Hello Laurent and all, I am tracking complete files of DU in my source tree linux 4.9 one by one .I know it is not an easy task to study completely but now it is really interesting for me.. first of all I am saying my ultimate goal here,I want to get track the whole route of image/video data until it reaches to final output (Display) ..till now I understand the flow as below FRAME BUFFER ----> CRTC ------> ENCODER ------>CONNECTOR----->DISPLAY By familiarizing DRM I got following knowledge, mainly DRM has its Core(Generic ) and Driver(Specific)..for both of these there are different ioctls. and in the first case most of the ioctls are wrapped through libdrm functions for easiness .. hopping suggestions if I am in wrong path.. On the other side, I think driver dependent APIs will be there right? How various graphics drivers will communicate to DRM? In my limited knowledge, DRM is purely software centric right? so the communication will be through some APIs I think.. expecting a helping hand -- --- Come Let's enjoy the world of Open Source --- Best regards, Stuvart