Hi,

Thanks a lot for that work.

On Sun, Apr 23, 2017 at 06:37:48PM +0800, Icenowy Zheng wrote:

As we are going to add support for the Allwinner DE2 engine in sun4i-drm
driver, we will finally have two types of display engines -- the DE1
backend and the DE2 mixer. They both do some display blending and feed
graphics data to TCON, so I choose to call them both "engine" here.

Abstract the engine type to a new struct with an ops struct, which contains
functions that should be called outside the engine-specified code (in
TCON, CRTC or TV Encoder code).

A dedicated Kconfig option is also added to control whether
sun4i-backend-specified code (sun4i_backend.c and sun4i_layer.c) should
be built. As we removed the codes in CRTC code that directly call the
layer code, we can now extract the layer part and combine it with the
backend part into a new module, sun4i-backend.ko.

While the code itself is good now, the patch mixes a few things that
would be better to be split in separate patches. I think it would be
better if you had patches organized like this:
  - Abstract the engine type by create the sunxi_engine structure and
    fixing all the callers.
  - Move the layers and backend files in the same module, and remove
    the now useless EXPORT_SYMBOLS.
  - Create a Kconfig option.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com