Messages in this thread | | | Date | Thu, 30 Sep 2021 08:51:33 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH] mtd: add MEMREAD ioctl |
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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
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