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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>
This commit is contained in:
FUJITA Tomonori 2010-10-26 14:22:18 -07:00 committed by Linus Torvalds
parent 98c532ecbe
commit d911202e3f
3 changed files with 3 additions and 113 deletions
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3
arch/um/Kconfig.um
View File

@ -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

1
arch/um/defconfig
View File

@ -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

112
arch/um/include/asm/dma-mapping.h
View File

@ -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