From 955a72cea507051e366a4b70de86d974565bfe93 Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Fri, 25 Oct 2019 11:27:59 +0200 Subject: [PATCH] drm/todo: Clarify situation around fbdev and defio MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: Thomas Zimmermann Acked-by: Noralf Trønnes Link: https://patchwork.freedesktop.org/patch/msgid/20191025092759.13069-3-tzimmermann@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 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -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