I now got something that works, I have added an iack() callback function in the devices that will return the vector. These are configured from the board driver like this:
	/* FGA-002, Force Gate Array */
	MCFG_FGA002_ADD("fga002", 0)
	MCFG_FGA002_OUT_INT_CB(WRITELINE(fccpu30_state, fga_irq_callback))
	MCFG_FGA002_OUT_LIACK4_CB(DEVREAD8("duscc",  duscc_device, iack))
	MCFG_FGA002_OUT_LIACK5_CB(DEVREAD8("duscc2",  duscc_device, iack))

And there is also an INT callback from the device to the FGA chip like this:
	// DUSCC1&2 interrupt signal REQN is connected to LOCAL IRQ4&5 of the FGA-002 and level is programmable
	MCFG_DUSCC_OUT_INT_CB(DEVWRITELINE("fga002", fga002_device, lirq4_w)) 
	MCFG_DUSCC_OUT_INT_CB(DEVWRITELINE("fga002", fga002_device, lirq5_w))

I would also like to propose an iack() standard api where the vector is returned OR return codes for NO_VECTOR and IACK_TIMEOUT. I have implemented this for the hookup above and will add it to the rest of the devices unless someone tells me that it should be done differently, just let me know.

Last edited by Edstrom; 08/01/16 09:32 AM.

Because I can