linux-kernel - Re: [PATCH 17/39] mtd: nand: denali: support HW_ECC

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Date:   Wed, 30 Nov 2016 08:51:01 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mtd@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>
Subject: Re: [PATCH 17/39] mtd: nand: denali: support HW_ECC_FIXUP
 capability

On Wed, 30 Nov 2016 15:20:10 +0900
Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:

> Hi Boris,
> 
> 
> 2016-11-28 1:09 GMT+09:00 Boris Brezillon <boris.brezillon@...e-electrons.com>:
>                                         &max_bitflips);
> >
> > Okay, so you currently have two ways of handling ECC errors. What if a
> > new revision introduces yet another way to do it?
> >
> > How about making denali_caps a structure where you have one (or several)
> > function pointers to implement operations differently depending on the
> > IP revision?
> >
> > struct denali_caps {
> >         u32 feature_flags; /* If needed. */
> >         bool (*handle_ecc)(...);
> >         ...
> > };
> >  
> 
> I think a problem is the difference of function arguments:
> 
> static bool denali_hw_ecc_fixup(struct denali_nand_info *denali,
>                                 unsigned int *max_bitflips)
> 
>      vs
> 
> static bool denali_sw_ecc_fixup(struct denali_nand_info *denali, u8 *buf,
>                                 u32 irq_status, unsigned int *max_bitflips)
> 
> 
> I do not want to pass redundant arguments,
> which are used for one, but not used for the other.
> 

We do that all the time when defining generic interfaces.

> 
> We do not need to think about the situation that may not happen.
> If happens, we can refactor the code any time.
> 

Well, as I said in my other reply, I still think it's better to plan
for this now, rather than having to change a lot things when we appear
to need this. But that's only my POV, and I don't care enough to fight.