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-rw-r--r--Documentation/driver-api/device-io.rst9
1 files changed, 5 insertions, 4 deletions
diff --git a/Documentation/driver-api/device-io.rst b/Documentation/driver-api/device-io.rst
index 2c7abd234f..d55384b106 100644
--- a/Documentation/driver-api/device-io.rst
+++ b/Documentation/driver-api/device-io.rst
@@ -408,11 +408,12 @@ functions for details on the CPU side of things.
ioremap_uc()
------------
-ioremap_uc() behaves like ioremap() except that on the x86 architecture without
-'PAT' mode, it marks memory as uncached even when the MTRR has designated
-it as cacheable, see Documentation/arch/x86/pat.rst.
+ioremap_uc() is only meaningful on old x86-32 systems with the PAT extension,
+and on ia64 with its slightly unconventional ioremap() behavior, everywhere
+elss ioremap_uc() defaults to return NULL.
-Portable drivers should avoid the use of ioremap_uc().
+
+Portable drivers should avoid the use of ioremap_uc(), use ioremap() instead.
ioremap_cache()
---------------