From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=fR6Q=BJ=lists.ozlabs.org=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIM_INVALID,
	DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,
	SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham
	autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 74939C433DF
	for <linuxppc-dev@archiver.kernel.org>; Thu, 30 Jul 2020 05:43:25 +0000 (UTC)
Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by mail.kernel.org (Postfix) with ESMTPS id 265DF2084D
	for <linuxppc-dev@archiver.kernel.org>; Thu, 30 Jul 2020 05:43:25 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ehFzBJE0"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 265DF2084D
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3])
	by lists.ozlabs.org (Postfix) with ESMTP id 4BHK8C2trFzDqx6
	for <linuxppc-dev@archiver.kernel.org>; Thu, 30 Jul 2020 15:43:23 +1000 (AEST)
Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized)
 smtp.mailfrom=linuxfoundation.org (client-ip=198.145.29.99;
 helo=mail.kernel.org; envelope-from=gregkh@linuxfoundation.org;
 receiver=<UNKNOWN>)
Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none)
 header.from=linuxfoundation.org
Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key;
 unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256
 header.s=default header.b=ehFzBJE0; dkim-atps=neutral
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (No client certificate requested)
 by lists.ozlabs.org (Postfix) with ESMTPS id 4BHK1N5y8GzDqbf
 for <linuxppc-dev@lists.ozlabs.org>; Thu, 30 Jul 2020 15:37:28 +1000 (AEST)
Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl
 [83.86.89.107])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (No client certificate requested)
 by mail.kernel.org (Postfix) with ESMTPSA id 10E3F20838;
 Thu, 30 Jul 2020 05:37:25 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;
 s=default; t=1596087446;
 bh=QxvHKd0NyjuSLYu6cchEZo7GWM16xcMsonJiweZ+jDs=;
 h=Date:From:To:Cc:Subject:References:In-Reply-To:From;
 b=ehFzBJE096zIpEJXI1t7tggEmZg440Fg9mgKJWOoLAJMErEOCapDacGzuckH+Okkb
 Ae/nNLjNgNofvgmAVkB9FIhv9lL4Ymj3O+qM2VU+0qzbmXsppVvEgJHuZM3cqmsUbM
 v5movnmOqRlPPCSzv/0lt/HKH8Vibz+69sertXfM=
Date: Thu, 30 Jul 2020 07:37:16 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v2] powerpc/vio: drop bus_type from parent device
Message-ID: <20200730053716.GA3862178@kroah.com>
References: <20200406155748.6761-1-cascardo@canonical.com>
 <87ime56bax.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87ime56bax.fsf@mpe.ellerman.id.au>
X-BeenThere: linuxppc-dev@lists.ozlabs.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>
Cc: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>,
 Peter Rajnoha <prajnoha@redhat.com>, linuxppc-dev@lists.ozlabs.org
Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Sender: "Linuxppc-dev"
 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On Thu, Jul 30, 2020 at 11:28:38AM +1000, Michael Ellerman wrote:
> [ Added Peter & Greg to Cc ]
> 
> Thadeu Lima de Souza Cascardo <cascardo@canonical.com> writes:
> > Commit df44b479654f62b478c18ee4d8bc4e9f897a9844 ("kobject: return error
> > code if writing /sys/.../uevent fails") started returning failure when
> > writing to /sys/devices/vio/uevent.
> >
> > This causes an early udevadm trigger to fail. On some installer versions of
> > Ubuntu, this will cause init to exit, thus panicing the system very early
> > during boot.
> >
> > Removing the bus_type from the parent device will remove some of the extra
> > empty files from /sys/devices/vio/, but will keep the rest of the layout
> > for vio devices, keeping them under /sys/devices/vio/.
> 
> What exactly does it change?
> 
> I'm finding it hard to evaluate if this change is going to cause a
> regression somehow.
> 
> I'm also not clear on why removing the bus type is correct, apart from
> whether it fixes the bug you're seeing.
> 
> > It has been tested that uevents for vio devices don't change after this
> > fix, they still contain MODALIAS.
> >
> > Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
> > Fixes: df44b479654f ("kobject: return error code if writing /sys/.../uevent fails")
> 
> AFAICS there haven't been any other fixes for that commit. Do we know
> why it is only vio that was affected? (possibly because it's a fake bus
> to begin with?)

So there was an error previously, the core was ignoring it, and now it
isn't and to fix that you want to remove describing what bus a device is
on?

Huh???

> 
> cheers
> 
> > diff --git a/arch/powerpc/platforms/pseries/vio.c b/arch/powerpc/platforms/pseries/vio.c
> > index 37f1f25ba804..a94dab3972a0 100644
> > --- a/arch/powerpc/platforms/pseries/vio.c
> > +++ b/arch/powerpc/platforms/pseries/vio.c
> > @@ -36,7 +36,6 @@ static struct vio_dev vio_bus_device  = { /* fake "parent" device */
> >  	.name = "vio",
> >  	.type = "",
> >  	.dev.init_name = "vio",
> > -	.dev.bus = &vio_bus_type,
> >  };

Wait, a static 'struct device'?  You all are playing with fire there.
That's a reference counted object, and should never be declared like
that at all.

I see you register it, but never unregister it, why?  Why is it even
needed?

And if you remove the bus type of it, it will show up in a different
part of sysfs, so I think this patch will show a user-visable change,
right?

thanks,

greg k-h