On Thu, Nov 27, 2014 at 3:36 PM, Alexander Stein
[off-list ref] wrote:

On Thursday 27 November 2014 14:58:39, Linus Walleij wrote:

quoted

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