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>

2 files changed, 15 insertions, 20 deletions

diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 45ef3f279c3b..1d26eeb6b5f6 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 */
 	....
 
diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt
index e8cf9cf873b3..2d455a5cf671 100644
--- a/Documentation/DMA-attributes.txt
+++ b/Documentation/DMA-attributes.txt
@@ -2,7 +2,7 @@
 			==============
 
 This document describes the semantics of the DMA attributes that are
-defined in linux/dma-attrs.h.
+defined in linux/dma-mapping.h.
 
 DMA_ATTR_WRITE_BARRIER
 ----------------------