On Saturday 24 November 2007, Alan Cox wrote:
> >
> > What about for platforms where irq 0 is a valid irq?
>
> There are no such platforms. Linus made that absolutely clear every time
> this came up before
>
> 0 - No IRQ
>
> A platform with a physical or bus IRQ of 0 needs to remap it to a
> different constant.
However it's also common practice to use negative numbers to
flag "this is no IRQ" ... avoiding all confusions with zero.
- platform_get_irq(), platform_get_irq_byname() ... never
return zero, they return irq (positive) or errno
- PNP initializes invalid IRQs to "-1", and pnp_check_irq()
handles irq zero as in-range
- I'm sure I've seen negative numbers used elsewhere too
Something like
#define is_valid_irq(x) ((x) >= 0)
would work better than expecting sudden agreement everywhere
about a single number representing "this is not an IRQ".
- Dave
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
