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

[Peter Pan]

Hi Boris,

On Wed, Jan 6, 2016 at 10:29 PM, Boris Brezillon
<boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 30 Dec 2015 09:31:06 +0100
> Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
>
>> Hi Peter,
>>
>> On Wed, 30 Dec 2015 15:18:39 +0800
>> ææ <peterpansjtu@xxxxxxxxx> wrote:
>>
>> > Hi Boris and Ezequiel,
>> >
>> > 2015-12-29 23:11 GMT+08:00 Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>:
>> > > On Tue, 29 Dec 2015 12:07:50 -0300
>> > > Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx> wrote:
>> > >
>> > >> On 29 December 2015 at 06:35, Boris Brezillon
>> > >> <boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
>> > >> > Hi,
>> > >> >
>> > >> > On Mon, 28 Dec 2015 17:42:50 -0300
>> > >> > Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx> wrote:
>> > >> >
>> > >> >> This is looking a lot better, thanks for the good work!
>> > >> >>
>> > >> >> On 15 December 2015 at 02:59, Peter Pan <peterpansjtu@xxxxxxxxx> 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
>> > >> >> >         âââ Kconfig
>> > >> >> >         âââ Makefile
>> > >> >> >         âââ ...
>> > >> >> >         âââ 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?
>>
>> Absolutely, that was the idea: move everything into the
>> drivers/mtd/nand directory (with the structure described above), keep
>> some specific logic for each interface type, and see if we can factor
>> out some common code (I noticed that SPI NAND devices have a parameter
>> page which looks similar to the one exposed by ONFI compliant devices,
>> except this parameter page is retrieved using a different command, the
>> same goes for the ->{set,get}_features() functions).
>> But let's focus on the nand_bbt code for now.
>>
>> >
>> > Also, please review the BBT patch if you have time. I think it's
>> > helpful on the new NAND code
>> > hierarchy.
>>
>> I'll try to review it this week.
>
> I'm a bit late, but I think I've reviewed most of it now.

I already go through your comments. They are very precious and
instructive. Thank you
a lot for taking time to do the review. I'll remake the patches and
send the v3 out soon.

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

Thanks,
Peter Pan
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