Date:   Tue, 3 Oct 2017 08:18:33 -0500
From:   Rob Herring <robherring2@...il.com>
To:     Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Grant Likely <grant.likely@...retlab.ca>,
        David Gibson <david@...son.dropbear.id.au>,
        Tom Rini <trini@...sulko.com>,
        Franklin S Cooper Jr <fcooper@...com>,
        Matt Porter <mporter@...sulko.com>,
        Simon Glass <sjg@...omium.org>,
        Phil Elwell <philip.j.elwell@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Marek Vasut <marex@...x.de>,
        Devicetree Compiler <devicetree-compiler@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] yamldt v0.5, now a DTS compiler too

On Mon, Oct 2, 2017 at 2:46 PM, Pantelis Antoniou
<pantelis.antoniou@...sulko.com> wrote:
> Hi Rob,
>
> On Sun, 2017-10-01 at 17:00 -0500, Rob Herring wrote:
>> On Thu, Sep 28, 2017 at 2:58 PM, Pantelis Antoniou
>> <pantelis.antoniou@...sulko.com> wrote:
>> > Hello again,
>> >
>> > Significant progress has been made on yamldt and is now capable of
>> > not only generating yaml from DTS source but also compiling DTS sources
>> > and being almost fully compatible with DTC.
>>
>> Can you quantify "almost"?
>>
>> > Compiling the kernel's DTBs using yamldt is as simple as using a
>> > DTC=yamldt.
>>
>> Good.
>>
>> >
>> > Error reporting is accurate and validation against a YAML based schema
>> > works as well. In a short while I will begin posting patches with
>> > fixes on bindings and DTS files in the kernel.
>>
>> What I would like to see is the schema format posted for review.
>>
>
> I'm including the skeleton.yaml binding which is the template for
> the bindings and a board-example.yaml binding for a top level binding.
>
>> I would also like to see the bindings for top-level compatible strings
>> (aka boards) as an example. That's something that's simple enough that
>> I'd think we could agree on a format and start moving towards defining
>> board bindings that way.
>>
>
> Note there is some line wrapping I'm including a link
> to the github repo of the files:
>
>
> The skeleton.yaml
>
> https://raw.githubusercontent.com/pantoniou/yamldt/master/validate/bindings/skeleton.yaml
>
> %YAML 1.1
> ---
> # The name of the binding is first
> # The anchor is put there for use by others
> skeleton: &skeleton

This and "id" seem redundant.

>   version: 1
>
>   id: skel-device
>
>   title: >
>     Skeleton Device
>
>   maintainer:
>     name: Skeleton Person <skel@...nel.org>
>
>   description: >
>     The Skeleton Device binding represents the SK11 device produced by
>     the Skeleton Corporation. The binding can also support compatible
>     clones made by second source vendors.
>
>   # The class is an optional property that declares this
>   # binding as part of a larger set
>   # Multiple definitions are possible
>   class: [ device, spi-device ]
>
>   # This binding inherits property characteristics from the generic
>   # spi-slave binding
>   # Note that the notation is standard yaml reference
>   inherits: *spi-slave
>
>   # virtual bindings do not generate checkers
>   virtual: true

virtual is an overloaded term.

>
>   # each property is defined by each name
>   properties:
>
>     # The compatible property is a reserved name. The type is always
> "string"
>     # and should not be repeated device binding.
>     compatible:
>       category: required        # required property
>       type: strseq              # is a sequence of strings
>
>       description: >
>         FX11 is a clone of the original SK11 device
>
>       # v is always the name of the value of the property
>       # np is passed to the checker and is the current
>       # node pointer. We can access properties and call
>       # methods that operate on them.
>       # There can be multiple constraints, just put them
>       # into a sequence.
>       # Note that the BASE("skel,sk11") form from the previous
>       # binding will have to be reworked.
>       constraint: |
>         anystreq(v, "skel,sk11") ||
>         anystreq(v, "faux,fx11")

Constraints and logic ops were certainly not decided in the last
attempt and I think will be the hardest part to define. I see you are
using eBPF in the checker. Is that where anystreq comes from?

How would you express the ordering requirement (most significant
compatible first)?

>
>     # The reg property is a reserved name. The type is always "int" and
>     # should not be repeated in a device binding. Constraints are
> defined
>     # only in the context of the parent node's address, size, and ranges
>     # cells. The description is inherited from the spi-slave binding.
>     # Note that if inheriting from a base binding this declaration may
>     # be omitted.
>     reg:
>       category: required        # required property
>       type: intseq              # is a sequence of integers
>
>     # spi-max-frequency needs the device-specific constraint to be
> supplied
>     spi-max-frequency:
>       # this constraint is dependent on the compatible property
>       # property containing "skel,sk11"
>       constraint: |
>         v <= anystreq(get_strseq(np, "compatible"), "skel,sk11") ?
> 10000000 : 1000000
>
>     # This property overrides the generic binding description with
>     # a device specific description in order to mention the chip's
>     # h/w cfg strapping pins.
>     spi-cs-high:
>       description: >
>         Set if skeleton device configuration pins are set for chip
>         select polarity high
>
>     # Device specific properties don't inherit characteristic from a
> generic
>     # binding so category, type, constraint, and description must be
> specified
>     # if needed.
>     skel,deprecated1:
>       # note that the category may be declare more than one option
>       category: [ deprecated, optional ]
>       type: int
>       constraint: |
>         v >= 100000 && v <= 200000
>       description: >
>         First of two deprecated properties.
>
>     # There are no constraints for properties of empty type
>     skel,deprecated2:
>       category: deprecated
>       type: empty
>       description: >
>         Second of two deprecated properties.
>
>     # This example could be auto-generated rather than explicitly
> included
>     # in the yaml source.
>     # Note that the YAML example must be validated against this binding
>     # to be an accepted entry
>     example:
>
>       dts: |
>         sk11@0 {
>             compatible = "skel,sk11";
>             reg = <0>;
>             spi-max-frequency = <1000000>;
>             spi-cs-high;
>         };
>
>       yaml: |
>         sk11@0:
>           compatible: "skel,sk11"
>           reg: 0
>           sip-max-frequency: 1000000
>           spi-cs-high: true
>         ---
> ...
>
> And board-example.yaml
>
> https://raw.githubusercontent.com/pantoniou/yamldt/master/validate/bindings/board-example.yaml
>
> %YAML 1.1
> ---
> board-example: &board-example
>   version: 1
>
>   title: A board example using compatible and model properties
>
>   maintainer:
>     name: Skeleton Person <skel@...nel.org>
>
>   class: board
>
>   # this binding is selected when the compatible property constraint
> matches
>   selected: "compatible"

We need some way to express this must be the root node. More
generally, we need to express what bindings must be a child of (think
sub-devices in MFDs). Perhaps that's just a "parent" key with the
value being the id/name.

>
>   description: >
>     A board binding example. Matches on a top-level compatible string
> and model.
>
>   properties:
>
>     compatible:
>       category: required
>       type: strseq
>       description: |
>         Compatible strings for the board example.
>         The depth of the node must be zero, i.e. root.
>
>       constraint: |
>         get_depth(np) == 0 && (

Ahh, I guess this is how you are doing it. I don't think this works
for any value other than 0. An MFD could be at any level.

>         anystreq(v, "example,evm") ||
>         anystreq(v, "example,evm2") ||
>         anystreq(v, "example,base"))
>
>     model:
>       category: required
>       type: str
>       description: models that this board family supports
>       constraint: |
>         streq(v, "Example EVM") ||
>         streq(v, "Example EVM2")
>
>   example:
>     dts: |
>       / {
>           compatible = "example,evm", "example,base";
>           model = "Example EVM";
>       };
>     yaml: |
>       compatible: [ "example,evm", "example,base" ] ;
>       model: "Example EVM";

I really don't want to see 2 examples. For now, it's going to be dts
format. It could be converted by script later if needed.

Overall, I think this format is a bit long for boards. We have
something like ~1000 boards in arch/arm last I checked. I want adding
a board binding to be very short and easy to review. It's often only a
1 line change. The main issue I have is it is just each SoC (or SoC
family) does things their own way.

> As you see it's almost identical to what you've originally posted.

I barely remember and no one ever commented on it.

Rob

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