On Wed, 2011-11-16 at 16:26 +0000, Rob Herring wrote: > On 11/16/2011 09:44 AM, Dave Martin wrote: > > On Fri, Nov 11, 2011 at 06:27:04PM +0000, Pawel Moll wrote: > >> This patch provides hooks for DT-based tile machine implementations > >> and adds Device Tree description for the motherboard. > >> > >> Signed-off-by: Pawel Moll <pawel.m...@arm.com> > >> --- > >> Documentation/devicetree/bindings/arm/vexpress | 92 ++++++++++ > >> arch/arm/boot/dts/vexpress-v2m-legacy.dtsi | 190 > >> +++++++++++++++++++++ > >> arch/arm/mach-vexpress/Kconfig | 4 + > >> arch/arm/mach-vexpress/core.h | 9 + > >> arch/arm/mach-vexpress/include/mach/motherboard.h | 8 + > >> arch/arm/mach-vexpress/v2m.c | 140 +++++++++++++++- > >> 6 files changed, 442 insertions(+), 1 deletions(-) > >> create mode 100644 Documentation/devicetree/bindings/arm/vexpress > >> create mode 100644 arch/arm/boot/dts/vexpress-v2m-legacy.dtsi > >> > >> diff --git a/Documentation/devicetree/bindings/arm/vexpress > >> b/Documentation/devicetree/bindings/arm/vexpress > > > > [...] > > > >> +Required properties in the root node: > >> +- compatible value: > >> + - for motherboard in "legacy" mode: > >> + compatible = "arm,vexpress-<model>", "arm,vexpress-legacy", > >> "arm-vexpress"; > >> + - for motherboard in "RS1" mode: > >> + compatible = "arm,vexpress-<model>", "arm-vexpress"; > > > > So, we have: > > > > arm,vexpress-* implies arm,vexpress > > arm,vexpress-* may imply arm,vexpress-legacy > > arm,vexpress-legacy implies arm,vexpress > > > > This means we have no bounded test for RS1-only features: > > the needed test is > > "compatible(node, "arm,vexpress") && !compatible(node, > > "arm,vexpress-legacy") > > > > Unfortunately, if there is someday an "rs2" memory map, that will also match > > the above. Using "inverse compatibility" in this way feels dangerous, > > because the condition will pass for an arbitrary set of future conditions > > that we haven't imagined yet. > > > > This means it's, impossible even in principle to panic the kernel cleanly if > > presented with a device tree for a platform variant which is too new for the > > kernel to support. > > > > > > Can we instead have a specific "arm,vexpress-rs1"? > > > > compatible = "arm,vexpress-<model>", "arm-vexpress-rs1", "arm-vexpress"; > > > > Then, we can be exact about compatibility: universal features are compatible > > with "arm,vexpress"; memory-map-specific features are compatible with either > > "arm,vexpress-legacy" or "arm,vexpress-rs1". > > Really, legacy is a bad name.
http://en.wikipedia.org/wiki/De_gustibus_non_est_disputandum ;-) This is de-facto name we use in ARM. See: http://infocenter.arm.com/help/topic/com.arm.doc.dui0447e/ch04s02s01.html > If you defined the property when the > original vexpress was designed, it never would have had legacy in the > name. Generally speaking you never change bindings on old platforms. > > So I would have "arm,vexpress" mean legacy and "arm,vexpress-rs1" be the > new memory map. I'd rather second Dave's idea of having > > compatible = "arm,vexpress-<model>", "arm-vexpress-rs1", "arm-vexpress"; and >> + compatible = "arm,vexpress-<model>", "arm,vexpress-legacy", >> "arm-vexpress"; Cheers! Paweł _______________________________________________ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss
