Re: [PATCH 07/10] riscv: add ISA extension parsing for Zcmop

Clément Léger
2024-04-16T15:24:06Z

On 16/04/2024 16:54, Conor Dooley wrote:
> On Mon, Apr 15, 2024 at 11:10:24AM +0200, Clément Léger wrote:
>>
>>
>> On 11/04/2024 13:53, Conor Dooley wrote:
>>> On Thu, Apr 11, 2024 at 11:08:21AM +0200, Clément Léger wrote:
>>>>>> If we consider to have potentially broken isa string (ie extensions
>>>>>> dependencies not correctly handled), then we'll need some way to
>>>>>> validate this within the kernel.
>>>>>
>>>>> No, the DT passed to the kernel should be correct and we by and large we
>>>>> should not have to do validation of it. What I meant above was writing
>>>>> the binding so that something invalid will not pass dtbs_check.
>>>>
>>>> Acked, I was mainly answering Deepak question about dependencies wrt to
>>>> using __RISCV_ISA_EXT_SUPERSET() which does not seems to be relevant
>>>> since we expect a correct isa string to be passed.
>>>
>>> Ahh, okay.
>>>
>>>> But as you stated, DT
>>>> validation clearly make sense. I think a lot of extensions strings would
>>>> benefit such support (All the Zv* depends on V, etc).
>>>
>>> I think it is actually as simple something like this, which makes it
>>> invalid to have "d" without "f":
>>>
>>> | diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
>>> | index 468c646247aa..594828700cbe 100644
>>> | --- a/Documentation/devicetree/bindings/riscv/extensions.yaml
>>> | +++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
>>> | @@ -484,5 +484,20 @@ properties:
>>> | Registers in the AX45MP datasheet.
>>> | https://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf
>>> |
>>> | +allOf:
>>> | + - if:
>>> | + properties:
>>> | + riscv,isa-extensions:
>>> | + contains:
>>> | + const: "d"
>>> | + not:
>>> | + contains:
>>> | + const: "f"
>>> | + then:
>>> | + properties:
>>> | + riscv,isa-extensions:
>>> | + false
>>> | +
>>> | +
>>> | additionalProperties: true
>>> | ...
>>>
>>> If you do have d without f, the checker will say:
>>> cpu@2: riscv,isa-extensions: False schema does not allow ['i', 'm', 'a', 'd', 'c']
>>>
>>> At least that's readable, even though not clear about what to do. I wish
>>
>> That looks really readable indeed but the messages that result from
>> errors are not so informative.
>>
>> It tried playing with various constructs and found this one to yield a
>> comprehensive message:
>>
>> +allOf:
>> + - if:
>> + properties:
>> + riscv,isa-extensions:
>> + contains:
>> + const: zcf
>> + not:
>> + contains:
>> + const: zca
>> + then:
>> + properties:
>> + riscv,isa-extensions:
>> + items:
>> + anyOf:
>> + - const: zca
>>
>> arch/riscv/boot/dts/allwinner/sun20i-d1-dongshan-nezha-stu.dtb: cpu@0:
>> riscv,isa-extensions:10: 'anyOf' conditional failed, one must be fixed:
>> 'zca' was expected
>> from schema $id: http://devicetree.org/schemas/riscv/extensions.yaml
>>
>> Even though dt-bindings-check passed, not sure if this is totally a
>> valid construct though...
>
> I asked Rob about this yesterday, he suggested adding:
> riscv,isa-extensions:
> if:
> contains:
> const: zcf
> then:
> contains:
> const: zca

That is way more readable and concise !

> to the existing property, not in an allOf. I think that is by far the
> most readable version in terms of what goes into the binding. The output
> would look like:
> cpu@0: riscv,isa-extensions: ['i', 'm', 'a', 'd', 'c'] does not contain items matching the given schema
> (for d requiring f cos I am lazy)

Than fine by me. The error is at least a bit more understandable than
the one with the false schema ;)

>
> Also, his comment about your one that gives the nice message was that it
> would wrong as the anyOf was pointless and it says all items must be
> "zca".

That's what I understood also.

> I didn't try it, but I have a feeling your nice output will be
> rather less nice if several different deps are unmet - but hey, probably
> will still be better than having an undocumented extension!
>

If you are ok with that, let's go with Rob suggestion. I'll resubmit a
V2 with validation for these extensions and probably a followup for the
other ones lacking dependency checking.

Thanks,

Clément