Commit d911202e authored by FUJITA Tomonori's avatar FUJITA Tomonori Committed by Linus Torvalds
Browse files

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: default avatarFUJITA 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 98c532ec

arch/um/Kconfig.um

+3 −0
Original line number Diff line number Diff line
@@ -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

arch/um/defconfig

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/um/include/asm/dma-mapping.h

deleted100644 → 0
+0 −112
Original line number Diff line number Diff line 
#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

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