arch: introduce memremap()
Existing users of ioremap_cache() are mapping memory that is known in
advance to not have i/o side effects. These users are forced to cast
away the __iomem annotation, or otherwise neglect to fix the sparse
errors thrown when dereferencing pointers to this memory. Provide
memremap() as a non __iomem annotated ioremap_*() in the case when
ioremap is otherwise a pointer to cacheable memory. Empirically,
ioremap_<cacheable-type>() call sites are seeking memory-like semantics
(e.g. speculative reads, and prefetching permitted).
memremap() is a break from the ioremap implementation pattern of adding
a new memremap_<type>() for each mapping type and having silent
compatibility fall backs. Instead, the implementation defines flags
that are passed to the central memremap() and if a mapping type is not
supported by an arch memremap returns NULL.
We introduce a memremap prototype as a trivial wrapper of
ioremap_cache() and ioremap_wt(). Later, once all ioremap_cache() and
ioremap_wt() usage has been removed from drivers we teach archs to
implement arch_memremap() with the ability to strictly enforce the
mapping type.
Cc: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/include/linux/io.h b/include/linux/io.h
index fb5a998..3fcf625 100644
--- a/include/linux/io.h
+++ b/include/linux/io.h
@@ -121,4 +121,13 @@
#endif
#endif
+enum {
+ /* See memremap() kernel-doc for usage description... */
+ MEMREMAP_WB = 1 << 0,
+ MEMREMAP_WT = 1 << 1,
+};
+
+void *memremap(resource_size_t offset, size_t size, unsigned long flags);
+void memunmap(void *addr);
+
#endif /* _LINUX_IO_H */