Mips API

Description

PCSX-Redux has a special API that mips binaries can use :

static __inline__ void pcsx_putc(int c) { *((volatile char* const)0x1f802080) = c; }
static __inline__ void pcsx_debugbreak() { *((volatile char* const)0x1f802081) = 0; }
static __inline__ void pcsx_execSlot(uint8_t slot) { *((volatile uint8_t* const)0x1f802081) = slot; }
static __inline__ void pcsx_exit(int code) { *((volatile int16_t* const)0x1f802082) = code; }
static __inline__ void pcsx_message(const char* msg) { *((volatile char** const)0x1f802084) = msg; }

static __inline__ int pcsx_present() { return *((volatile uint32_t* const)0x1f802080) == 0x58534350; }

Source : https://github.com/grumpycoders/pcsx-redux/blob/main/src/mips/common/hardware/pcsxhw.h#L31-L36

The API needs DEV8/EXP2 (1f802000 to 1f80207f), which holds the hardware register for the bios POST status, to be expanded to 1f8020ff.
Thus the need to use a custom crt0.s if you plan on running your code on real hardware.
The default file provided with the Nugget+PsyQ development environment does that:

_start:
    lw    $t2, SBUS_DEV8_CTRL
    lui   $t0, 8
    lui   $t1, 1
_check_dev8:
    bge   $t2, $t0, _store_dev8
    nop
    b     _check_dev8
    add   $t2, $t1
_store_dev8:
    sw    $t2, SBUS_DEV8_CTRL

Source : https://github.com/grumpycoders/pcsx-redux/blob/main/src/mips/common/crt0/crt0.s#L36-L46

Functions

The following functions are available :

Function	Usage
pcsx_putc(int c)	Print ASCII character with code c to console/stdout.
pcsx_debugbreak()	Break execution (Pause emulation).
pcsx_execSlot(uint8_t slot)	Executes Lua function at PCSX.execSlots[slot]. The slot value can be between 1 and 255. If no Lua function exists within a slot, then this behaves the same as pcsx_debugbreak().
pcsx_exit(int code)	Exit emulator and forward code as exit code.
pcsx_message(const char* msg)	Create a UI dialog displaying msg
pcsx_present()	Returns 1 if code is running in PCSX-Redux

Example of a UI dialog created with pcsx_message() :