linux-kernel - Re: [PATCH v2 00/12] mtd: nand_bbt: introduce independent nand BBT

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Date:	Wed, 30 Dec 2015 15:18:39 +0800
From:	潘栋 <peterpansjtu@...il.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
	Brian Norris <computersforpeace@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Frans Klaver <fransklaver@...il.com>,
	Peter Pan <peterpandong@...ron.com>, beanhuo@...ron.com,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	karlzhang@...ron.com
Subject: Re: [PATCH v2 00/12] mtd: nand_bbt: introduce independent nand BBT

Hi Boris and Ezequiel,

2015-12-29 23:11 GMT+08:00 Boris Brezillon <boris.brezillon@...e-electrons.com>:
> On Tue, 29 Dec 2015 12:07:50 -0300
> Ezequiel Garcia <ezequiel@...guardiasur.com.ar> wrote:
>
>> On 29 December 2015 at 06:35, Boris Brezillon
>> <boris.brezillon@...e-electrons.com> wrote:
>> > Hi,
>> >
>> > On Mon, 28 Dec 2015 17:42:50 -0300
>> > Ezequiel Garcia <ezequiel@...guardiasur.com.ar> wrote:
>> >
>> >> This is looking a lot better, thanks for the good work!
>> >>
>> >> On 15 December 2015 at 02:59, Peter Pan <peterpansjtu@...il.com> wrote:
>> >> > Currently nand_bbt.c is tied with struct nand_chip, and it makes other
>> >> > NAND family chips hard to use nand_bbt.c. Maybe it's the reason why
>> >> > onenand has own bbt(onenand_bbt.c).
>> >> >
>> >> > Separate struct nand_chip from BBT code can make current BBT shareable.
>> >> > We create struct nand_bbt to take place of nand_chip in nand_bbt.c.
>> >> > Struct nand_bbt contains all the information BBT needed from outside and
>> >> > it should be embedded into NAND family chip struct (such as struct nand_chip).
>> >> > NAND family driver should allocate, initialize and free struct nand_bbt.
>> >> >
>> >> > Below is mtd folder structure we want:
>> >> >         mtd
>> >> >         ├── Kconfig
>> >> >         ├── Makefile
>> >> >         ├── ...
>> >> >         ├── nand_bbt.c
>> >>
>> >> Hm.. I'm not sure about having nand_bbt.c in drivers/mtd.
>> >> What's wrong with drivers/mtd/nand ?
>> >
>> > I haven't reviewed the series yet, but I agree. If the BBT code is only
>> > meant to be used on NAND based devices, it should probably stay in
>> > drivers/mtd/nand.
>> >
>> >>
>> >> In fact, I  was thinking we could go further and clean up the directories a bit
>> >> by separating core code, from controllers code, from SPI NAND code:
>> >>
>> >> drivers/mtd/nand/
>> >> drivers/mtd/nand/controllers
>> >> drivers/mtd/nand/spi
>> >>
>> >> Makes any sense?
>> >
>> > Actually I had the secret plan of moving all (raw) NAND controller
>> > drivers into the drivers/mtd/nand/controllers directory, though this
>> > was for a different reason: I'd like to create another directory for
>> > manufacturer specific code in order to support some advanced features
>> > on NANDs that do not implement (or only partially implement) the ONFI
>> > standard.
>> >
>> > The separation you're talking about here is more related to the
>> > interface used to communicate with the NAND chip.
>> >
>> > How about using the following hierarchy?
>> >
>> > drivers/mtd/nand/<nand-core-code>
>> > drivers/mtd/nand/interfaces/raw/<raw-nand-core-code>
>> > drivers/mtd/nand/interfaces/raw/controllers/<raw-nand-controller-drivers>
>> > drivers/mtd/nand/interfaces/spi/<spi-nand-code>
>> > drivers/mtd/nand/interfaces/onenand/<onenand-code>
>> > drivers/mtd/nand/chips/<manufacturer-spcific-code>
>> >
>> > What do you think?
>> >
>>
>> I believe we are bikeshedding here, but what the heck.
>>
>> That seems too involved. A simpler hierarchy could be clear enough,
>> and seems to follow what other subsystems do:
>>
>> drivers/mtd/nand/<all-nand-core-code>
>> drivers/mtd/nand/raw/<raw-nand-controller-drivers>
>
> And probably some common logic in there too.
>
>> drivers/mtd/nand/spi/<spi-nand-code>
>> drivers/mtd/nand/onenand/<onenand-code>
>> drivers/mtd/nand/chips/<manufacturer-spcific-code>
>>
>
> I'm fine with this one too ;-).

I'm fine with this structure too. drivers/mtd/nand folder becomes top folder for
all NAND based devices. Because (raw)NAND, SPI-NAND and ONENAND have
different command set and feature, each has its own core - nand_base.c
spi-nand-base.c
and onenand_base.c. So maybe it'll take a lot effort to abstract a
all-nand-core-code
(of course BBT should be one of them). What's your opinion?

Also, please review the BBT patch if you have time. I think it's
helpful on the new NAND code
hierarchy.

>
> --
> Boris Brezillon, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com

Thanks
Peter Pan
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