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 <20171205112815.0b59ab2d@bbrezillon>
From: Masahiro Yamada <yamada.masahiro@socionext.com>
Date: Tue, 5 Dec 2017 19:41:45 +0900
Message-ID: <CAK7LNASHE1qKe5m24KvZWjp4GsCmop9h+PcQD--ecgQV6mm=cg@mail.gmail.com>
Subject: Re: [PATCH] mtd: nand: squash struct nand_buffers into struct nand_chip
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Kamal Dasu <kdasu.kdev@gmail.com>, Richard Weinberger <richard@nod.at>,
        Han Xu <han.xu@nxp.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Marek Vasut <marek.vasut@gmail.com>, Chen-Yu Tsai <wens@csie.org>,
        Broadcom Kernel Feedback List 
        <bcm-kernel-feedback-list@broadcom.com>,
        Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        Maxime Ripard <maxime.ripard@free-electrons.com>,
        Brian Norris <computersforpeace@gmail.com>,
        David Woodhouse <dwmw2@infradead.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
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2017-12-05 19:28 GMT+09:00 Boris Brezillon <boris.brezillon@free-electrons.com>:
> On Tue, 5 Dec 2017 19:02:26 +0900
> Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
>
>> Hi Boris,
>>
>> 2017-12-04 18:10 GMT+09:00 Boris Brezillon
>> <boris.brezillon@free-electrons.com>:
>>
>> >>       }
>> >>
>> >>       if (!(chip->options & NAND_OWN_BUFFERS)) {
>> >> -             nbuf = kzalloc(sizeof(*nbuf), GFP_KERNEL);
>> >> -             if (!nbuf)
>> >> +             chip->ecccalc = kmalloc(mtd->oobsize, GFP_KERNEL);
>> >> +             if (!chip->ecccalc)
>> >>                       return -ENOMEM;
>> >>
>> >> -             nbuf->ecccalc = kmalloc(mtd->oobsize, GFP_KERNEL);
>> >> -             if (!nbuf->ecccalc) {
>> >> +             chip->ecccode = kmalloc(mtd->oobsize, GFP_KERNEL);
>> >> +             if (!chip->ecccode) {
>> >>                       ret = -ENOMEM;
>> >>                       goto err_free_nbuf;
>> >>               }
>> >
>> > Hm, again not directly related to this patch, but I wonder if we
>> > couldn't allocate those buffers only when they are really needed.
>> > For example, most NAND controllers do the ECC calculation/correct
>> > in HW and simply don't need those buffers.
>>
>>
>> The only idea I came up with is to add a new flag,
>> but I am not sure if you are happy with it
>> because we are removing NAND_OWN_BUFFERS.
>
> All drivers using ->calc/code_buf are providing a ->correct() and/or
> ->calculate() method, so I thought we could make the allocation
> dependent on the presence of one of these hooks [1].
>
> The only exception is the denali driver, but I think we can patch it
> to not use the ->code_buf buffer [2].

Cool!


> [1]http://code.bulix.org/2ks7yp-236649
> [2]http://code.bulix.org/sxqx7o-236650
>

Thanks!

I can issue Acked-by for [2].


-- 
Best Regards
Masahiro Yamada