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-rw-r--r--Documentation/gpu/drm-mm.rst11
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst
index d3c6d77246cd..1ea94fc86caa 100644
--- a/Documentation/gpu/drm-mm.rst
+++ b/Documentation/gpu/drm-mm.rst
@@ -310,6 +310,17 @@ created.
Drivers that want to map the GEM object upfront instead of handling page
faults can implement their own mmap file operation handler.
+For platforms without MMU the GEM core provides a helper method
+:c:func:`drm_gem_cma_get_unmapped_area`. The mmap() routines will call
+this to get a proposed address for the mapping.
+
+To use :c:func:`drm_gem_cma_get_unmapped_area`, drivers must fill the
+struct :c:type:`struct file_operations <file_operations>` get_unmapped_area
+field with a pointer on :c:func:`drm_gem_cma_get_unmapped_area`.
+
+More detailed information about get_unmapped_area can be found in
+Documentation/nommu-mmap.txt
+
Memory Coherency
----------------