Re: Adding an interrupt locator to the GPIO, I2C and SPI buses

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Apr 19, 2013 at 09:42:37PM +0200, Pierre Pronchery wrote:
> >>> That would be a problem if the GPIO module has less interrupt lines than
> >>> interrupt sources (as in the AM335x: 32 GPIO per module but only 2
> >>> interrupt lines to the PIC):
> >>
> >> Tell me if I'm wrong, but I don't think you understood what's happening 
> >> here: the GPIO interrupt range that I described on OMAP is virtual. 
> >> Therefore, gpio_to_irq() would return a virtual interruption number.
> > 
> > But the interrupt framework doesn't know about "virtual interruption 
> > number".
> > Only the gpio driver knows it. So you can't use intr_establish() (which
> > is from the interrupt framework, not the gpio driver) with it.
> 
> As a matter of fact it doesn't have to. I can use intr_establish(),
> because I am doing it and it works already (even without the patch I
> attached earlier here). Just look at my original e-mail in this thread
> (first paragraph + example).
> 
> >> The underlying GPIO bus driver would be in charge to determine which pin 
> >> really triggered the interrupt, and tell the corresponding driver. The 
> >> OMAP GPIO driver does exactly this already.
> > 
> > Yes, of course. So the interrupt framework calls the GPIO interrupt handler,
> > which calls the driver's handler. It's the GPIO driver which has to know
> > the driver's interrupt handler, not the interrupt framework.
> > So the driver has to register its interrupt handler to the GPIO driver,
> > not to the interrupt framework.
> 
> Consider this:
> int gpio_to_irq(void * gpio, int pin);
> 
> The GPIO _device_ driver wants to know which virtual interrupt
> corresponds to a given pin. It calls gpio_to_irq() with ga_gpio as
> obtained from "struct gpio_attach_args". This call reaches the GPIO
> _bus_ driver, which:
> - knows its own actual interrupt number, but we don't care;
> - knows its interrupt range reference, which it registered to the
>   underlying interrupt multiplexer, and adds to "pin" and returns.

What is the "interrupt multiplexer" ? Where can I find it ?
And I couldn't find a gpio_to_irq() function in the source
(neither in arm code, nor in MI code).

On the other hand, I could find a omap_gpio_intr_establish(), which
is used by another driver. It doens't use a "virtual interrupt", but
a gpio pin.

Maybe I missed something in the arm code. I know better the x86 or mips
ports, and I'm sure that this "interrupt multiplexer" concept is not
implemented here.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--