Hi, On 08/03/18 14:37, Rob Herring wrote: > On Thu, Mar 8, 2018 at 3:09 AM, Andre Przywara <andre.przywara@xxxxxxx> wrote: >> Hi, >> >> On 08/03/18 02:08, Rob Herring wrote: >>> On Wed, Mar 07, 2018 at 02:07:18AM +0000, Andre Przywara wrote: >>>> The PWM controllers found in the Allwinner A64, H5 and H6 SoCs are fully >>>> compatible to the PWM controllers found in the A13 and H3. >>> >>> If fully compatible, then shouldn't there be a fallback to one of the >>> existing compatible strings? >> >> Yes, that was the idea. I was already wondering how we would >> differentiate that from "real" compatible strings, but couldn't find >> convincing examples. So should that read: >> >> - compatible: should at least contain be one of: >> - "allwinner,sun4i-a10-pwm" >> - "allwinner,sun5i-a10s-pwm" >> - "allwinner,sun5i-a13-pwm" >> - "allwinner,sun7i-a20-pwm" >> - "allwinner,sun8i-h3-pwm" >> May in addition contain one of: >> - "allwinner,sun50i-a64-pwm" >> - "allwinner,sun50i-h5-pwm" >> - "allwinner,sun50i-h6-pwm" > > I can't validate a dts is correct with it written like this. Just list > each valid combination on each line: > > "allwinner,sun8i-h3-pwm", "allwinner,sun50i-h6-pwm" > > (Assuming "allwinner,sun50i-h6-pwm" was the first implementation and > h3 has the same block). Ah, OK, that's makes some sense. I didn't find too many examples outside of root compatible nodes in the binding docs, but I will use that. >> And this would possibly need to be amended once we need to actually use >> one of those strings (to implement a quirk, for instance)? > > The most specific compatible provides that. The driver matches on the > least specific one until you have a quirk to implement. Yeah, I was just wondering how a (non-Linux) driver author would induce what strings are actually needed just by reading the binding. But enumerating the combinations explicitly should solve this. Thanks! Andre. >> Or is there some other way of reserving those compatible strings, which >> are not expected to be matched in drivers directly? > > The binding should just list all that are appropriate from the start > and the driver is free to match on which ever string it wants. > > Rob > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
