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Date: Wed, 21 Nov 2012 11:14:30 -0700
From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Grant Likely <grant.likely@secretlab.ca>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rob Herring <rob.herring@calxeda.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        devicetree-discuss <devicetree-discuss@lists.ozlabs.org>
Subject: Re: [PATCH] of: Have of_device_add call platform_device_add rather
 than device_add
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On Wed, Nov 21, 2012 at 06:07:46PM +0000, Grant Likely wrote:

> > Which is nesting the generic gpio driver under a larger region..
> 
> Try two sibling nodes with overlapping addresses. There are powerpc
> device trees doing that even though it isn't legal by the ofw and
> epapr specs.

Both my examples were using sibling nodes in the OF tree.

	pex@e0000000 {
		device_type = "pci";
		ranges = <0x02000000 0x00000000 0x00000000  0xe0000000  0x0 0x8000000>;
		bus-range = <0x0 0xFF>;
		chip@0 {
			ranges = <0x02000000 0x00000000 0x00000000  0x02000000 0x00000000 0x00000000  0x0 0x8000000>;
			chip_control@0 {
				compatible = "orc,chip,control";
				assigned-addresses = <0x02000000 0x0 0x0  0x0 4096>;
			};

			gpio3: chip_gpio@8 {
			        #gpio-cells = <2>;
				compatible = "linux,basic-mmio-gpio";
				gpio-controller;
				reg-names = "dat", "set", "dirin";
				assigned-addresses = <0x02000000 0x0 0x8  0x0 4>,
				                     <0x02000000 0x0 0xc  0x0 4>,
				                     <0x02000000 0x0 0x10  0x0 4>;
			};

Non-conformant yes, but it is the simplest way to get linux to bind
two drivers to the same memory space.

Jason