How to register GPIOs over PCI

[Schwarz,Andre]

Grant, Anton,

reading through the of/gpio docs and thinking about some improvements for our
proprietary "ancient" code gives a lot of opportunities for major improvements
... since you are authors and your quick help in the past is really appreciated
I dare to address you directly ;-)

On some (mostly PowerPC) based boards we have NAND-Flash connected to a PCI
FPGA.
There's no NAND controller inside ... just bitbang. Currently there's an
implementation using "struct nand_chip" + hooks + nand_scan() inside the pci
driver. Since the driver is designed to do other things and is not available
during boot (=no RFS on Nand) I definitely want to get rid of this.

To me it looks like we could use the "gpio-nand" driver. All we need is
registering the proper (mem mapped) GPIOs with the required names via
device-tree. As far as I understand the FPGA can be considered an
of_mm_gpio_chip ?

Honestly I don't know how to define it using dts syntax.

All we have regarding PCI is general bus ranges, devsel and irq lines ... and of
course the offset inside the FPGA.
I've not seen a direct representation of a PCI device - only SoC components.

How am I supposed to handle the unknown (=dynamically assigned) base address ?
Since the system also has PCI slots I can't make sure to always get the same
adress ...


Can you give some hints/advice how to define the FPGA as a GPIO-Controller ?


Regards,
André

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