On Wednesday 24 October 2012 12:54:05 Alan Stern wrote: > On Wed, 24 Oct 2012, Stephen Warren wrote: > > > Device tree files always need a completely specific value in the > > compatible property, even when less-specific/more-generic values are > > also present. So for example, the Linux driver might only care about the > > following existing: > > > > compatible = "usb-ehci". > > > > However, any actual EHCI controller is always some specific model, so > > the compatible value must define which specific model it is, e.g.: > > > > compatible = "nvidia,tegra20-ehci", "usb-ehci". > > > > Now lets say the Tegra30 EHCI controller is identical to the Tegra20 > > controller. That needs to be explicitly represented too: > > > > compatible = "nvidia,tegra30-ehci", "nvidia,tegra20-ehci", "usb-ehci". > > > > In that case, the driver might still only declare support for > > "nvidia,tegra20-ehci", but "nvidia,tegra30-ehci" is added to be explicit > > about the actual HW model. > > > > This doesn't continue forever though; you typically only list the > > specific HW model, the base specific model it's compatible with, and any > > generic value needed. So, a hypothetical Tegra40 EHCI controller would be: > > > > compatible = "nvidia,tegra40-ehci", "nvidia,tegra20-ehci", "usb-ehci". > > > > Given that, there is always something to key any newly required quirk > > off, so even if the need for a quirk is found later, the device tree > > already contains the information needed to trigger it. > > Okay. It appears that quite a few .dts/.dtsi files mention "usb-ehci", > for no apparent reason (given that the drivers don't list it): > > [stern@iolanthe usb-3.6]$ find arch -name '*.dts*' | xargs grep usb-ehci > arch/mips/cavium-octeon/octeon_3xxx.dts: compatible = "cavium,octeon-6335-ehci","usb-ehci"; > arch/mips/cavium-octeon/octeon_68xx.dts: compatible = "cavium,octeon-6335-ehci","usb-ehci"; > arch/arm/boot/dts/tegra20.dtsi: compatible = "nvidia,tegra20-ehci", "usb-ehci"; > arch/arm/boot/dts/tegra20.dtsi: compatible = "nvidia,tegra20-ehci", "usb-ehci"; > arch/arm/boot/dts/tegra20.dtsi: compatible = "nvidia,tegra20-ehci", "usb-ehci"; > arch/arm/boot/dts/at91sam9x5.dtsi: compatible = "atmel,at91sam9g45-ehci", "usb-ehci"; > arch/arm/boot/dts/spear13xx.dtsi: compatible = "st,spear600-ehci", "usb-ehci"; > arch/arm/boot/dts/spear13xx.dtsi: compatible = "st,spear600-ehci", "usb-ehci"; > arch/arm/boot/dts/spear3xx.dtsi: compatible = "st,spear600-ehci", "usb-ehci"; > arch/arm/boot/dts/spear600.dtsi: compatible = "st,spear600-ehci", "usb-ehci"; > arch/arm/boot/dts/spear600.dtsi: compatible = "st,spear600-ehci", "usb-ehci"; > arch/arm/boot/dts/at91sam9g45.dtsi: compatible = "atmel,at91sam9g45-ehci", "usb-ehci"; > arch/powerpc/boot/dts/wii.dts: compatible = "nintendo,hollywood-usb-ehci", > arch/powerpc/boot/dts/wii.dts: "usb-ehci"; > arch/powerpc/boot/dts/sequoia.dts: compatible = "ibm,usb-ehci-440epx", "usb-ehci"; > arch/powerpc/boot/dts/canyonlands.dts: compatible = "ibm,usb-ehci-460ex", "usb-ehci"; > > Is there a real reason that I'm not aware of? Or can all these entries > safely be removed? Apart from the powerpc entries for which a real driver exists, the others were probably added in the hope that sooner or later, someone will come up with a matching driver, and the corresponding dts file would not even have to be updated to benefit from this. -- Florian -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
