linux-kernel - Re: [PATCH v3 3/5] mtd: nand: Add bb_per_lun and blocks_per_lun fields to nand

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Date:   Tue, 1 Nov 2016 13:32:32 -0500
From:   Zach Brown <zach.brown@...com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
CC:     <dwmw2@...radead.org>, <dedekind1@...il.com>, <richard@....at>,
        <linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        <computersforpeace@...il.com>
Subject: Re: [PATCH v3 3/5] mtd: nand: Add bb_per_lun and blocks_per_lun
 fields to nand_chip

On Tue, Nov 01, 2016 at 02:50:58PM +0100, Boris Brezillon wrote:
> On Fri, 28 Oct 2016 15:27:42 -0500
> Zach Brown <zach.brown@...com> wrote:
>
> > The fields bb_per_lun and blocks_per_lun are useful determining the
> > number of bad blocks a MTD needs to allocate. How they are set will
> > depend on if the chip is ONFI, JEDEC or a fuill-id entry in the nand_ids
> > table.
> >
> > Signed-off-by: Zach Brown <zach.brown@...com>
> > ---
> >  include/linux/mtd/nand.h | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> > index c5d3d502..efbe439 100644
> > --- a/include/linux/mtd/nand.h
> > +++ b/include/linux/mtd/nand.h
> > @@ -771,6 +771,9 @@ nand_get_sdr_timings(const struct nand_data_interface *conf)
> >   *			supported, 0 otherwise.
> >   * @jedec_params:	[INTERN] holds the JEDEC parameter page when JEDEC is
> >   *			supported, 0 otherwise.
> > + * @bb_per_lun:	[INTERN] the max number of bad blocks each LUN of a
> > + *			this nand device will encounter their life times.
> > + * @blocks_per_lun:	[INTERN] The number of PEBs in a LUN
> >   * @read_retries:	[INTERN] the number of read retry modes supported
> >   * @onfi_set_features:	[REPLACEABLE] set the features for ONFI nand
> >   * @onfi_get_features:	[REPLACEABLE] get the features for ONFI nand
> > @@ -853,6 +856,8 @@ struct nand_chip {
> >  		struct nand_onfi_params	onfi_params;
> >  		struct nand_jedec_params jedec_params;
> >  	};
> > +	__le16 bb_per_lun;
> > +	__le32 blocks_per_lun;
>
> Two things I don't like here:
> - you use little-endian types, while it should use native endianness.
>   Make it easier, and just declare those fields as int (or unsigned
>   int).
> - you stick to the ONFI spec, while I'd prefer to see the term lun
>   replaced by die, and I wonder if we don't already have a field
>   storing the number of blocks per die (I might be wrong though).
>

I looked for an existing field for number of blocks per die and could not find
it. Perhaps you were remembering chipsize? or numchips? I looked at how they
were calculated and chipsize is a multiple of (blocks_per_lun * lun_count) so
it can't be used to find blocks_per_lun without storing lun_count anyways.
Let me know if you think I missed something.