On Mon, Jan 18, 2021 at 04:12:38PM +0200, Mika Westerberg wrote:

Hi,

On Mon, Jan 18, 2021 at 02:50:33PM +0100, Rafael J. Wysocki wrote:

quoted

CC Mika and Andy.

On Mon, Jan 18, 2021 at 8:27 AM Kai-Heng Feng
[off-list ref] wrote:

quoted

On Sat, Jan 9, 2021 at 12:25 AM Kai-Heng Feng
[off-list ref] wrote:

quoted

Commit 8765c5ba19490 ("ACPI / scan: Rework modalias creation when
"compatible" is present") creates two modaliases for certain ACPI
devices. However userspace (systemd-udevd in this case) assumes uevent
file doesn't have duplicated keys, so two "MODALIAS=" breaks the
assumption.

Based on the assumption, systemd-udevd internally uses hashmap to
store each line of uevent file, so the second modalias always replaces
the first modalias.

My attempt [1] is to add a new key, "MODALIAS1" for the second
modalias. This brings up the question of whether each key in uevent
file is unique. If it's no unique, this may break may userspace.

Does anyone know if there's any user of the second modalias?
If there's no user of the second one, can we change it to OF_MODALIAS
or COMPAT_MODALIAS?

The only users I'm aware are udev and the busybox equivalent (udev,
mdev) but I'm not sure if they use the second second modalias at all so
OF_MODALIAS for the DT compatible string sounds like a good way to solve
this.

As udev seems to "break" with this (which is where we got the original
report from), I don't think you need to worry about that user :)

Does anyone use mdev anymore, and in any ACPI-supported systems?

thanks,

greg k-h