It seems a DEV9 IOP module is needed, for various expansion bay hardware. A prototype has been implemented in module/dev9.c, to support a harddisk driver. Important DEV9 registers are only available from the IOP, so the EE cannot easily manage DEV9 by itself, as it seems. Furthermore, DEV9 resources need to be shared among multiple devices, such as harddisk and network. Plan:

• identify attached DEV9 hardware;
• power off DEV9 if it isn’t used;
• power on DEV9 if some driver needs it;
• initialise DEV9 registers as needed;
• share, acknowledge and mask DEV9 interrupts as needed;
• document DEV9 registers, etc. (is there some reliable source?).