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-rw-r--r--include/asm-generic/io.h30
1 files changed, 29 insertions, 1 deletions
diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index f56094cfdeff..eed3bbe88c8a 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -736,6 +736,35 @@ static inline void *phys_to_virt(unsigned long address)
}
#endif
+/**
+ * DOC: ioremap() and ioremap_*() variants
+ *
+ * If you have an IOMMU your architecture is expected to have both ioremap()
+ * and iounmap() implemented otherwise the asm-generic helpers will provide a
+ * direct mapping.
+ *
+ * There are ioremap_*() call variants, if you have no IOMMU we naturally will
+ * default to direct mapping for all of them, you can override these defaults.
+ * If you have an IOMMU you are highly encouraged to provide your own
+ * ioremap variant implementation as there currently is no safe architecture
+ * agnostic default. To avoid possible improper behaviour default asm-generic
+ * ioremap_*() variants all return NULL when an IOMMU is available. If you've
+ * defined your own ioremap_*() variant you must then declare your own
+ * ioremap_*() variant as defined to itself to avoid the default NULL return.
+ */
+
+#ifdef CONFIG_MMU
+
+#ifndef ioremap_uc
+#define ioremap_uc ioremap_uc
+static inline void __iomem *ioremap_uc(phys_addr_t offset, size_t size)
+{
+ return NULL;
+}
+#endif
+
+#else /* !CONFIG_MMU */
+
/*
* Change "struct page" to physical address.
*
@@ -743,7 +772,6 @@ static inline void *phys_to_virt(unsigned long address)
* you'll need to provide your own definitions.
*/
-#ifndef CONFIG_MMU
#ifndef ioremap
#define ioremap ioremap
static inline void __iomem *ioremap(phys_addr_t offset, size_t size)

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