Delving into graphics HAL

After we have an overview of graphics system architecture, we will analyze the Gralloc module, which is the graphics HAL. In the AOSP source code, the skeleton of Gralloc HAL implementation can be found at the following folder:

$AOSP/hardware/libhardware/modules/gralloc

This is a general implementation that provides a reference for developers to create their own Gralloc module. Gralloc will access framebuffer and GPU to provide services to the upper layer. In this section, we will analyze this general implementation first. After the analysis of this general Gralloc HAL module, we will introduce the Gralloc HAL of the Android emulator.

Loading the Gralloc module

When application developers draw images to the screen, there are two ways to do it. They can use Canvas or OpenGL. Beginning in Android 4.0, both methods use hardware acceleration by default. To use hardware acceleration, we need to use Open GL libraries and eventually the Gralloc module will be loaded as part...