GPIO subsystem and interrupts -- no way to do rising & falling edge on same pin?

I=E2=80=99m working on integrating the changes in kern/51676, but I seem =
to have stumbled into a glaring deficiency into how the GPIO subsystem =
supports interrupts.

Specifically, it does not seem like there is a way to trigger an =
interrupt on both the rising and falling edge of an event.  This is =
something that, for example, the Raspberry Pi=E2=80=99s SoC can do (and =
something I have use for in my application).  But alas, it seems as if =
the presence of GPIO_PIN_FALLING indicates falling, and the lack of it =
indicates rising.

Unfortunately, we=E2=80=99re nearly out of bits =E2=80=A6 there=E2=80=99s =
just one left, and so I=E2=80=99m hesitant to burn it to indicate both, =
especially since there are other capabilities that would be nice to =
expose (such as the Broadcom SoC=E2=80=99s non-sampled mode, although I =
don=E2=80=99t really need it immediately, myself).

Discuss.

-- thorpej