Advice on using gpio-brcmstb with gpio-ranges

[Phil Elwell <phil@xxxxxxxxxxxxxxx>]

Hello,

I'm having difficulty using the gpio-brcmstb driver with the
gpio-ranges property. gpio-brcmstb allows multiple banks of up to 32
GPIO lines to be declared using a single DT node. However, if you do
that, any declared gpio-ranges get applied to all banks without any
kind of filtering or adjustment. This is because the gpio-brcmstb
makes use of gpio-mmio, which requires one gpio_chip per bank. These
gpio_chips have the same DT node, hence the same ranges, but are
unaware that only a subset applies to them.

The GPIO<->pinctrl mapping can be configured in driver code, but this
is deprecated (as is forcing global GPIO base numbers to start at
zero, but the driver does it anyway).

What is the best way forward? Does one have to say that in
gpio-brcmstb, gpio-ranges and multiple banks are mutually
incompatible?

Thanks,

Phil