linux-kernel - Re: [PATCH v4 2/5] drivers/of: do not add memory for unavailable nodes

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Message-Id: <20161023015107.527l4fvnh2nrup5u@arbab-vm>
Date:   Sat, 22 Oct 2016 20:51:08 -0500
From:   Reza Arbab <arbab@...ux.vnet.ibm.com>
To:     Alistair Popple <apopple@....ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stewart Smith <stewart@...ux.vnet.ibm.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tang Chen <tangchen@...fujitsu.com>, linux-mm@...ck.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Bharata B Rao <bharata@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>
Subject: Re: [PATCH v4 2/5] drivers/of: do not add memory for unavailable
 nodes

Hi Alistair,

On Fri, Oct 21, 2016 at 05:22:54PM +1100, Alistair Popple wrote:
>>From what I can tell it seems that kernels without this patch will try 
>and use this memory even if it is marked in the device-tree as 
>status="disabled" which could lead to problems for older kernels when 
>we start exporting this property from firmware.
>
>Arguably this might not be such a problem in practice as we probably 
>don't have many (if any) existing kernels that will boot on hardware 
>exporting these properties.

Yes, I think you've got it right.

>However given this patch seems fairly independent perhaps it is worth 
>sending as a separate fix if it is not going to make it into this 
>release?

Michael,

If this set as a whole is going to miss the release, would it be helpful 
for me to resend 1/5 and 2/5 as a separate set? They are the minimum 
needed to prevent the possible forward compatibility issue Alistair 
describes.

-- 
Reza Arbab