Hi, > > I'm trying to write a driver for a custom extension bus > > mapped in my MPC8248 > > memory space. > > > > The bus has 32 interrupt lines which are handled by an > > interrupt controller > > connected to a single external interrupt on the MPC8248. > > > > I've had a look at the Linux interrupt management code, but > > haven't found any > > easy API to add an external interrupt controller. Could > > No, the linux kernel has this feature. > > > someone give me a few > > pointers regarding how to proceed ? I would like to > > "register" the interrupt > > controller with the interrupt management core, so that > > request_irq()/free_irq() could be used with the extra interrupts. > > Need define the struct hw_interrupt_type <your_interrupt_controller> > and the struct irqaction <your_irqaction>, and > implement member function and hook your interrupt controller to > The interrupt controller of MPC8248 with setup_irq.
I've had a deeper look at that approach and things are, if not entirely clear, at least clear enough to try coding a simple interrupt controller. There is, though, something that bothers me. My interrupt controller has 32 IRQ lines. If I hook up my interrupt controller using the ppc_md.init_IRQ and ppc_md.get_irq callbacks, only one interrupt will be processed at a time. The interrupt handler acks the interrupt at source, but other interrupts which are already flagged will reinterrupt the CPU as soon as the interrupt handler returns. This is clearly sub-optimal. I noticed that some people call __do_IRQ reintrantly (in arch/ppc/syslib/m82xx_pic.c for instance). Could I do that as well, or is that discouraged ? Any problem regarding the stack size ? Thanks for your help. Best regards, Laurent Pinchart
