[PATCH 2/2] drm/todo: Clarify situation around fbdev and defio
tzimmermann at suse.de
Fri Oct 25 09:27:59 UTC 2019
The TODO item is misleading and makes it seem that fbdev emulation
cannot be used with SHMEM. Rephrase the text to describe the current
situation more correctly.
Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Documentation/gpu/todo.rst | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 73c51b5a0997..6792fa9b6b6b 100644
@@ -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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