Re: Using PXA arm board with MAX7319 GPIO expander input

[Eric Miao <eric.y.miao@gmail.com>]

On Tue, Feb 9, 2010 at 3:39 PM, Marc Zyngier <maz@misterjones.org> wrote:
> On Tue, 9 Feb 2010 09:05:22 +0800
> Eric Miao <eric.y.miao@gmail.com> wrote:
>
>> On Mon, Feb 8, 2010 at 8:32 PM, Marc Zyngier <maz@misterjones.org> wrote:
>> >> I just saw that there is indeed no support for irq line handling in this
>> >> driver. In order to use these lines as input for something like the
>> >> gpio_keys driver, support for that should be added. I never used this
>> >> driver and can't say whether it is under active development.
>> >
>> > It should be rather easy to introduce something similar to what I did for
>> > the pca953x driver (http://patchwork.kernel.org/patch/77418/)
>> >
>> > MAX732x seems a lot saner than PCA953x, as it has at least a hardware
>> > interrupt mask...
>>
>> Well, I'd say max732x is a chip of heavy simplification, input/output direction
>> of each pin is normally hardcoded, depending on the chip model used, there
>> seems no such interrupt mask registers for SW use really.
>
> I'm currently staring at the max7319 datasheet, and it really looks
> like there is such a register:
>
> "All input ports are continuously monitored for state changes
> (transition detection). Transitions are latched, allowing detection of
> transient changes. Any combination of inputs can be selected using the
> interrupt mask to assert the INT output. When the MAX7319 is
> subsequently accessed through the serial interface, any pending
> interrupt is cleared."
>
> So it would seems (although I agree with you that max732x as a GPIO
> expander is grossly simplified) that the feature is at least advertised.
>

That sounds like a good news. I'm seeing your previous implementation
of interrupt support on pca953x as a good one, so probably would be
good to follow that, and not sure Jebediah Huang can have this tested :-)