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authorFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>2010-10-26 14:22:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-26 16:52:12 -0700
commitd911202e3f722c29065942400ea108b7096bdac7 (patch)
tree17c0a4c8d2fa36db4469ddb21e7edee29184df74 /arch/um/Kconfig.um
parent98c532ecbe582586e204688c6cde7e27580cc43f (diff)
uml: define CONFIG_NO_DMA
I think that it's better to detect DMA misuse at build time rather than calling BUG_ON. Architectures that can't do DMA need to define CONFIG_NO_DMA. Thanks to Sam Ravnborg for explaining how CONFIG_NO_DMA and CONFIG_HAS_DMA work: http://marc.info/?l=linux-kernel&m=128359913825550&w=2 HAS_DMA is defined like this: config HAS_DMA boolean depends on !NO_DMA default y So to set HAS_DMA to true an arch should do: 1) Do not define NO_DMA 2) Define NO_DMA abd set it to 'n' Must archs - including um - used principle 1). In the um case we want to say that we do NOT have any DMA. This can be done in two ways. a) define NO_DMA and set it to 'y' b) redefine HAS_DMA and set it to 'n'. The patch you provided used principle b) where other archs use principle a). So I suggest you should use principle a) for um too. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Jeff Dike <jdike@addtoit.com> Cc: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/um/Kconfig.um')
-rw-r--r--arch/um/Kconfig.um3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/um/Kconfig.um b/arch/um/Kconfig.um
index ec2b8da1aba..ffe0934a3cc 100644
--- a/arch/um/Kconfig.um
+++ b/arch/um/Kconfig.um
@@ -147,3 +147,6 @@ config KERNEL_STACK_ORDER
This option determines the size of UML kernel stacks. They will
be 1 << order pages. The default is OK unless you're running Valgrind
on UML, in which case, set this to 3.
+
+config NO_DMA
+ def_bool y