The input/output processor (IOP) drivers

[frno7]

The input/output processor (IOP) is a MIPS R3000A, or in later PlayStation 2 models a PowerPC 405GP emulating a MIPS R3000A. This processor provides a number of kernel services, for example handling of USB OHCI interrupts.

• The IOP relocatable executable (IRX) modules need to be loaded and possibly unloaded by drivers. Represent IRX modules as kernel firmware;
• Representation IOP modules in a sysfs pseudo file system with statistics on loaded IRX modules;
• Display amount of free IOP memory in sysfs?
• Is a specific IOP device driver such as /dev/iop useful, for example to freely read and write IOP addresses?
• Use the PowerPC 405GP hardware directly, underneath its normal MIPS R3000A emulation.

[sp193]

The PPC was not officially meant for us to control (there is no documentation for it). But as it has been proven, it is possible to change how it works because the EE can actually write to its RAM.

[frno7]

Do you have links or other information on the details of this RAM access? That would be most helpful, should someone decide to proceed to directly control the PowerPC.

[uyjulian]

You can probably find those information on psx-scene, assemblergames, or psx-place.
This might help: http://psx-scene.com/forums/f19/deckard-ppc-iop-discussion-157416/

[uyjulian]

Here's a WIP IOP firmware reimplementation: https://github.com/uyjulian/ps2iop
Currently, function stubs are implemented and not much else.
I plan on starting with modules from SDK 1.3.4 and adding features from SDK 3.1.0 whenever possible.
Another useful resource for IOP modules are fps2bios from PCSX2.

[frno7]

Many thanks, @uyjulian!