[PATCH] powerpc/pseries: remove returning ENODEV when uevent is triggered

[Lidong Zhong]

Hi Michael,

Thanks for your reply.

On Tue, Apr 9, 2024 at 4:46 PM Michael Ellerman <mpe at ellerman.id.au> wrote:

> Hi Lidong,
>
> Thanks for the patch.
>
> I'm not an expert on udev etc. so apologies if any of these questions
> are stupid.
>
> Lidong Zhong <lidong.zhong at suse.com> writes:
> > We have noticed the following nuisance messages during boot
> >
> > [    7.120610][ T1060] vio vio: uevent: failed to send synthetic uevent
> > [    7.122281][ T1060] vio 4000: uevent: failed to send synthetic uevent
> > [    7.122304][ T1060] vio 4001: uevent: failed to send synthetic uevent
> > [    7.122324][ T1060] vio 4002: uevent: failed to send synthetic uevent
> > [    7.122345][ T1060] vio 4004: uevent: failed to send synthetic uevent
> >
> > It's caused by either vio_register_device_node() failed to set
> dev->of_node or
> > the missing "compatible" property. Try return as much information as
> possible
> > instead of a failure.
>
> Does udev etc. cope with that? Can we just change the content of the
> MODALIAS value like that?
>
> With this patch we'll start emitting uevents for devices we previously
> didn't. I guess that's OK because nothing is expecting them?
>
> Can you include a log of udev showing the event firing and that nothing
> breaks.
>
> On my system here I see nothing matches the devices except for libvpd,
> which seems to match lots of things.
>

It's an issue reported by our customer. I am sorry I can't provide more
information because I  don't have the environment
to reproduce this issue. The only related log I got is shown below:

Feb 07 14:08:03 rb3i0060 udevadm[623]: vio: Failed to write 'add' to
'/sys/devices/vio/uevent', ignoring: No such device

Feb 07 14:08:03 rb3i0060 kernel: synth uevent: /devices/vio: failed to send
uevent

Feb 07 14:08:03 rb3i0060 kernel: vio vio: uevent: failed to send synthetic
uevent

Feb 07 14:08:03 rb3i0060 kernel: synth uevent: /devices/vio/4000: failed to
send uevent

Feb 07 14:08:03 rb3i0060 kernel: vio 4000: uevent: failed to send synthetic
uevent

Feb 07 14:08:03 rb3i0060 kernel: synth uevent: /devices/vio/4001: failed to
send uevent

Feb 07 14:08:03 rb3i0060 kernel: vio 4001: uevent: failed to send synthetic
uevent

Feb 07 14:08:03 rb3i0060 kernel: synth uevent: /devices/vio/4002: failed to
send uevent

Feb 07 14:08:03 rb3i0060 kernel: vio 4002: uevent: failed to send synthetic
uevent

Feb 07 14:08:03 rb3i0060 kernel: synth uevent: /devices/vio/4004: failed to
send uevent

Feb 07 14:08:03 rb3i0060 kernel: vio 4004: uevent: failed to send synthetic
uevent

Feb 07 14:08:03 rb3i0060 udevadm[623]: 4000: Failed to write 'add' to
'/sys/devices/vio/4000/uevent', ignoring: No such device

Feb 07 14:08:03 rb3i0060 udevadm[623]: 4001: Failed to write 'add' to
'/sys/devices/vio/4001/uevent', ignoring: No such device

Feb 07 14:08:03 rb3i0060 udevadm[623]: 4002: Failed to write 'add' to
'/sys/devices/vio/4002/uevent', ignoring: No such device

Feb 07 14:08:03 rb3i0060 udevadm[623]: 4004: Failed to write 'add' to
'/sys/devices/vio/4004/uevent', ignoring: No such device

systemd-udev-trigger service calls 'udevadm trigger --type=devices
--action=add' and kernel returns -ENODEV because either
dev->of_node is NULL or 'compatible' property is not present.  Similar
cases were already reported after some search, for example
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1827162
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1845319
I don't think it causes real problems but confusion to users.


> > diff --git a/arch/powerpc/platforms/pseries/vio.c
> b/arch/powerpc/platforms/pseries/vio.c
> > index 90ff85c879bf..62961715ca24 100644
> > --- a/arch/powerpc/platforms/pseries/vio.c
> > +++ b/arch/powerpc/platforms/pseries/vio.c
> > @@ -1593,12 +1593,13 @@ static int vio_hotplug(const struct device *dev,
> struct kobj_uevent_env *env)
> >
> >       dn = dev->of_node;
> >       if (!dn)
> > -             return -ENODEV;
> > +             goto out;
> >       cp = of_get_property(dn, "compatible", NULL);
> >       if (!cp)
> > -             return -ENODEV;
> > -
> > -     add_uevent_var(env, "MODALIAS=vio:T%sS%s", vio_dev->type, cp);
> > +             add_uevent_var(env, "MODALIAS=vio:T%s", vio_dev->type);
>
> If it's OK to skip the compatible property then we don't need the
> of_node at all, and we could always emit this, even when of_node is not
> available.
>

You mean something like this?
@@ -1592,13 +1592,10 @@ static int vio_hotplug(const struct device *dev,
struct kobj_uevent_env *env)
        const char *cp;

        dn = dev->of_node;
-       if (!dn)
-               return -ENODEV;
-       cp = of_get_property(dn, "compatible", NULL);
-       if (!cp)
-               return -ENODEV;
-
-       add_uevent_var(env, "MODALIAS=vio:T%sS%s", vio_dev->type, cp);
+       if (dn && (cp = of_get_property(dn, "compatible", NULL))
+               add_uevent_var(env, "MODALIAS=vio:T%sS%s", vio_dev->type,
cp);
+       else
+               add_uevent_var(env, "MODALIAS=vio:T%s", vio_dev->type);
        return 0;


>
> > +    else
> > +             add_uevent_var(env, "MODALIAS=vio:T%sS%s", vio_dev->type,
> cp);
> > +out:
> >       return 0;
> >  }
>
> I think we also should update the vio modalias_show() to follow the same
> logic, otherwise the uevent MODALIAS value and the modalias file won't
> match which is confusing.
>
> Preferably vio_hotplug() and modalias_show() would just call a common
> helper.
>
> cheers
>

Thanks for the suggestion. I'll send a v2 patch.


-- 
Regards,
Lidong Zhong
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