From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Mon, 6 Dec 2021 07:05:35 +0000 (+0900)
Subject: udev/path-id: comment why USB host number is dropped from the PATH_ID
X-Git-Tag: v250-rc1~64^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6885a857e4071536d3e378f0bf41c02e959a7681;p=thirdparty%2Fsystemd.git

udev/path-id: comment why USB host number is dropped from the PATH_ID

Closes #21617.

The comment is borrowed from https://github.com/systemd/systemd/pull/21620#discussion_r762521508.
---

diff --git a/src/udev/udev-builtin-path_id.c b/src/udev/udev-builtin-path_id.c
index 9f71fadeea8..6fdd3eceea3 100644
--- a/src/udev/udev-builtin-path_id.c
+++ b/src/udev/udev-builtin-path_id.c
@@ -503,6 +503,10 @@ static sd_device *handle_usb(sd_device *parent, char **path) {
                 return parent;
         port++;
 
+        /* 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. */
+
         path_prepend(path, "usb-0:%s", port);
         return skip_subsystem(parent, "usb");
 }