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authorBenjamin Gaignard <benjamin.gaignard@linaro.org>2017-01-04 10:12:57 +0100
committerDaniel Vetter <daniel.vetter@ffwll.ch>2017-01-06 11:04:54 +0100
commit62a0d98a188cc4ebd8ea54b37d274ec20465e464 (patch)
treebb649f5cc408727179380fce600adeba99b2ebbd /Documentation/gpu/drm-mm.rst
parent99c48e1e38f0aeaa107ad67c8d91f6c9d9d567a9 (diff)
drm: allow to use mmuless SoC
Some SoC without MMU have display driver where a drm/kms driver could be implemented. Before doing such kind of thing drm/kms must allow to use mmuless devices. This patch propose to remove MMU configuration flag and add a cma helper function to help implementing mmuless display driver version 4: - add documentation about drm_gem_cma_get_unmapped_area() - stub it MMU case Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org> [danvet: Use recommended struct member references in kernel-doc.] Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1483521177-21794-4-git-send-email-benjamin.gaignard@linaro.org
Diffstat (limited to 'Documentation/gpu/drm-mm.rst')
-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
----------------