linux-kernel - Re: [PATCH v3 00/27] kill devm_ioremap

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Message-ID: <c28ac0bc-8bd2-3dce-3167-8c0f80ec601e@c-s.fr>
Date:   Sun, 24 Dec 2017 09:55:18 +0100
From:   christophe leroy <christophe.leroy@....fr>
To:     Guenter Roeck <linux@...ck-us.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        Yisheng Xie <xieyisheng1@...wei.com>
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Subject: Re: [PATCH v3 00/27] kill devm_ioremap_nocache



Le 23/12/2017 à 16:57, Guenter Roeck a écrit :
> On 12/23/2017 05:48 AM, Greg KH wrote:
>> On Sat, Dec 23, 2017 at 06:55:25PM +0800, Yisheng Xie wrote:
>>> Hi all,
>>>
>>> When I tried to use devm_ioremap function and review related code, I 
>>> found
>>> devm_ioremap and devm_ioremap_nocache is almost the same with each 
>>> other,
>>> except one use ioremap while the other use ioremap_nocache.
>>
>> For all arches?  Really?  Look at MIPS, and x86, they have different
>> functions.
>>
> 
> Both mips and x86 end up mapping the same function, but other arches don't.
> mn10300 is one where ioremap and ioremap_nocache are definitely different.

alpha: identical
arc: identical
arm: identical
arm64: identical
cris: different        <==
frv: identical
hexagone: identical
ia64: different        <==
m32r: identical
m68k: identical
metag: identical
microblaze: identical
mips: identical
mn10300: different     <==
nios: identical
openrisc: different    <==
parisc: identical
riscv: identical
s390: identical
sh: identical
sparc: identical
tile: identical
um: rely on asm/generic
unicore32: identical
x86: identical
asm/generic (no mmu): identical

So 4 among all arches seems to have ioremap() and ioremap_nocache() 
being different.

Could we have a define set by the 4 arches on which ioremap() and 
ioremap_nocache() are different, something like 
HAVE_DIFFERENT_IOREMAP_NOCACHE ?

Christophe

> 
> Guenter
> 
>>> While ioremap's
>>> default function is ioremap_nocache, so devm_ioremap_nocache also 
>>> have the
>>> same function with devm_ioremap, which can just be killed to reduce 
>>> the size
>>> of devres.o(from 20304 bytes to 18992 bytes in my compile environment).
>>>
>>> I have posted two versions, which use macro instead of function for
>>> devm_ioremap_nocache[1] or devm_ioremap[2]. And Greg suggest me to kill
>>> devm_ioremap_nocache for no need to keep a macro around for the 
>>> duplicate
>>> thing. So here comes v3 and please help to review.
>>
>> I don't think this can be done, what am I missing?  These functions are
>> not identical, sorry for missing that before.
>>
>> thanks,
>>
>> greg k-h
>>
> 
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