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Date: Mon, 6 Sep 2010 19:55:18 +0900
From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To: akpm@...ux-foundation.org
Cc: sam@...nborg.org, miklos@...redi.hu, jdike@...toit.com,
linux-kernel@...r.kernel.org
Subject: [PATCH] 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@....ntt.co.jp>
---
arch/um/Kconfig.um | 3 +
arch/um/defconfig | 1 -
arch/um/include/asm/dma-mapping.h | 112 -------------------------------------
3 files changed, 3 insertions(+), 113 deletions(-)
delete mode 100644 arch/um/include/asm/dma-mapping.h
diff --git a/arch/um/Kconfig.um b/arch/um/Kconfig.um
index ec2b8da..ffe0934 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
diff --git a/arch/um/defconfig b/arch/um/defconfig
index 6bd456f..564f3de 100644
--- a/arch/um/defconfig
+++ b/arch/um/defconfig
@@ -566,7 +566,6 @@ CONFIG_CRC32=m
# CONFIG_CRC7 is not set
# CONFIG_LIBCRC32C is not set
CONFIG_PLIST=y
-CONFIG_HAS_DMA=y
#
# SCSI device support
diff --git a/arch/um/include/asm/dma-mapping.h b/arch/um/include/asm/dma-mapping.h
deleted file mode 100644
index 1f469e8..0000000
--- a/arch/um/include/asm/dma-mapping.h
+++ /dev/null
@@ -1,112 +0,0 @@
-#ifndef _ASM_DMA_MAPPING_H
-#define _ASM_DMA_MAPPING_H
-
-#include <asm/scatterlist.h>
-
-static inline int
-dma_supported(struct device *dev, u64 mask)
-{
- BUG();
- return(0);
-}
-
-static inline int
-dma_set_mask(struct device *dev, u64 dma_mask)
-{
- BUG();
- return(0);
-}
-
-static inline void *
-dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
- gfp_t flag)
-{
- BUG();
- return((void *) 0);
-}
-
-static inline void
-dma_free_coherent(struct device *dev, size_t size, void *cpu_addr,
- dma_addr_t dma_handle)
-{
- BUG();
-}
-
-static inline dma_addr_t
-dma_map_single(struct device *dev, void *cpu_addr, size_t size,
- enum dma_data_direction direction)
-{
- BUG();
- return(0);
-}
-
-static inline void
-dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
- enum dma_data_direction direction)
-{
- BUG();
-}
-
-static inline dma_addr_t
-dma_map_page(struct device *dev, struct page *page,
- unsigned long offset, size_t size,
- enum dma_data_direction direction)
-{
- BUG();
- return(0);
-}
-
-static inline void
-dma_unmap_page(struct device *dev, dma_addr_t dma_address, size_t size,
- enum dma_data_direction direction)
-{
- BUG();
-}
-
-static inline int
-dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
- enum dma_data_direction direction)
-{
- BUG();
- return(0);
-}
-
-static inline void
-dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nhwentries,
- enum dma_data_direction direction)
-{
- BUG();
-}
-
-static inline void
-dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size,
- enum dma_data_direction direction)
-{
- BUG();
-}
-
-static inline void
-dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nelems,
- enum dma_data_direction direction)
-{
- BUG();
-}
-
-#define dma_alloc_noncoherent(d, s, h, f) dma_alloc_coherent(d, s, h, f)
-#define dma_free_noncoherent(d, s, v, h) dma_free_coherent(d, s, v, h)
-
-static inline void
-dma_cache_sync(struct device *dev, void *vaddr, size_t size,
- enum dma_data_direction direction)
-{
- BUG();
-}
-
-static inline int
-dma_mapping_error(struct device *dev, dma_addr_t dma_handle)
-{
- BUG();
- return 0;
-}
-
-#endif
--
1.7.1
--
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