Commit 955a72ce authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

drm/todo: Clarify situation around fbdev and defio 



The TODO item is misleading and makes it seem as if fbdev emulation
cannot be used with SHMEM. Rephrase the text to describe the current
situation more correctly.

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Acked-by: default avatarNoralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191025092759.13069-3-tzimmermann@suse.de
parent 8e86dee0

Documentation/gpu/todo.rst

+4 −4
Original line number Diff line number Diff line
@@ -206,10 +206,10 @@ Generic fbdev defio support 
---------------------------



The defio support code in the fbdev core has some very specific requirements,

which means drivers need to have a special framebuffer for fbdev. Which prevents

us from using the generic fbdev emulation code everywhere. The main issue is

that it uses some fields in struct page itself, which breaks shmem gem objects

(and other things).

which means drivers need to have a special framebuffer for fbdev. The main

issue is that it uses some fields in struct page itself, which breaks shmem

gem objects (and other things). To support defio, affected drivers require

the use of a shadow buffer, which may add CPU and memory overhead.



Possible solution would be to write our own defio mmap code in the drm fbdev

emulation. It would need to fully wrap the existing mmap ops, forwarding

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