From 1c7dfbf249f5320d0675fcb03556a55881e21457 Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Fri, 3 Aug 2012 10:52:24 +0200 Subject: [PATCH] udev: path_id - add comment about the unrteliable rebase logic --- src/udev/udev-builtin-path_id.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/src/udev/udev-builtin-path_id.c b/src/udev/udev-builtin-path_id.c index 8eac991d3..720f616da 100644 --- a/src/udev/udev-builtin-path_id.c +++ b/src/udev/udev-builtin-path_id.c @@ -236,7 +236,23 @@ static struct udev_device *handle_scsi_default(struct udev_device *parent, char if (sscanf(name, "%d:%d:%d:%d", &host, &bus, &target, &lun) != 4) return NULL; - /* rebase host offset to get the local relative number */ + /* + * 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. + */ basenum = -1; base = strdup(udev_device_get_syspath(hostdev)); if (base == NULL) -- 2.30.2