Re: [RFC] Dummy GPIO driver for use with SPI

On Fri, Dec 12, 2008 at 09:22:02AM -0500, Steven A. Falco wrote:

This patch adds a dummy GPIO driver, which is useful for SPI devices
that do not have a physical chip select.

Signed-off-by: Steven A. Falco <redacted>
---
The SPI subsystem requires a chip-select for each connected slave
device.  I have a custom board with an Atmel "co-processor".  This part
is reprogrammed via SPI, so it needs a chip select to satisfy the SPI
subsystem, but my hardware does not have a physical CS connected.

I could waste a "no-connect" GPIO pin, but I'd rather not.  So, I've
written a dummy GPIO driver, which behaves exactly like a real GPIO
device, but with no underlying hardware.  This could also be useful
as a template for real GPIO drivers.

I use the following dts entry:

	GPIO3: dummy@ef500000 {
		compatible = "linux,dummy-gpio";
		reg = <ef500000 1>;
		gpio-controller;
		#gpio-cells = <2>;
	};

This is not sane.  I can see reasons it might be useful to have a
dummy gpio driver within the kernel, but since this doesn't represent
any real hardware, it should not appear in the device tree.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson