Re: [PATCH] ACPI / device_sysfs: Use OF_MODALIAS for "compatible" modalias

[Kai-Heng Feng <kai.heng.feng@canonical.com>]

On Tue, Jan 19, 2021 at 4:27 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Tue, Jan 19, 2021 at 04:15:13PM +0800, Kai-Heng Feng wrote:
> > Commit 8765c5ba1949 ("ACPI / scan: Rework modalias creation when
> > "compatible" is present") may create two "MODALIAS=" in uevent file if
> > conditions are met.
> >
> > This breaks systemd-udevd, which assumes each "key" in uevent file is
> > unique. The internal implementation of systemd-udevd overwrites the
> > first MODALIAS with the second one, so its kmod rule doesn't load driver
> > for the first MODALIAS.
> >
> > Right now it doesn't seem to have any user relies on the second
> > MODALIAS, so change it to OF_MODALIAS to workaround the issue.
> >
> > Reference: https://github.com/systemd/systemd/pull/18163
> > Fixes: 8765c5ba1949 ("ACPI / scan: Rework modalias creation when "compatible" is present")
> > Cc: AceLan Kao <acelan.kao@canonical.com>
> > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
> > Cc: Mika Westerberg <mika.westerberg@linux.intel.com>,
> > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> > ---
> >  drivers/acpi/device_sysfs.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/device_sysfs.c b/drivers/acpi/device_sysfs.c
> > index 96869f1538b9..c92b671cb816 100644
> > --- a/drivers/acpi/device_sysfs.c
> > +++ b/drivers/acpi/device_sysfs.c
> > @@ -260,7 +260,7 @@ int __acpi_device_uevent_modalias(struct acpi_device *adev,
> >       if (!adev->data.of_compatible)
> >               return 0;
> >
> > -     if (len > 0 && add_uevent_var(env, "MODALIAS="))
> > +     if (len > 0 && add_uevent_var(env, "OF_MODALIAS="))
>
> Who will use OF_MODALIAS and where have you documented it?

After this lands in mainline, I'll modify the pull request for systemd
to add a new rule for OF_MODALIAS.
I'll modify the comment on the function to document the change.

Kai-Heng

>
> thanks,
>
> greg k-h