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authorKrzysztof Kozlowski <k.kozlowski@samsung.com>2016-08-03 20:46:00 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2016-08-04 12:50:07 (GMT)
commit00085f1efa387a8ce100e3734920f7639c80caa3 (patch)
tree41ff3d6e6884918b4fc4f1ae96a284098167c5b0 /Documentation/DMA-API.txt
parent1605d2715ad2e67ddd0485a26e05ed670a4285ca (diff)
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dma-mapping: use unsigned long for dma_attrs
The dma-mapping core and the implementations do not change the DMA attributes passed by pointer. Thus the pointer can point to const data. However the attributes do not have to be a bitfield. Instead unsigned long will do fine: 1. This is just simpler. Both in terms of reading the code and setting attributes. Instead of initializing local attributes on the stack and passing pointer to it to dma_set_attr(), just set the bits. 2. It brings safeness and checking for const correctness because the attributes are passed by value. Semantic patches for this change (at least most of them): virtual patch virtual context @r@ identifier f, attrs; @@ f(..., - struct dma_attrs *attrs + unsigned long attrs , ...) { ... } @@ identifier r.f; @@ f(..., - NULL + 0 ) and // Options: --all-includes virtual patch virtual context @r@ identifier f, attrs; type t; @@ t f(..., struct dma_attrs *attrs); @@ identifier r.f; @@ f(..., - NULL + 0 ) Link: http://lkml.kernel.org/r/1468399300-5399-2-git-send-email-k.kozlowski@samsung.com Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> Acked-by: Vineet Gupta <vgupta@synopsys.com> Acked-by: Robin Murphy <robin.murphy@arm.com> Acked-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no> Acked-by: Mark Salter <msalter@redhat.com> [c6x] Acked-by: Jesper Nilsson <jesper.nilsson@axis.com> [cris] Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> [drm] Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> Acked-by: Joerg Roedel <jroedel@suse.de> [iommu] Acked-by: Fabien Dessenne <fabien.dessenne@st.com> [bdisp] Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com> [vb2-core] Acked-by: David Vrabel <david.vrabel@citrix.com> [xen] Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> [xen swiotlb] Acked-by: Joerg Roedel <jroedel@suse.de> [iommu] Acked-by: Richard Kuo <rkuo@codeaurora.org> [hexagon] Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> [m68k] Acked-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> [s390] Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org> Acked-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no> [avr32] Acked-by: Vineet Gupta <vgupta@synopsys.com> [arc] Acked-by: Robin Murphy <robin.murphy@arm.com> [arm64 and dma-iommu] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/DMA-API.txt')
-rw-r--r--Documentation/DMA-API.txt33
1 files changed, 14 insertions, 19 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 45ef3f2..1d26eeb6 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -369,35 +369,32 @@ See also dma_map_single().
dma_addr_t
dma_map_single_attrs(struct device *dev, void *cpu_addr, size_t size,
enum dma_data_direction dir,
- struct dma_attrs *attrs)
+ unsigned long attrs)
void
dma_unmap_single_attrs(struct device *dev, dma_addr_t dma_addr,
size_t size, enum dma_data_direction dir,
- struct dma_attrs *attrs)
+ unsigned long attrs)
int
dma_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
int nents, enum dma_data_direction dir,
- struct dma_attrs *attrs)
+ unsigned long attrs)
void
dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sgl,
int nents, enum dma_data_direction dir,
- struct dma_attrs *attrs)
+ unsigned long attrs)
The four functions above are just like the counterpart functions
without the _attrs suffixes, except that they pass an optional
-struct dma_attrs*.
-
-struct dma_attrs encapsulates a set of "DMA attributes". For the
-definition of struct dma_attrs see linux/dma-attrs.h.
+dma_attrs.
The interpretation of DMA attributes is architecture-specific, and
each attribute should be documented in Documentation/DMA-attributes.txt.
-If struct dma_attrs* is NULL, the semantics of each of these
-functions is identical to those of the corresponding function
+If dma_attrs are 0, the semantics of each of these functions
+is identical to those of the corresponding function
without the _attrs suffix. As a result dma_map_single_attrs()
can generally replace dma_map_single(), etc.
@@ -405,15 +402,15 @@ As an example of the use of the *_attrs functions, here's how
you could pass an attribute DMA_ATTR_FOO when mapping memory
for DMA:
-#include <linux/dma-attrs.h>
-/* DMA_ATTR_FOO should be defined in linux/dma-attrs.h and
+#include <linux/dma-mapping.h>
+/* DMA_ATTR_FOO should be defined in linux/dma-mapping.h and
* documented in Documentation/DMA-attributes.txt */
...
- DEFINE_DMA_ATTRS(attrs);
- dma_set_attr(DMA_ATTR_FOO, &attrs);
+ unsigned long attr;
+ attr |= DMA_ATTR_FOO;
....
- n = dma_map_sg_attrs(dev, sg, nents, DMA_TO_DEVICE, &attr);
+ n = dma_map_sg_attrs(dev, sg, nents, DMA_TO_DEVICE, attr);
....
Architectures that care about DMA_ATTR_FOO would check for its
@@ -422,12 +419,10 @@ routines, e.g.:
void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr,
size_t size, enum dma_data_direction dir,
- struct dma_attrs *attrs)
+ unsigned long attrs)
{
....
- int foo = dma_get_attr(DMA_ATTR_FOO, attrs);
- ....
- if (foo)
+ if (attrs & DMA_ATTR_FOO)
/* twizzle the frobnozzle */
....