linux-kernel - Re: [RFC 01/22] Generic show

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Date:	Sat, 05 Apr 2008 01:10:32 +0200
From:	Johannes Weiner <hannes@...urebad.de>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, mingo@...e.hu,
	davem@...emloft.net, hskinnemoen@...el.com, cooloney@...nel.org,
	starvik@...s.com, dhowells@...hat.com, ysato@...rs.sf.net,
	takata@...ux-m32r.org, geert@...ux-m68k.org, ralf@...ux-mips.org,
	kyle@...isc-linux.org, paulus@...ba.org, schwidefsky@...ibm.com,
	lethal@...ux-sh.org, jdike@...toit.com, miles@....org,
	chris@...kel.net, rmk@....linux.org.uk, tony.luck@...el.com
Subject: Re: [RFC 01/22] Generic show_mem() implementation

Hi Sam,

Sam Ravnborg <sam@...nborg.org> writes:

>> >> After more thinking about it, wouldn't it be better to have
>> >> HAVE_ARCH_SHOW_MEM in mm/Kconfig and let archs with their own show_mem()
>> >> select it?  Because there are far more archs that use the generic
>> >> version than those having their own.
>> >
>> > Positive logic is almost always simpler to grasp.
>> > And the usual way to do this is to let arch's select what they
>> > use.
>> > We do not want to have a situation where in most cases we select
>> > a generic version but in some oddball case we select to have
>> > a local version.
>> 
>> I can not follow you.  Of course the arch selects what they use.  But
>> they should not _all_ have to be flagged with an extra select.  So what
>> default-value are you arguing for?
> The normal pattern is to let arch select the generic implmentation they
> use.
> Just because the majority does use the generic version should not
> make us start to use the inverse logic as in your case.
>
> So I want all archs that uses the generic show_mem() to
> do an explicit:
>
> config MYARCH
> 	select HAVE_GENERIC_SHOWMEM
>
> 	Sam

What is the rationale behind this?  It is not a function the arch should
select at all because it is VM code.  The remaining arch-specific
versions are meant to be removed too.

It would be like forcing all architectures to select HAVE_GENERIC_PRINTK
just because one architecture oopses on printk() and needs to replace it
with its own version.

	Hannes
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