On Fri, Jan 18, 2013 at 01:40:00AM +0000, Grant Likely wrote:

This allows platform_device_add a chance to call insert_resource on all
of the resources from OF. At a minimum this fills in proc/iomem and
presumably makes resource tracking and conflict detection work better.
However, it has the side effect of moving all OF generated platform
devices from /sys/devices to /sys/devices/platform/. It /shouldn't/
break userspace because userspace is not supposed to depend on the full
path (because userspace always does what it is supposed to, right?).

This may cause breakage if either:
1) any two nodes in a given device tree have overlapping & staggered
   regions (ie. 0x80..0xbf and 0xa0..0xdf; where one is not contained
   within the other). In this case one of the devices will fail to
   register and an exception will be needed in platform_device_add() to
   complain but not fail.

Grant,

The patch introduce a regression on imx6q boot.  The IOMUXC block on
imx6q is special.  It acts not only a pin controller but also a system
controller with a bunch of system level registers in there.  That's why
we currently have the following two nodes in imx6q device tree with the
same start "reg" address, which work with drivers/mfd/syscon.c and
drivers/pinctrl/pinctrl-imx6q.c respectively.

	gpr: iomuxc-gpr at 020e0000 {
		compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
		reg = <0x020e0000 0x38>;
	};

	iomuxc: iomuxc at 020e0000 {
		compatible = "fsl,imx6q-iomuxc";
		reg = <0x020e0000 0x4000>;
	};

With the patch in place, pinctrl-imx6q fails to register like below.

syscon 20e0000.iomuxc: syscon regmap start 0x20e0000 end 0x20e3fff registered
imx6q-pinctrl 20e0000.iomuxc: can't request region for resource [mem 0x020e0000-0x020e3fff]
imx6q-pinctrl: probe of 20e0000.iomuxc failed with error -16

Shawn

2) any device calls request_mem_region() on a region larger than
   specified in the device tree. In this case the device node may be
   wrong, or the driver is overreaching. In either case I'd like to know
   about any problems and fix them.