linux-kernel - Re: [PATCH] Make JFFS2 endianness configurable

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Message-ID: <20181102003434.GW32577@ZenIV.linux.org.uk>
Date:   Fri, 2 Nov 2018 00:34:34 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Daniel Walker <danielwa@...co.com>
Cc:     Nikunj Kela <nkela@...co.com>,
        David Woodhouse <dwmw2@...radead.org>,
        xe-linux-external@...co.com, Rod Whitby <rod@...tby.id.au>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make JFFS2 endianness configurable

On Thu, Nov 01, 2018 at 05:02:36PM -0700, Daniel Walker wrote:
> 
> 
> 
> On Thu, Nov 01, 2018 at 03:56:03PM -0700, Nikunj Kela wrote:
> > This patch allows the endianness of the JFSS2 filesystem to be
> > specified by config options.
> > 
> > It defaults to native-endian (the previously hard-coded option).
> > 
> > Some architectures benefit from having a single known endianness
> > of JFFS2 filesystem (for data, not executables) independent of the
> > endianness of the processor (ARM processors can be switched to either
> > endianness at run-time).
> > 
> 
> 
> The description is pretty sad .. We have a product which we released that uses
> JFFS2, and that product was release with a kernel in one endianness. Then later
> on we decided to change the endianness and now we're stuck with a JFFS2
> partition that has the wrong endiannes, in a released product. This patch allows
> us to set the endianness to something different from the architecture setting.
> 
> So there a significant use case for the change, at least for Cisco.

FWIW, can't we detect it at mount time, as e.g. UFS does?