Re: [PATCH 3/3] gpio: mcp23s08: Add option to configure IRQ as active high

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Thu, Nov 27, 2014 at 3:36 PM, Alexander Stein
<alexander.stein@xxxxxxxxxxxxxxxxxxxxx> wrote:
> On Thursday 27 November 2014 14:58:39, Linus Walleij wrote:

>> Sorry too confused by this, can you explain?
>
> Sure. Until now ODR is cleared as reset default while INTPOL explicitly gets cleared.
> So the INT output pin on the MCP23S17 is an active-low output pin which will trigger
> an active-low interrupt.

OK... I thought it was some kind of input line to the device. Now I get it, it
is what is generated *out* of this device. Please state this in the bindings.

> While this is useually great, as most interrupt pins are active low, our board design
> requires an active-high output.

OK I get it :)

> You might wonder why I then also changed IRQF_TRIGGER_LOW to
> IRQF_TRIGGER_HIGH for my board the interrupt line is actually active low.
> This is due the fact that GIC only supports active high-interrupts (any other flag
> results in request fail) but the microcontroller has a feature to inverse these interrupt triggers.

Very convoluted, but common in electronics, OK, no problem.

Yours,
Linus Walleij
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