From: Boris Brezillon <boris.brezillon@collabora.com>
To: "Michał Kępień" <kernel@kempniu.pl>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
Boris Brezillon <bbrezillon@kernel.org>
Subject: Re: [PATCH] mtd: add MEMREAD ioctl
Date: Thu, 30 Sep 2021 08:51:33 +0200 [thread overview]
Message-ID: <20210930085133.13b5a228@collabora.com> (raw)
In-Reply-To: <YVTBoAnQKYLNpOPc@larwa.hq.kempniu.pl>
Hu Michal,
On Wed, 29 Sep 2021 21:42:24 +0200
Michał Kępień <kernel@kempniu.pl> wrote:
> Miquel, Boris,
>
> Thank you both for your input.
>
> > > I do agree that a new interface is needed, but if we're adding a new
> > > entry point, let's make sure it covers all possible use cases we have
> > > now. At the very least, I think we're missing info about the maximum
> > > number of corrected bits per ECC region on the portion being read.
> > > Propagating EUCLEAN errors is nice, but it's not precise enough IMHO.
> > >
> > > I remember discussing search a new READ ioctl with Sascha Hauer a few
> > > years back, but I can't find the discussion...
>
> I think this is the thread in question:
>
> https://www.infradead.org/pipermail/linux-mtd/2016-April/thread.html#67085
>
> In fact, it looks like Boris beat me to preparing a draft patch adding a
> MEMREAD ioctl by some five years:
>
> https://www.infradead.org/pipermail/linux-mtd/2016-April/067187.html
Exactly the one I was referring to. Note that this patch still contains
the unbounded malloc which I think is worth fixing, but other than
that and the addition of ECC stats, it looks pretty similar to yours.
>
> It is apparently true that "everything that can be invented has been
> invented"... :-) I did search the web for existing mentions of a
> MEMREAD ioctl before submitting my patch, but this thread did not turn
> up in the results :(
>
> Anyway, back in 2016, Sascha hinted that he might move forward with the
> draft prepared by Boris:
>
> https://www.infradead.org/pipermail/linux-mtd/2016-April/067215.html
>
> but I cannot find any related submissions from Sascha in linux-mtd's
> Patchwork.
>
> > We also discussed a mtd_io_op some time ago, which would equivalently
> > replace mtd_oob_ops at some point, including more information such as
> > the bitflips which happened on every chunk instead of the information
> > regarding the maximum number of bitflips in one of the chunks only.
>
> Is that discussion available online? Search engines seem to be
> oblivious to that term, which makes it hard for me to get acquainted
> with that idea and/or to comment on it ;)
Not sure this has been discussed publicly, but I remember suggesting
that to Miquel a while ago to simplify the in-kernel MTD interface.
>
> > IIRC the point was to get rid of the mtd_{read,write}{,_oob} hooks and
> > structures in favor of a more robust and complete set of operations.
>
> That sounds like a major overhaul, right?
>
> I guess the big question from my perspective is: should I revive Boris'
> original effort on the MEMREAD ioctl (which returns more detailed
> bitflip stats in the structure passed by user space) or would that be a
> waste of time because the subsystem will be switched over wholesale to a
> new way of doing I/O (mtd_io_op) in the foreseeable future and therefore
> exposing yet another ioctl to user space today would be frowned upon?
>
That's not my call to make, but I think those 2 things are orthogonal
and can be addressed separately.
Regards,
Boris
next prev parent reply other threads:[~2021-09-30 6:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 7:02 [PATCH] mtd: add MEMREAD ioctl Michał Kępień
2021-09-28 13:58 ` Miquel Raynal
2021-09-28 14:24 ` Boris Brezillon
2021-09-28 14:35 ` Miquel Raynal
2021-09-29 19:42 ` Michał Kępień
2021-09-30 6:51 ` Boris Brezillon [this message]
2021-09-30 8:47 ` Miquel Raynal
2021-09-30 13:54 ` Michał Kępień
2021-09-30 13:58 ` Miquel Raynal
2021-09-30 14:22 ` Boris Brezillon
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