linux-kernel - Re: [PATCH v1 4/5] mtd: rawnand: meson: clear OOB buffer before read

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Date:   Wed, 3 May 2023 21:48:38 +0200
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Arseniy Krasnov <avkrasnov@...rdevices.ru>,
        Liang Yang <liang.yang@...ogic.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Yixun Lan <yixun.lan@...ogic.com>, oxffffaa@...il.com,
        kernel@...rdevices.ru, linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        "yonghui.yu" <yonghui.yu@...ogic.com>
Subject: Re: [PATCH v1 4/5] mtd: rawnand: meson: clear OOB buffer before read

Sorry for joining the party late.

On Wed, May 3, 2023 at 10:07 AM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > So for me main question here is:
> >
> > How JFFS2 should work with controllers where we can't update data and OOB
> > independently? Driver of this filesystem knows nothing about this features of
> > the controller.
> >
> > Or JFFS2 works incorrectly in my case when it tries to call write page callback
> > after calling write OOB callback (IIUC it is better to ask Richard as You mentioned above).
> >
> > Or may be it is better to suppress OOB write callback (or set it to NULL) in this
> > driver as in vendor's driver?
>
> I would assume using the unprotected free OOB bytes to store the
> cleanmarkers should work. But that's a bit fragile and very filesystem
> oriented. I don't like this much. But on the other side JFFS2 is
> legacy, you should use UBI (which does not play with OOB areas) :-)

Please note that JFFS2's main use case is NOR flash. Support for NAND
flash was never
considered as fully complete/stable. That's why UBIFS (JFFS3 in the
very beginning)
was invented.

Thanks,
//richard