Re: Multiple MODALIAS= in uevent file confuses userspace
From: Andy Shevchenko
Date: Mon Jan 18 2021 - 09:53:02 EST
On Mon, Jan 18, 2021 at 04:12:38PM +0200, Mika Westerberg wrote:
> On Mon, Jan 18, 2021 at 02:50:33PM +0100, Rafael J. Wysocki wrote:
> > On Mon, Jan 18, 2021 at 8:27 AM Kai-Heng Feng
> > <kai.heng.feng@xxxxxxxxxxxxx> wrote:
> > > On Sat, Jan 9, 2021 at 12:25 AM Kai-Heng Feng
> > > <kai.heng.feng@xxxxxxxxxxxxx> wrote:
> > > >
> > > > 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  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
I agree with Mika here.
With Best Regards,