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SubjectRe: [PATCH v4 04/23] mtd: nand: denali: avoid hard-coding ECC step, strength, bytes
On Wed, 7 Jun 2017 16:21:15 +0900
Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> Hi Boris,
>
>
> 2017-06-07 16:02 GMT+09:00 Boris Brezillon <boris.brezillon@free-electrons.com>:
> > On Wed, 7 Jun 2017 12:09:31 +0900
> > Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
> >
> >> >> +
> >> >> +static int denali_ecc_setup(struct mtd_info *mtd, struct nand_chip *chip,
> >> >> + struct denali_nand_info *denali)
> >> >> +{
> >> >> + struct nand_ecc_caps caps;
> >> >> + int ret;
> >> >> +
> >> >> + caps.stepinfos = denali->stepinfo;
> >> >> + caps.nstepinfos = 1;
> >> >> + caps.calc_ecc_bytes = denali_calc_ecc_bytes;
> >> >> + caps.oob_reserve_bytes = denali->bbtskipbytes;
> >> >
> >> > If you get rid of this oob_reserve_bytes field, you can define caps as
> >> > a static const and even directly store ecc_caps in denali_nand_info.
> >>
> >> To make caps static const, denali_calc_ecc_bytes must be exported
> >> to be referenced from denali_dt/denali_pci.
> >> I am reluctant to do it.
> >
> > You already duplicate other information in denali_dt.c and
> > denali_pci.c,
>
> The ECC step-size and strength are tightly associated to each IP variant.
> I see duplication between denali_dt and denali_pci, but it is just because
> Intel and Altera happened to have the same parameters.

It's still duplication.

>
> On the other hand, denali_calc_ecc_bytes() is common to all variants
> because ECC algorithm is not customizable.

Yes, I agree.

>
>
> > so what prevents you from duplicating this one-line
> > function?
> >
> > Also, denali core already exports 2 functions,
>
> They are entries for probe/remove.
>
> > I don't see the problem
> > in exporting the common nand_ecc_caps object. Why are you reluctant to
> > that?
>
> denali_calc_ecc_bytes() is independent of DT, PCI, or whatever.
> I see less reason to expose it.

I don't get that one. The fact that it's a generic implementation makes
it a good match for something you want to have in the core and expose
to DT/PCI implems.

>
> caps is only used on probing, so I used a local variable.
> I do not think it is a big problem.
>

It is to me, because you'll be the only user of the API at first, and
people tend to copy&paste code from other drivers.
nand_ecc_caps is really something that should be const and attached to
a specific IP revision.

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