linux-kernel - Re: [patch] kconfig: unify GENERIC_ISA_DMA and ISA_DMA

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Message-ID: <20110126112908.GD2562@n2100.arm.linux.org.uk>
Date:	Wed, 26 Jan 2011 11:29:08 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Kyle McMartin <kyle@...hat.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Randy Dunlap <randy.dunlap@...cle.com>, x86@...nel.org,
	linux-arch@...r.kernel.org, netdev@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] kconfig: unify GENERIC_ISA_DMA and ISA_DMA_API

On Tue, Jan 25, 2011 at 05:06:28PM -0800, David Rientjes wrote:
> CONFIG_GENERIC_ISA_DMA and CONFIG_ISA_DMA_API usually have dependencies
> on one another depending on the architecture and generic kernel code uses
> either to determine whether an ISA-style DMA API is configured.

Wrong.

GENERIC_ISA_DMA enables support for the standard ISA DMA allocator found
in kernel/dma.c

ISA_DMA_API says that a platform supports the ISA DMA interfaces.

An architecture can provide the ISA DMA interfaces, but not use the
standard ISA DMA allocator found in kernel/dma.c.  Such as the one in
arch/arm/kernel/dma.c.

So on ARM, we have platforms where ISA_DMA_API=y but GENERIC_ISA_DMA=n.

> This patch unifies both options and consolidates them into a single
> option: CONFIG_GENERIC_ISA_DMA.  It is also a prerequisite for a 1% text
> savings for a future x86 patch that allows these options to be disabled
> on that architecture when CONFIG_ZONE_DMA also becomes configurable.

NAK.  This is wrong.
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