Re: [PATCH v2 5/8] gpu: nova-core: add NVKV decoder

["Eliot Courtney" <ecourtney@nvidia.com>]

On Thu Sep 10, 2026 at 4:47 PM JST, Alexandre Courbot wrote:
> On Thu Aug 27, 2026 at 11:12 PM JST, Eliot Courtney wrote:
> <...>
>> +    /// Decodes every pair into `schema` and returns the result of [`Schema::finish`].
>> +    pub(crate) fn decode<'s, S: Schema>(
>> +        &self,
>> +        schema: &'s mut S,
>> +    ) -> Result<impl Init<S::Target, Error> + 's> {
>> +        let mut cursor = Cursor::new(self.data);
>> +        while !cursor.is_empty() {
>> +            let op: Op = cursor.take_u64()?.into();
>> +
>> +            let key = op.key().into();
>> +            let index = op.index();
>> +            let op_value: u32 = op.value().into();
>> +            match op.opcode()? {
>> +                Opcode::Imm32 => {
>> +                    self.visit(schema, key, index, DecoderValue::Scalar32(op_value))?;
>> +                }
>> +                Opcode::Seq32 => {
>> +                    let values = cursor.take_u32s(num::u32_as_usize(op_value))?;
>> +                    for (i, &value) in values.iter().enumerate() {
>> +                        let key = Self::seq_key(key, i)?;
>> +                        self.visit(schema, key, index, DecoderValue::Scalar32(value))?;
>> +                    }
>> +                }
>> +                Opcode::Seq64 => {
>> +                    let values = cursor.take_u64s(num::u32_as_usize(op_value))?;
>> +                    for (i, &value) in values.iter().enumerate() {
>> +                        let key = Self::seq_key(key, i)?;
>> +                        self.visit(schema, key, index, DecoderValue::Scalar64(value))?;
>> +                    }
>> +                }
>
> Another thing that could be worth clarifying: are `Seq32`/`Seq64` with a
> count of `0` valid? Right now they won't trigger a visit or an error,
> i.e. they will be silently ignored. Whereas arrays of size 0 do trigger
> a visit (which sounds logical). I'm not saying this is a problem, just
> wondering if the behavior is consistent with what NVKV specifies in such
> cases.

Yes, it's valid to have a sequence of length zero according to the C
implementation [1]. The semantics are that a sequence of length 0 is
equivalent to nothing sent.

[1]: https://github.com/NVIDIA/open-gpu-kernel-modules/blob/615.71.09/src/nvidia/src/libraries/nvkv/nvkv.c#L62-L119