Re: DT schemas for multi-transport bindings

[Rob Herring <robh@kernel.org>]

On Fri, Oct 25, 2019 at 01:43:33PM -0700, Dmitry Torokhov wrote:
> Hi Rob,
> 
> I am trying to wrap my mind around converting multi-transport bindings
> (let's say TSC2004/5 controller which is pretty much the same part, but
> one is I2C while another is SPI interface). There is a set of common
> properties, and then we can have transport-specific ones (for example,
> spi-max-frequency for SPI case). 

I'm pretty sure we already have some examples of this.

You could have 3 files with common props, i2c props, and spi props, but 
that's probably an overkill. I'd just list all the possible properties 
in one file and then they can be made conditional as needed.

For bus properties you really only need to list them if required or you 
have additional constraints.

> Is it possible to annotate that some
> properties are only needed for certain compatible, similarly to how
> patternProperties work (but instead of matching node name we'd match on
> compatible)?

Yes, with if/then schema. There's numerous examples of this. It's a 
little more verbose than I'd like, but that's because generally each 
property schema is independent.


> Also, from syntax POV, how do I reference file ooutside of current
> directory? I.e. how do I reference .../spi/spi-controller.yaml from
> .../input/touchscreen/tsc2005.yaml?

You don't. TSC2005 is not a SPI controller/master. Every SPI controller 
should reference spi-controller.yaml and that defines the bus structure 
and allowed SPI bus properties in child nodes.

If you did though, it would be '../spi/spi-controller.yaml'

Rob