linux-kernel - Re: [PATCH 1/3] mtd: nand: Add on-die ECC support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150428032213.GI19571@brian-ubuntu>
Date:	Mon, 27 Apr 2015 20:22:13 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	punnaiah choudary kalluri <punnaia@...inx.com>
Cc:	Richard Weinberger <richard@....at>,
	Ben Shelton <ben.shelton@...com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Punnaiah Choudary Kalluri 
	<punnaiah.choudary.kalluri@...inx.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>
Subject: Re: [PATCH 1/3] mtd: nand: Add on-die ECC support

On Tue, Apr 28, 2015 at 08:18:12AM +0530, punnaiah choudary kalluri wrote:
> On Tue, Apr 28, 2015 at 4:53 AM, Brian Norris
> <computersforpeace@...il.com> wrote:
> > On Tue, Apr 28, 2015 at 12:19:16AM +0200, Richard Weinberger wrote:
> >> Oh, I thought every driver has to implement that function. ;-\
> >
> > Nope.
> >
> >> But you're right there is a corner case.
> >
> > And it's not the only one! Right now, there's no guarantee even that
> > read_buf() returns raw data, unmodified by the SoC's controller. Plenty
> > of drivers actually have HW-enabled ECC turned on by default, and so
> > they override the chip->ecc.read_page() (and sometimes
> > chip->ecc.read_page_raw() functions, if we're lucky) with something
> > that pokes the appropriate hardware instead. I expect anything
> > comprehensive here is probably going to have to utilize
> > chip->ecc.read_page_raw(), at least if it's provided by the hardware
> > driver.
> 
> Yes, overriding the chip->ecc.read_page_raw would solve this.

I'm actually suggesting that (in this patch set, for on-die ECC
support), maybe we *shouldn't* override chip->ecc.read_page_raw() and
leave that to be defined by the driver, and then on-die ECC support
should be added in a way that just calls chip->ecc.read_page_raw(). This
should work for any driver that already properly supports the raw
callbacks.

> Agree that
> read_buf need not be returning raw data always including my new driver for
> arasan nand flash controller.

I agree with that. At the moment, chip->read_buf() really has very
driver-specific meaning. Not sure if that's really a good thing, but
it's the way things are...

> http://lkml.iu.edu/hypermail/linux/kernel/1504.2/00313.html

In the half a minute I just spent looking at this (I may review it
properly later), I noted a few things:

1. you don't implement ecc.read_page_raw(); this means we'll probably
have trouble supporting on-die ECC with your driver, among other things

2. your patch is all white-space mangled. Please use your favorite
search engine to figure out how to get that right. git-send-email is
your friend.

Thanks,
Brian
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/