dma: add dma_*map*_attrs() interfaces

Introduce new interfaces, dma_*map*_attrs(), for passing architecture-specific
attributes when memory is mapped and unmapped for DMA.  Give the interfaces
default implementations which ignore attributes.  Also introduce the
dma_{set|get}_attr() interfaces for setting and retrieving individual
attributes.  Define one attribute, DMA_ATTR_WRITE_BARRIER, in anticipation of
its use by ia64/sn.  Select whether architectures implement arch-specific
versions of the dma_*map*_attrs() interfaces via HAVE_DMA_ATTRS in Kconfig.

[[email protected]: dma_{set,get}_attr() have to be static inline]
Signed-off-by: Arthur Kepner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Jesse Barnes <[email protected]>
Cc: Jes Sorensen <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Roland Dreier <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: David Miller <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Grant Grundler <[email protected]>
Cc: Michael Ellerman <[email protected]>
Signed-off-by: Mark Nelson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

arch/Kconfig

@@ -36,3 +36,6 @@ config HAVE_KPROBES
 
 config HAVE_KRETPROBES
 	def_bool n
+
+config HAVE_DMA_ATTRS
+	def_bool n

arch/ia64/Kconfig

@@ -19,6 +19,7 @@ config IA64
 	select HAVE_OPROFILE
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
+	select HAVE_DMA_ATTRS
 	select HAVE_KVM
 	default y
 	help

include/linux/dma-attrs.h

@@ -0,0 +1,74 @@
+#ifndef _DMA_ATTR_H
+#define _DMA_ATTR_H
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/bug.h>
+
+/**
+ * an enum dma_attr represents an attribute associated with a DMA
+ * mapping. The semantics of each attribute should be defined in
+ * Documentation/DMA-attributes.txt.
+ */
+enum dma_attr {
+	DMA_ATTR_WRITE_BARRIER,
+	DMA_ATTR_MAX,
+};
+
+#define __DMA_ATTRS_LONGS BITS_TO_LONGS(DMA_ATTR_MAX)
+
+/**
+ * struct dma_attrs - an opaque container for DMA attributes
+ * @flags - bitmask representing a collection of enum dma_attr
+ */
+struct dma_attrs {
+	unsigned long flags[__DMA_ATTRS_LONGS];
+};
+
+#define DEFINE_DMA_ATTRS(x) 					\
+	struct dma_attrs x = {					\
+		.flags = { [0 ... __DMA_ATTRS_LONGS-1] = 0 },	\
+	}
+
+static inline void init_dma_attrs(struct dma_attrs *attrs)
+{
+	bitmap_zero(attrs->flags, __DMA_ATTRS_LONGS);
+}
+
+#ifdef CONFIG_HAVE_DMA_ATTRS
+/**
+ * dma_set_attr - set a specific attribute
+ * @attr: attribute to set
+ * @attrs: struct dma_attrs (may be NULL)
+ */
+static inline void dma_set_attr(enum dma_attr attr, struct dma_attrs *attrs)
+{
+	if (attrs == NULL)
+		return;
+	BUG_ON(attr >= DMA_ATTR_MAX);
+	__set_bit(attr, attrs->flags);
+}
+
+/**
+ * dma_get_attr - check for a specific attribute
+ * @attr: attribute to set
+ * @attrs: struct dma_attrs (may be NULL)
+ */
+static inline int dma_get_attr(enum dma_attr attr, struct dma_attrs *attrs)
+{
+	if (attrs == NULL)
+		return 0;
+	BUG_ON(attr >= DMA_ATTR_MAX);
+	return test_bit(attr, attrs->flags);
+}
+#else /* !CONFIG_HAVE_DMA_ATTRS */
+static inline void dma_set_attr(enum dma_attr attr, struct dma_attrs *attrs)
+{
+}
+
+static inline int dma_get_attr(enum dma_attr attr, struct dma_attrs *attrs)
+{
+	return 0;
+}
+#endif /* CONFIG_HAVE_DMA_ATTRS */
+#endif /* _DMA_ATTR_H */

include/linux/dma-mapping.h

@@ -146,4 +146,21 @@ static inline void dmam_release_declared_memory(struct device *dev)
 }
 #endif /* ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY */
 
+#ifndef CONFIG_HAVE_DMA_ATTRS
+struct dma_attrs;
+
+#define dma_map_single_attrs(dev, cpu_addr, size, dir, attrs) \
+	dma_map_single(dev, cpu_addr, size, dir)
+
+#define dma_unmap_single_attrs(dev, dma_addr, size, dir, attrs) \
+	dma_unmap_single(dev, dma_addr, size, dir)
+
+#define dma_map_sg_attrs(dev, sgl, nents, dir, attrs) \
+	dma_map_sg(dev, sgl, nents, dir)
+
+#define dma_unmap_sg_attrs(dev, sgl, nents, dir, attrs) \
+	dma_unmap_sg(dev, sgl, nents, dir)
+
+#endif /* CONFIG_HAVE_DMA_ATTRS */
+
 #endif