On Mon, Dec 05, 2011 at 07:35:16AM -0600, Rob Herring wrote:
> Shawn,
>
> On 12/05/2011 12:55 AM, Shawn Guo wrote:
> > On Wed, Nov 30, 2011 at 05:45:36PM -0700, Stephen Warren wrote:
> > [...]
> >> static void tegra_gpio_irq_ack(struct irq_data *d)
> >> {
> >> - int gpio = d->irq - INT_GPIO_BASE;
> >> + int gpio = d->hwirq;
> >>
> > Though it's working right now, I'm not sure it's safe enough. This
> > only works when d->hwirq_base is 0, which is true for now. But I doubt
> > it will be always true. I guess hwirq_base was introduced there for
> > some reason. When some day irqdomain starts using this field, the
> > above code starts being broken. IMO, the way that generic-chip.c is
> > using to calculate the number, d->irq - gc->irq_base, is much more
> > safer.
>
> It does work as the GIC hwirq_base is non-zero. It was introduced
> exactly so that no conversion of hwirq is needed for functions like
> this. hwirq_base is the starting point local to the controller
> numbering. Say you have gpio controller with 16 lines, but only the
> upper 8 lines have interrupt capability. Then you would set hwirq_base
> to 8 and nr_irq to 8. Then hwirq will always be set to 8-15.
>
Ah, ok. In that case, it's safe to use. Thanks for help understand
it. I will use hwirq for my gpio-mxc patch then.
--
Regards,
Shawn
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