linux-kernel - Re: [PATCH] mtd: nand: gpmi: add proper raw access support

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Message-ID: <20140915144259.GA1947@localhost.localdomain>
Date:	Mon, 15 Sep 2014 22:43:02 +0800
From:	Huang Shijie <shijie8@...il.com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Huang Shijie <shijie.huang@...el.com>,
	Mike Voytovich <mvoytovich@...pal.com>,
	linux-kernel@...r.kernel.org, Huang Shijie <b32955@...escale.com>,
	linux-mtd@...ts.infradead.org, Roy Lee <roylee@...pal.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] mtd: nand: gpmi: add proper raw access support

On Sat, Sep 13, 2014 at 10:38:41AM -0700, Brian Norris wrote:
> On Sat, Sep 13, 2014 at 11:36:24PM +0800, Huang Shijie wrote:
> > On Fri, Sep 12, 2014 at 02:30:50PM +0200, Boris BREZILLON wrote:
> > > This test validates what's returned by ecc_strength file in sysfs
> > > (which in turn is specified by the NAND controller when initializing
> > > the NAND chip).
> > > 
> > > Doing this should not imply knowing the ECC algorithm in use in the
> > > NAND controller or the layout used to store data on NAND.
> > the difficulty is that the ECC parity area can be not byte aligned.
> 
> Is there a problem with just rounding up to the nearest byte alignment
> and ignoring the few bits that are wasted?

I feel a little confused with the two hooks.

does the ecc->write_page_raw need to write the ECC parity data?

The page's layout after an ecc->write_page  will look like this:
                                              (Block Mark)
                                                    |      |
                                                    |  D   |
                                                    |<---->|
                                                    V      V
     +---+----------+-+----------+-+----------+-+----------+-+
     | M |   data   |E|   data   |E|   data   |E|   data   |E|
     +---+----------+-+----------+-+----------+-+----------+-+

What will the page's layout look like after the ecc->write_page_raw?


thanks
Huang Shijie

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