The talk will cover the current state of Explicit Fencing on Graphics. It first appeared on Linux as the Android Sync Framework to improve buffer handling between Kernel Drivers and the HWComposer. With explicit fencing userspace is responsible for synchronize between drivers sharing the same DMA buffer. It gets the buffers' fence from the Producer driver(GPU or Camera) and send it to the Consumer one (DRM) and vice-versa. The Consumer then wait the fence to signal before using the buffer. The fence signal when the buffer is ready for use, eg: When the GPU finishes processing it., the fence signal and the DRM driver can show it on screen.

Before only Implicit Fencing existed, where the kernel handles fencing between drivers internally with no userspace interference. There was no generic code, as each driver hacked its own implicit fencing mechanism, leading to hard to debug bugs.