[PATCH] optional ZONE_DMA: 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.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Matthew Wilcox <willy@debian.org>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index eaed402ad346..c64973004261 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -7,6 +7,10 @@ config MMU
 	bool
 	default y
 
+config ZONE_DMA
+	bool
+	default y
+
 config LOCKDEP_SUPPORT
 	bool
 	default y