linux-kernel - Re: [PATCH] ata: libata depends on HAS

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Message-ID: <4A0D5051.90708@gmail.com>
Date:	Fri, 15 May 2009 20:21:53 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	hancockrwd@...il.com, alan@...rguk.ukuu.org.uk, flar@...andria.com,
	schmitz@...phys.uni-duesseldorf.de, linux-kernel@...r.kernel.org,
	jgarzik@...ox.com, linux-ide@...r.kernel.org,
	takata@...ux-m32r.org, geert@...ux-m68k.org,
	linux-m68k@...r.kernel.org, ysato@...rs.sourceforge.jp
Subject: Re: [PATCH] ata: libata depends on HAS_DMA

Hello,

Arnd Bergmann wrote:
> On Friday 15 May 2009, Tejun Heo wrote:
>> FUJITA Tomonori wrote:
>>> Can libata call dma_supported() per device to decide DMA or PIO mode?
>>> Then, we can solve this problem by add dummy DMA API (just calls BUG)
>>> on such architectures, without Kconfig magic or adding ifdef (like the
>>> old ide stack does), I think.
> 
> That would be the !CONFIG_PCI half of the old
> include/asm-generic/dma-mapping.h file that you just removed,
> right?
> 
> In general, I'd prefer keeping the asm-generic/dma-mapping-broken.h
> implementation that gives us a compile-time error, but maybe there
> is an even better option based on the mn10300 implementation which
> basically pretends everything works with just page_to_phys() mappings.

Don't know much history here but I don't wanna sprinkle ifdefs around
in libata so I would much prefer dummy implementation which doesn't
fail compile.

>> Sure it can.  Which specific drivers are we talking about?
> 
> The main problem is libata-core.c, which references DMA mapping
> API calls that are only implemented on architectures setting
> CONFIG_HAS_DMA.

Yeah, sure, libata-core is used by every driver but I was wondering
whether only SFF drivers are of interest or there are others.

Thanks.

-- 
tejun
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