[PATCH 2/2] drm/todo: Clarify situation around fbdev and defio

[Noralf Trønnes]

Den 25.10.2019 11.27, skrev Thomas Zimmermann:
> 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
> --- 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.
>  

Ah yes, there's a todo on this. Look good to me:

Acked-by: Noralf Trønnes <noralf at tronnes.org>

>  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
>