From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Mon, 18 Sep 2006 13:55:59 +0000 Subject: Re: [PATCH 2/6] Introduce CONFIG_ZONE_DMA Message-Id: <20060918135559.GB15096@infradead.org> List-Id: References: <20060911222729.4849.69497.sendpatchset@schroedinger.engr.sgi.com> <20060911222739.4849.79915.sendpatchset@schroedinger.engr.sgi.com> In-Reply-To: <20060911222739.4849.79915.sendpatchset@schroedinger.engr.sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Lameter Cc: linux-mm@vger.kernel.org, Nick Piggin , Christoph Hellwig , linux-ia64@vger.kernel.org, Marcelo Tosatti , Arjan van de Ven , Martin Bligh , KAMEZAWA Hiroyuki , Andi Kleen , linux-arch@vger.kernel.org On Mon, Sep 11, 2006 at 03:27:39PM -0700, Christoph Lameter wrote: > Introduce CONFIG_ZONE_DMA > > This patch simply defines CONFIG_ZONE_DMA for all arches. We later do > special things with CONFIG_ZONE_DMA after the VM and an arch are > prepared to work without ZONE_DMA. > > CONFIG_ZONE_DMA can be defined in two ways depending on how > an architecture handles ISA DMA. > > First if CONFIG_GENERIC_ISA_DMA is set by the arch then we know that > the arch needs ZONE_DMA because ISA DMA devices are supported. We > can catch this in mm/Kconfig and do not need to modify arch code. > > Second, arches may use ZONE_DMA in an unknown way. We set CONFIG_ZONE_DMA > for all arches that do not set CONFIG_GENERIC_ISA_DMA in order to insure > backwards compatibility. The arches may later undefine ZONE_DMA > if their arch code has been verified to not depend on ZONE_DMA. Let's pass this on to linux-arch so that the arch maintainers can give input whether they need ZONE_DMA or not. If this just sneaks in unseen I'd bet various architectures will just keept it around despite not needing it.