From 62a0d98a188cc4ebd8ea54b37d274ec20465e464 Mon Sep 17 00:00:00 2001 From: Benjamin Gaignard Date: Wed, 4 Jan 2017 10:12:57 +0100 Subject: 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 [danvet: Use recommended struct member references in kernel-doc.] Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1483521177-21794-4-git-send-email-benjamin.gaignard@linaro.org --- Documentation/gpu/drm-mm.rst | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'Documentation/gpu') 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 ` 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 ---------------- -- cgit v1.2.3