Difference between HAL and Drivers

Question

Following to my post I'd like to know what's the difference between drivers and HAL ?

Answer 1

From this doc:

HAL The hardware abstraction layer defines the standard interface that the camera service calls into and that you must implement to have your camera hardware function correctly.

Kernel driver The camera's driver interacts with the actual camera hardware and your implementation of the HAL. The camera and driver must support YV12 and NV21 image formats to provide support for previewing the camera image on the display and video recording.