Using CFW API in your homebrew
Epinephrine CFW offers five libraries that can be used by homebrew software: SystemCtrlForKernel, SystemCtrlForUser, KUBridge, SysclibForUser, and VshCtrlLib.
The SystemCtrlForKernel and SystemCtrlForUser contain API that allows the user to launch/execute homebrew and games, get and set system information, live patching utilities, and more. It is available in all possible runlevels, but, as the names suggest, SystemCtrlForKernel is only available for kernel plugins, while SystemCtrlForUser is available for user plugins and homebrew applications.
The KUBridge provides APIs to execute functions with kernel access from the user-space. It is also available in all possible runlevels, and as SystemCtrlForUser, it is available for user plugins and homebrew applications.
The SysclibForUser provides many basic C library API to the user-space. With it, you can avoid linking to the newlibc implementation of those functions, making your executable smaller. It is available in all possible runlevels for user plugins and homebrew applications.
The VshCtrlLib extends the API available on the VSH/XMB runlevel; this also means it is only available on that runlevel. It is available for user plugins.
How to use them in your project
To start using these APIs, you can install the PSP CFW SDK to obtain the headers and the stubs for the CFW API.
The easiest way is to use psp-pacman:
psp-pacman -Syy psp-cfw-sdk
You can also install it from source, by cloning the git repo linked above, and executing
make install
warning
PSPDEV toolchain must be properly set for it to work.
My homebrew already uses CFW APIs
In the case of your homebrew already using CFW APIs, there is a very good chance that you won’t need to modify a thing to support Epinephrine.
The Epinephrine’s SystemCtrlForUser and KUBridge have 100% API compatibility with the same libraries of M33, ME, PRO, and ARK custom firmwares. That means that if the API provided by the original targeted CFW is sufficient for your project, you won’t need to change the stubs and header and create a build only targeted to Epinephrine. You will only need to change if you desire to access newly added APIs.
The Epinephrine’s SystemCtrlForKernel is mostly compatible with M33, ME, PRO, and ARK custom firmwares. Make sure that any function you use from this library also exists for Epinephrine. If you couldn’t find any, at worst, you will need to rebuild your kernel plugin project for the 6.61 PSP firmware version to support Epinephrine.
The Epinephrine’s SysclibForUser only exists on Epinephrine and ARK, and they have total parity. If you already use it, you don’t need to change.
The Epinephrine’s VshCtrlLib is 100% compatible with M33, and mostly compatible with ME, PRO, and ARK custom firmwares. Make sure that any function you use from this library also exists for Epinephrine. If you couldn’t find any, you don’t need to change a thing to support Epinephrine.