linux-kernel - Re: [PATCH v4 04/23] mtd: nand: denali: avoid hard-coding ECC step, strength, bytes

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Date:   Wed, 7 Jun 2017 16:21:15 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org,
        Richard Weinberger <richard@....at>,
        Marek Vasut <marek.vasut@...il.com>,
        Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mtd@...ts.infradead.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Chuanxiao Dong <chuanxiao.dong@...el.com>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Brian Norris <computersforpeace@...il.com>,
        Enrico Jorns <ejo@...gutronix.de>,
        David Woodhouse <dwmw2@...radead.org>,
        Graham Moore <grmoore@...nsource.altera.com>
Subject: Re: [PATCH v4 04/23] mtd: nand: denali: avoid hard-coding ECC step,
 strength, bytes

Hi Boris,


2017-06-07 16:02 GMT+09:00 Boris Brezillon <boris.brezillon@...e-electrons.com>:
> On Wed, 7 Jun 2017 12:09:31 +0900
> Masahiro Yamada <yamada.masahiro@...ionext.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.

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


> 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.

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

-- 
Best Regards
Masahiro Yamada