linux-kernel - Re: [PATCH 00/12] kmap

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Message-Id: <201206252043.53231.arnd@arndb.de>
Date:	Mon, 25 Jun 2012 20:43:52 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Cong Wang <amwang@...hat.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	dhowells <dhowells@...hat.com>
Subject: Re: [PATCH 00/12] kmap_atomic cleanup for 3.6

On Monday 25 June 2012, Peter Zijlstra wrote:
> 
> On Mon, 2012-06-25 at 15:18 +0000, Arnd Bergmann wrote:
> > > Different arch has different values for KM_TYPE_NR, I am not sure if
> > > unifying them to a fixed value could fit all? 
> 
> No you can't. Some arch's have arch specific KM_TYPE thingies, like FRV.

Ah, right. Is it only FRV or are there any others?

> > > For safety, I kept their original values.
> > 
> > My fear is that it will make it harder to clean that code up for
> > real, when there is no longer an indication about where the number
> > comes from.
> 
> Agreed, I'd much prefer it if we'd come up with a sane way to compute
> the max value before doing away with these enums.
> 
> Sadly I haven't been able to come up with a sane way short of whole
> program analysis.

How about putting that constant into asm/highmem.h then, and adding a
default like

#ifndef KM_TYPE_NR
#define KM_TYPE_NR 8
#endif

in linux/highmem.h? Then FRV and anything else that needs it can override
the value and the other ones don't need to bother.

	Arnd
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