October 7, 2016 - Chris Michael
Introducing the New & Improved Ecore_Drm2 Library
In the early days of developing Wayland support in EFL/Enlightenment, it was quickly apparent that EFL would need an abstraction library to interface with libdrm. We wanted users of EFL to be able to call simple functions without having to know about the underlying internals of libdrm, thus the original Ecore_Drm library was born. First, efforts to develop this library were undertaken with much enthusiasm and little fan-fare. After the birth of Ecore_Drm, we then proceeded to integrate it’s usage into some new Evas and Ecore_Evas engines so that the Enlightenment Desktop Shell could make use of it and render our first standalone Wayland desktop implementation.
After kicking the tires of our Wayland desktop for a while, we came to realize some shortcomings of the existing Ecore_Drm implementation. For starters, it would create it’s own Ecore_Drm_Device structure when launching the Enlightenment Wayland desktop (this structure was a representation of the physical connection to the /dev/dri card used in rendering). Along with this structure came lists of outputs, inputs, seats, planes, etc. In short, this structure was not very light and memory was being used up needlessly. Other shortcomings of the Ecore_Drm library included things such as structures being declared in public headers that couldn’t be easily changed, input device handling, systemd/logind support being coded directly into the library, and several other issues.
Redesigning From the Ground up
The community came to the easy decision that a better implementation was needed, thus we started efforts to create a new implementation and the Ecore_Drm2 library was born. This new library was developed slowly, while taking into account the shortcomings of the first iteration because we didn’t want to repeat the mistakes of the past. To help avoid these mistakes, the Ecore_Drm2 library API is currently marked as a ‘beta’ API which means it’s susceptible to changes at any time until the beta API marking is removed.
After several months of careful development and several months of testing, Ecore_Drm2 was deemed stable and complete enough to be pushed upstream. Efforts then ensued to modify the existing Evas and Ecore_Evas engines to use this shiny new library.
The new Ecore_Drm2 library fixes all of the shortcomings of the previous library. The community decided at inception that input handling should reside in it’s own library (thus the elput library was created). This removed a lot of internal overhead inside the Ecore_Drm2 library while also removing the need for the library itself to interface with systemd/logind. Public structures exposed via the Ecore_Drm2 library now have their actual implementations kept private so that changes could be made in the future if necessary. Internally, the size of the Ecore_Drm2_Device structure has been greatly reduced, saving memory.
While many improvements have been made to this new library (compared to the old one), one of the greatest overall improvements came as a result of it’s existence. With the new version of this library, we realized that the Evas and Ecore_Evas drm engines were also ripe for improvement. These rendering improvements did not happen by accident, but rather are the result of some great efforts, led by Derek Foreman, that provided tangible benefits by reducing tearing, decreasing time to first frame, improving rendering speed, and reducing memory usage. We believe we will see many more improvements just like this as a result of Ecore_Drm2.
About Chris Michael
Chris Michael has been an EFL/Enlightenment developer for over 13 years and is now working for the Samsung Open Souce Group. Among his many ongoing projects include his work to port the Enlightenment Foundation Libraries to the Wayland protocol, porting the Tizen Window Manager to use the Wayland protocol, and writing an IRC client which will function using the Wayland protocol. He has given several talks at various LinuxCon events all around the globe, generally focused on Wayland.
Image Credits: EFL Project