linux-kernel - Re: [PATCH] mtd: nand: squash struct nand_buffers into struct nand

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Message-ID: <CAK7LNATtk9=i3HkPrW=F1YtnM1vvEM3NtMZcPNi_0C5s_X1X1A@mail.gmail.com>
Date:   Tue, 5 Dec 2017 19:02:26 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Kamal Dasu <kdasu.kdev@...il.com>,
        Richard Weinberger <richard@....at>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Broadcom Kernel Feedback List 
        <bcm-kernel-feedback-list@...adcom.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Han Xu <han.xu@....com>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mtd: nand: squash struct nand_buffers into struct nand_chip

Hi Boris,

2017-12-04 18:10 GMT+09:00 Boris Brezillon <boris.brezillon@...e-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.





-- 
Best Regards
Masahiro Yamada