linux-kernel - Re: [PATCH] mtd: parser: cmdline: Support MTD names containing one or more colons

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Date:   Fri, 27 Nov 2020 08:32:02 -0800
From:   ron minnich <rminnich@...il.com>
To:     Sven Eckelmann <sven@...fation.org>
Cc:     linux-mtd@...ts.infradead.org, John Audia <graysky@...hlinux.us>,
        Adrian Schmutzler <freifunk@...ianschmutzler.de>,
        jstefek@...to.com,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Ron Minnich <rminnich@...gle.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH] mtd: parser: cmdline: Support MTD names containing one or
 more colons

I'm a bit worried about how tricky this starts to get. I'm inclined to
go back to an earlier implementation which used a character that had
not yet been used (iirc I used [] around the PCI ID in a very early
version). What if we used, e.g, a single ! and searched for that? It
need not be !; pick a character. Just something not already in use, as
the ambiguity around which ':' delimits the device has become an
issue, as you show.

Almost nothing in the original patch would change, save the character
being searched for. By using a character we'd never used, we'd avoid
breaking existing usage.

Comments?

On Sat, Nov 21, 2020 at 4:14 PM Sven Eckelmann <sven@...fation.org> wrote:
>
> On Wednesday, 29 April 2020 18:53:47 CET Ronald G. Minnich wrote:
> > From: Boris Brezillon <boris.brezillon@...labora.com>
> >
> > Looks like some drivers define MTD names with a colon in it, thus
> > making mtdpart= parsing impossible. Let's fix the parser to gracefully
> > handle that case: the last ':' in a partition definition sequence is
> > considered instead of the first one.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@...labora.com>
> > Signed-off-by: Ron Minnich <rminnich@...gle.com>
> > Tested-by: Ron Minnich <rminnich@...gle.com>
> > ---
> >  drivers/mtd/parsers/cmdlinepart.c | 23 ++++++++++++++++++++---
> >  1 file changed, 20 insertions(+), 3 deletions(-)
>
> This change broke OpenWrt booting on some IPQ40xx devices. Here for example
> the parts of the cmdline which the u-boot on an OpenMesh A62 sets
> automatically:
>
>     root=31:11 mtdparts=spi0.0:256k(0:SBL1),128k(0:MIBIB),384k(0:QSEE),64k(0:CDT),64k(0:DDRPARAMS),64k(0:APPSBLENV),512k(0:APPSBL),64k(0:ART),64k(custom),64k(0:KEYS),0x002b0000(kernel),0x00c80000(rootfs),15552k(inactive) rootfsname=rootfs rootwait
>
> This is then parsed by newpart as: KEYS),0x002b0000(kernel),0x00c80000(rootfs),15552k(inactive)
>
> And of course, this results in:
>
>     mtd: partition has size 0
>     [...]
>     /dev/root: Can't open blockdev
>     VFS: Cannot open root device "31:11" or unknown-block(31,11): error -6
>     Please append a correct "root=" boot option; here are the available partitions:
>     1f00           32768 mtdblock0
>     (driver?)
>     Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(31,11)
>     CPU1: stopping
>     CPU: 1 PID: 0 Comm:
>
> This affects OpenWrt since the commit d6a9a92e3217 ("kernel: bump 5.4 to
> 5.4.69") because this change was backported to Linux v5.4.69. Reverting
> this change fixes the problem for me.
>
> And if I see it correctly, this is also affecting the kernel (4.14) for
> the OpenWrt 18.06.x + 19.07.x branch because it can also be found in
> there as part of the v4.14.200 release.
>
> Another workaround is to replace the first "(" with a NULL too. See the
> attached patch for the one which I used to fix the OpenWrt bootup.
>
> Kind regards,
>         Sven