Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

Introduction to Hardware Abstraction Layers for SOC 181
Figure 14-3 shows an example of HAL API function for context switch,
_cxt_switch(cxt_type oldcxt, cxt_type newcxt). The function can be used for
context switch on any processors. For a specific processor, we need to implement
the body of the function. Figure 14-3 shows also the real code of the
HAL API function for ARM7 processor.
Since the HAL API gives an abstraction of underlying HW architecture,
when the OS or application SW is designed using the HAL API, the SW code
is portable as far as the HAL API can be implemented on the underlying HW
architecture. Thus, conventionally, the HAL has been used to ease OS porting
on new HW architectures.
3. RELATED WORK
There are similar concepts to HAL: nano-kernel and device driver. Nanokernel
is usually defined to be an ensemble of interrupt service routines and
task stacks [4]. It serves as a foundation where a micro-kernel can be built.
In this definition, nano-kernel can be considered to be a part of HAL since it