Re: User mode drivers: part 1, interrupt handling (patch for 2.6.11)

Alan Cox
2005-03-11T19:21:26Z

On Gwe, 2005-03-11 at 03:36, Peter Chubb wrote:
> +static irqreturn_t irq_proc_irq_handler(int irq, void *vidp, struct pt_regs *regs)
> +{
> + struct irq_proc *idp = (struct irq_proc *)vidp;
> +
> + BUG_ON(idp->irq != irq);
> + disable_irq_nosync(irq);
> + atomic_inc(&idp->count);
> + wake_up(&idp->q);
> + return IRQ_HANDLED;

You just deadlocked the machine in many configurations. You can't use
disable_irq for this trick you have to tell the kernel how to handle it.
I posted a proposal for this sometime ago because X has some uses for
it. The idea being you'd pass a struct that describes

1. What tells you an IRQ occurred on this device
2. How to clear it
3. How to enable/disable it.

Something like

struct {
u8 type; /* 8, 16, 32 I/O or MMIO */
u8 bar; /* PCI bar to use */
u32 offset; /* Into bar */
u32 mask; /* Bits to touch/compare */
u32 value; /* Value to check against/set */
}