pca9539 I2C gpio expander

[Steven A. Falco]

I am attempting to use a pca9539 I2C gpio driver on a PPC440EPx board.  The
driver is "drivers/gpio/pca953x.c".  I've added an entry to the .dts file:

IIC0: i2c at ef600700 {
	compatible = "ibm,iic-440epx", "ibm,iic";
	...
	pca9539 at 76 {
		compatible = "ti,pca9539";
		reg = <76>;
	};
};

of_register_i2c_devices sees this entry and calls i2c_new_device.
i2c_new_device copies info->platform_data to client->dev.platform_data, but
I think that this structure is empty (at least I don't see where
of_register_i2c_devices would set it).

pca953x_probe is eventually called, but it expects to find its "lowest gpio
number" in client->dev.platform_data->gpio_base, which has not been set.  So
pca953x_probe returns -ENODEV.

I don't understand where the disconnect is.  Should I be able to use the
pca953x.c driver, or is it somehow incompatible?

If it is incompatible, is there a strategy for making it compatible?

	Steve