linux-kernel - Re: [PATCH] x86: adjust GFP mask handling for coherent allocations

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Message-Id: <4AE6C4D3020000780001BF13@vpn.id2.novell.com>
Date:	Tue, 27 Oct 2009 09:00:51 +0000
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Yinghai Lu" <yinghai@...nel.org>, <tglx@...utronix.de>,
	"Takashi Iwai" <tiwai@...e.de>, <linux-kernel@...r.kernel.org>,
	<jbarnes@...tuousgeek.org>, <hpa@...or.com>
Subject: Re: [PATCH] x86: adjust GFP mask handling for coherent
	 allocations

>>> Ingo Molnar <mingo@...e.hu> 26.10.09 21:19 >>>
>
>* Jan Beulich <JBeulich@...ell.com> wrote:
>
>> >>> Ingo Molnar <mingo@...e.hu> 26.10.09 16:22 >>>
>> >* Jan Beulich <JBeulich@...ell.com> wrote:
>> >> And any attempt to eliminate the conditional another way would just 
>> >> introduce a very similar conditional elsewhere; with this having a 
>> >> single user (and foreseeably not ever a second one) I would think this 
>> >> would just make the code less readable.
>> >
>> >There's 3 other current uses of DMA_BIT_MASK(24) in arch/x86 - couldnt 
>> >those use ISA_DMA_BIT_MASK too?
>> 
>> Oh, so you didn't mean me to eliminate the conditional in pci-dma.c, 
>> but just to replace the DMA_BIT_MASK(24) here an elsewhere. Sure, I'm 
>> fine with adding this to the patch.
>
>Well, can ISA_BIT_MASK fall back to DMA_BIT_MASK(32) on !CONFIG_ISA? If 
>we have ISA support disabled we might as well pretend the whole world is 
>PCI, right?
>
>That way we'd get rid of that #ifdef in the .c code too.

I can certainly code it that way, but then we can't use it to replace any
instance of DMA_BIT_MASK(24) used to derive the need for GFP_DMA.
So I'm not sure elimination of which of the instances of DMA_BIT_MASK(24)
is more desirable...

Jan

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