {
+        const char *name;
+
+        /* must be the last device in the syspath */
+        if (*path)
+                return;
+
+        if (sd_device_get_sysname(dev, &name) < 0)
+                return;
+
+        if (startswith(name, "nst") && strchr("lma", name[3]))
+                path_prepend(path, "nst%c", name[3]);
+        else if (startswith(name, "st") && strchr("lma", name[2]))
+                path_prepend(path, "st%c", name[2]);
+}
+
+static int get_usb_revision(sd_device *dev) {
+        uint8_t protocol;
+        const char *s;
+        int r;
+
+        assert(dev);
+
+        /* Returns usb revision 1, 2, or 3. */
+
+        r = sd_device_get_sysattr_value(dev, "bDeviceProtocol", &s);
+        if (r < 0)
+                return r;
+
+        r = safe_atou8_full(s, 16, &protocol);
+        if (r < 0)
+                return r;
+
+        switch (protocol) {
+        case USB_HUB_PR_HS_NO_TT: /* Full speed hub (USB1) or Hi-speed hub without TT (USB2) */
+
+                /* See speed_show() in drivers/usb/core/sysfs.c of the kernel. */
+                r = sd_device_get_sysattr_value(dev, "speed", &s);
+                if (r < 0)
+                        return r;
+
+                if (streq(s, "480"))
+                        return 2;
+
+                return 1;
+
+        case USB_HUB_PR_HS_SINGLE_TT: /* Hi-speed hub with single TT */
+        case USB_HUB_PR_HS_MULTI_TT: /* Hi-speed hub with multiple TT */
+                return 2;
+
+        case USB_HUB_PR_SS: /* Super speed hub */
+                return 3;
+
+        default:
+                return -EPROTONOSUPPORT;
+        }
+}
+
+static sd_device *handle_usb(sd_device *parent, char **path) {
+        const char *devtype, *str, *port;
+        int r;
+
+        if (sd_device_get_devtype(parent, &devtype) < 0)
+                return parent;
+        if (!STR_IN_SET(devtype, "usb_interface", "usb_device"))
+                return parent;
+
+        if (sd_device_get_sysname(parent, &str) < 0)
+                return parent;
+        port = strchr(str, '-');
+        if (!port)
+                return parent;
+        port++;
+
+        parent = skip_subsystem(parent, "usb");
+        if (!parent)
+                return NULL;
+
+        /* USB host number may change across reboots (and probably even without reboot). The part after USB
+         * host number is determined by device topology and so does not change. Hence, drop the host number
+         * and always use '0' instead.
+         *
+         * xHCI host controllers may register two (or more?) USB root hubs for USB 2.0 and USB 3.0, and the
+         * sysname, whose host number replaced with 0, of a device under the hubs may conflict with others.
+         * To avoid the conflict, let's include the USB revision of the root hub to the PATH_ID.
+         * See issue https://github.com/systemd/systemd/issues/19406 for more details. */
+        r = get_usb_revision(parent);
+        if (r < 0) {
+                log_device_debug_errno(parent, r, "Failed to get the USB revision number, ignoring: %m");
+                path_prepend(path, "usb-0:%s", port);
+        } else {
+                assert(r > 0);
+                path_prepend(path, "usbv%i-0:%s", r, port);
+        }
+
+        return parent;
+}
+
+static sd_device *handle_bcma(sd_device *parent, char **path) {
+        const char *sysname;
+        unsigned core;
+
+        if (sd_device_get_sysname(parent, &sysname) < 0)
+                return NULL;
+        if (sscanf(sysname, "bcma%*u:%u", &core) != 1)
+                return NULL;
+
+        path_prepend(path, "bcma-%u", core);
+        return parent;
+}
+
+/* Handle devices of AP bus in System z platform. */
+static sd_device *handle_ap(sd_device *parent, char **path) {
+        const char *type, *func;
+
+        assert(parent);
+        assert(path);
+
+        if (sd_device_get_sysattr_value(parent, "type", &type) >= 0 &&
+            sd_device_get_sysattr_value(parent, "ap_functions", &func) >= 0)
+                path_prepend(path, "ap-%s-%s", type, func);
+        else {
+                const char *sysname;
+
+                if (sd_device_get_sysname(parent, &sysname) >= 0)
+                        path_prepend(path, "ap-%s", sysname);
+        }
+
+        return skip_subsystem(parent, "ap");
+}
+
+static int find_real_nvme_parent(sd_device *dev, sd_device **ret) {
+        _cleanup_(sd_device_unrefp) sd_device *nvme = NULL;
+        const char *sysname, *end, *devpath;
+        int r;
+
+        /* If the device belongs to "nvme-subsystem" (not to be confused with "nvme"), which happens when
+         * NVMe multipathing is enabled in the kernel (/sys/module/nvme_core/parameters/multipath is Y),
+         * then the syspath is something like the following:
+         *   /sys/devices/virtual/nvme-subsystem/nvme-subsys0/nvme0n1
+         * Hence, we need to find the 'real parent' in "nvme" subsystem, e.g,
+         *   /sys/devices/pci0000:00/0000:00:1c.4/0000:3c:00.0/nvme/nvme0 */
+
+        assert(dev);
+        assert(ret);
+
+        r = sd_device_get_sysname(dev, &sysname);
+        if (r < 0)
+                return r;
+
+        /* The sysname format of nvme block device is nvme%d[c%d]n%d[p%d], e.g. nvme0n1p2 or nvme0c1n2.
+         * (Note, nvme device with 'c' can be ignored, as they are hidden. )
+         * The sysname format of nvme subsystem device is nvme%d.
+         * See nvme_alloc_ns() and nvme_init_ctrl() in drivers/nvme/host/core.c for more details. */
+        end = startswith(sysname, "nvme");
+        if (!end)
+                return -ENXIO;
+
+        end += strspn(end, DIGITS);
+        sysname = strndupa(sysname, end - sysname);
+
+        r = sd_device_new_from_subsystem_sysname(&nvme, "nvme", sysname);
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_devpath(nvme, &devpath);
+        if (r < 0)
+                return r;
+
+        /* If the 'real parent' is (still) virtual, e.g. for nvmf disks, refuse to set ID_PATH. */
+        if (path_startswith(devpath, "/devices/virtual/"))
+                return -ENXIO;
+
+        *ret = TAKE_PTR(nvme);
+        return 0;
+}
+
+static void add_id_with_usb_revision(sd_device *dev, bool test, char *path) {
+        char *p;
+        int r;
+
+        assert(dev);
+        assert(path);
+
+        /* When the path contains the USB revision, let's adds ID_PATH_WITH_USB_REVISION property and
+         * drop the version specifier for later use. */
+
+        p = strstrafter(path, "-usbv");
+        if (!p)
+                return;
+        if (!ascii_isdigit(p[0]))
+                return;
+        if (p[1] != '-')
+                return;
+
+        r = udev_builtin_add_property(dev, test, "ID_PATH_WITH_USB_REVISION", path);
+        if (r < 0)
+                log_device_debug_errno(dev, r, "Failed to add ID_PATH_WITH_USB_REVISION property, ignoring: %m");
+
+        /* Drop the USB revision specifier for backward compatibility. */
+        memmove(p - 1, p + 1, strlen(p + 1) + 1);
+}
+
+static void add_id_tag(sd_device *dev, bool test, const char *path) {
+        char tag[UDEV_NAME_SIZE];
+        size_t i = 0;
+        int r;
+
+        /* compose valid udev tag name */
+        for (const char *p = path; *p; p++) {
+                if (ascii_isdigit(*p) ||
+                    ascii_isalpha(*p) ||
+                    *p == '-') {
+                        tag[i++] = *p;
+                        continue;
+                }
+
+                /* skip all leading '_' */
+                if (i == 0)
+                        continue;
+
+                /* avoid second '_' */
+                if (tag[i-1] == '_')
+                        continue;
+
+                tag[i++] = '_';
+        }
+        /* strip trailing '_' */
+        while (i > 0 && tag[i-1] == '_')
+                i--;
+        tag[i] = '\0';
+
+        r = udev_builtin_add_property(dev, test, "ID_PATH_TAG", tag);
+        if (r < 0)
+                log_device_debug_errno(dev, r, "Failed to add ID_PATH_TAG property, ignoring: %m");
+}
+
+static int builtin_path_id(UdevEvent *event, int argc, char *argv[], bool test) {
+        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
+        _cleanup_(sd_device_unrefp) sd_device *dev_other_branch = NULL;
+        _cleanup_free_ char *path = NULL, *compat_path = NULL;
+        bool supported_transport = false, supported_parent = false;
+        const char *subsystem;
+        int r;
+
+        /* walk up the chain of devices and compose path */
+        for (sd_device *parent = dev; parent; ) {
+                const char *subsys, *sysname;
+
+                if (sd_device_get_subsystem(parent, &subsys) < 0 ||
+                    sd_device_get_sysname(parent, &sysname) < 0) {
+                        ;
+                } else if (streq(subsys, "scsi_tape")) {
+                        handle_scsi_tape(parent, &path);
+                } else if (streq(subsys, "scsi")) {
+                        parent = handle_scsi(parent, &path, &compat_path, &supported_parent);
+                        supported_transport = true;
+                } else if (streq(subsys, "cciss")) {
+                        parent = handle_cciss(parent, &path);
+                        supported_transport = true;
+                } else if (streq(subsys, "usb")) {
+                        parent = handle_usb(parent, &path);
+                        supported_transport = true;
+                } else if (streq(subsys, "bcma")) {
+                        parent = handle_bcma(parent, &path);
+                        supported_transport = true;
+                } else if (streq(subsys, "serio")) {
+                        const char *sysnum;
+
+                        if (sd_device_get_sysnum(parent, &sysnum) >= 0 && sysnum) {
+                                path_prepend(&path, "serio-%s", sysnum);
+                                parent = skip_subsystem(parent, "serio");
+                        }
+                } else if (streq(subsys, "pci")) {
+                        path_prepend(&path, "pci-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "pci-%s", sysname);
+                        parent = skip_subsystem(parent, "pci");
+                        supported_parent = true;
+                } else if (streq(subsys, "platform")) {
+                        path_prepend(&path, "platform-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "platform-%s", sysname);
+                        parent = skip_subsystem(parent, "platform");
+                        supported_transport = true;
+                        supported_parent = true;
+                } else if (streq(subsys, "amba")) {
+                        path_prepend(&path, "amba-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "amba-%s", sysname);
+                        parent = skip_subsystem(parent, "amba");
+                        supported_transport = true;
+                        supported_parent = true;
+                } else if (streq(subsys, "acpi")) {
+                        path_prepend(&path, "acpi-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "acpi-%s", sysname);
+                        parent = skip_subsystem(parent, "acpi");
+                        supported_parent = true;
+                } else if (streq(subsys, "xen")) {
+                        path_prepend(&path, "xen-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "xen-%s", sysname);
+                        parent = skip_subsystem(parent, "xen");
+                        supported_parent = true;
+                } else if (streq(subsys, "virtio")) {
+                        parent = skip_subsystem(parent, "virtio");
+                        supported_transport = true;
+                } else if (streq(subsys, "scm")) {
+                        path_prepend(&path, "scm-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "scm-%s", sysname);
+                        parent = skip_subsystem(parent, "scm");
+                        supported_transport = true;
+                        supported_parent = true;
+                } else if (streq(subsys, "ccw")) {
+                        path_prepend(&path, "ccw-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "ccw-%s", sysname);
+                        parent = skip_subsystem(parent, "ccw");
+                        supported_transport = true;
+                        supported_parent = true;
+                } else if (streq(subsys, "ccwgroup")) {
+                        path_prepend(&path, "ccwgroup-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "ccwgroup-%s", sysname);
+                        parent = skip_subsystem(parent, "ccwgroup");
+                        supported_transport = true;
+                        supported_parent = true;
+                } else if (streq(subsys, "ap")) {
+                        parent = handle_ap(parent, &path);
+                        supported_transport = true;
+                        supported_parent = true;
+                } else if (streq(subsys, "iucv")) {
+                        path_prepend(&path, "iucv-%s", sysname);
+                        if (compat_path)
+                                path_prepend(&compat_path, "iucv-%s", sysname);
+                        parent = skip_subsystem(parent, "iucv");
+                        supported_transport = true;
+                        supported_parent = true;
+                } else if (STR_IN_SET(subsys, "nvme", "nvme-subsystem")) {
+                        const char *nsid;
+
+                        if (sd_device_get_sysattr_value(dev, "nsid", &nsid) >= 0) {
+                                path_prepend(&path, "nvme-%s", nsid);
+                                if (compat_path)
+                                        path_prepend(&compat_path, "nvme-%s", nsid);
+
+                                if (streq(subsys, "nvme-subsystem")) {
+                                        r = find_real_nvme_parent(dev, &dev_other_branch);
+                                        if (r < 0)
+                                                return r;
+
+                                        parent = dev_other_branch;
+                                }
+
+                                parent = skip_subsystem(parent, "nvme");
+                                supported_parent = true;
+                                supported_transport = true;
+                        }
+                } else if (streq(subsys, "spi")) {
+                        const char *sysnum;
+
+                        if (sd_device_get_sysnum(parent, &sysnum) >= 0 && sysnum) {
+                                path_prepend(&path, "cs-%s", sysnum);
+                                parent = skip_subsystem(parent, "spi");
+                        }
+                }
+
+                if (!parent)
+                        break;
+                if (sd_device_get_parent(parent, &parent) < 0)
+                        break;
+        }
+
+        if (!path)
+                return -ENOENT;
+
+        /*
+         * Do not return devices with an unknown parent device type. They
+         * might produce conflicting IDs if the parent does not provide a
+         * unique and predictable name.
+         */
+        if (!supported_parent)
+                return -ENOENT;
+
+        /*
+         * Do not return block devices without a well-known transport. Some
+         * devices do not expose their buses and do not provide a unique
+         * and predictable name that way.
+         */
+        if (sd_device_get_subsystem(dev, &subsystem) >= 0 &&
+            streq(subsystem, "block") &&
+            !supported_transport)
+                return -ENOENT;
+
+        add_id_with_usb_revision(dev, test, path);
+
+        r = udev_builtin_add_property(dev, test, "ID_PATH", path);
+        if (r < 0)
+                log_device_debug_errno(dev, r, "Failed to add ID_PATH property, ignoring: %m");
+
+        add_id_tag(dev, test, path);
+
+        /*
+         * Compatible link generation for ATA devices
+         * we assign compat_link to the env variable
+         * ID_PATH_ATA_COMPAT
+         */
+        if (compat_path)
+                udev_builtin_add_property(dev, test, "ID_PATH_ATA_COMPAT", compat_path);
+
+        return 0;
+}
+
+const UdevBuiltin udev_builtin_path_id = {
+        .name = "path_id",
+        .cmd = builtin_path_id,
+        .help = "Compose persistent device path",
+        .run_once = true,
+};