yuanyuanli85 / HalSample

Sample code to show how to do modularization

Hal layers Sample

This sample try to figure out a way to solve the modularization problem in hal layers and how to avoid platform code referred by common files.

####Problem to solve In this sample, we use two interfaces get_platform_id() and submit_command() to show how to do modularization.

• get_platform_id() is a platform specific function to return platform id
• submit_command() is a platform specific function to submit commands. Each platform should have its own implementation.
• submit_x_engine() is a function only available from gen10+
• load_kernel_binary() is a common function, not platform related.

####Key ideas

• Class Using multiple-layer hierarchy will bring casting effort in running time and let the code to invoke complex. To solve this problem, we put the limitation for class hierarchy, only two-layer allowed.

####Code Structure

• HalBase.cpp & HalBase.h Base class . common functions and non-platform code should be defined in common layers. Platform class should derive from base class, i.e HalGen9 and HalGen11. get_platform_id() returns the platform id submit_command() will be overridden by the method defined in derived class. if this method not defined in derived class, base class one will be used which does nothing.

• HalGen9.cpp & HalGen11.cpp Platform-specific class derived from HalBase. submit_command() is not defined in HalGen11.cpp to simulate the behavior of not-implemented functions on platform

• haldemox.cpp Code to simulate how to create instances of platform-classes and how to invoke interfaces at running time.

####How to avoid moving everything to C++ The cost will be very huge if we move everything to C++. It is better to keep C interfaces.

• Common functions: keep as C interfaces
• Platform related functions: provide C interface to access.

```
int HalCm_Submit_Command(pState)  
{ 
	return pState->phal->submit_command();  
}  
```

####How to solve the platform files directly refered by common files There are two violations in previous solution.

• The definition of HalGen9 and HalGen11 have to be included in HalBase.h
• The instantiation code in common layer are not removed.

We use custom build in Cmake to dynamically generate the header HalInit.h and instantiation code init(). The python scripts locates in scripts\HeaderGenerator.py whose input is the list of supported platforms.

Command to build code supports Gen9, Gen10 and Gen11 $cmake -Wno-dev -G "Visual Studio %CMAKE_MODE_VS%%CMAKE_ARCH%" %BUILD_ROOT% -DGEN9=1 -DGEN10=1 -DGEN11=1
Command to build code supports Gen10 and Gen11 $cmake -Wno-dev -G "Visual Studio %CMAKE_MODE_VS%%CMAKE_ARCH%" %BUILD_ROOT% -DGEN10=1 -DGEN11=1