Re: [PATCH 0/2] hw/arm/npcm7xx_gpio: Add some pin state QOM

[Peter Maydell]

On Thu, 6 Apr 2023 at 01:25, Joe Komlodi <komlodi@google.com> wrote:
>
> Hi all,
>
> This series adds a couple QOM properties for retrieving and setting pin
> state via qom-get and qom-get.
>
> We ran into a situation in multi-SoC simulation where the BMC would need
> to update its input pin state based on behavior from the other SoC. It
> made the most sense to expose this over QMP, so this adds properties to
> allow people to do so.

This does leave the simulation in an odd situation if
the input GPIO was connected to some other device -- the
other device thinks it's put the GPIO line low, but then something
external has reached in and set it to 1, so the two ends of
what is conceptually a single signal line now disagree about
what voltage it's at...

It looks like the hw/gpio/aspeed_gpio device has been here before
you, only that device chose to use one bool property per GPIO
line. It would be nice to be consistent -- if we want to allow
QOM to set/get the GPIO line values, it should be the same
interface regardless of GPIO controller.

-- PMM