opensbi/docs/platform_guide.md

OpenSBI Platform Support Guideline
==================================

The OpenSBI platform support allows an implementation to define a set of
platform-specific hooks (hardware manipulation functions) in the form of a
*struct sbi_platform* data structure instance. This instance is required by
the platform-independent *libsbi.a* to execute platform-specific operations.

Each of the reference platform supports provided by OpenSBI defines an instance
of the *struct sbi_platform* data structure. For each supported platform,
*libplatsbi.a* integrates this instance with *libsbi.a* to create a
platform-specific OpenSBI static library. This library is installed
in *<install_directory>/platform/<platform_subdir>/lib/libplatsbi.a*

OpenSBI also provides implementation examples of bootable runtime firmwares for
the supported platforms. These firmwares are linked against *libplatsbi.a*.
Firmware binaries are installed in
*<install_directory>/platform/<platform_subdir>/bin*. These firmwares can be
used as executable runtime firmwares on the supported platforms as a replacement
for the legacy *riscv-pk* boot loader (BBL).

A complete doxygen-style documentation of *struct sbi_platform* and related
APIs is available in the file *include/sbi/sbi_platform.h*.

Adding support for a new platform
---------------------------------

Support for a new platform named *&lt;xyz&gt;* can be added as follows:

1. Create a directory named *&lt;xyz&gt;* under the *platform/* directory.
2. Create platform configuration files named *Kconfig* and *configs/defconfig*
   under the *platform/&lt;xyz&gt;/* directory. These configuration files will
   provide the build time configuration for the sources to be compiled.
3. Create a *platform/&lt;xyz&gt;/objects.mk* file for listing the platform
   object files to be compiled. This file also provides platform-specific
   compiler flags, and select firmware options.
4. Create a *platform/&lt;xyz&gt;/platform.c* file providing a
   *struct sbi_platform* instance.

A platform support code template is available under the *platform/template*
directory. Copying this directory and its content as a new directory named
*&lt;xyz&gt;* under the *platform/* directory will create all the files
mentioned above.