On Mon, 2022-08-15 at 17:47 -0700, Jakub Kicinski wrote:

On Mon, 15 Aug 2022 22:09:11 +0200 Johannes Berg wrote:

quoted

On Wed, 2022-08-10 at 19:23 -0700, Jakub Kicinski wrote:

quoted

+        attributes:
+          description: List of attributes in the space.
+          type: array
+          items:
+            type: object
+            required: [ name, type ]
+            additionalProperties: False
+            properties:
+              name:
+                type: string
+              type: &attr-type
+                enum: [ unused, flag, binary, u8, u16, u32, u64, s32, s64,
+                        nul-string, multi-attr, nest, array-nest, nest-type-value ]  

nest-type-value?

It's the incredibly inventive nesting format used in genetlink policy
dumps where the type of the sub-attr(s there are actually two levels)
carry a value (index of the policy and attribute) rather than denoting
a type :S :S :S

Hmm, OK, in the policy dump (not specific to genetlink, btw, can be used
for any policy, but is only generically hooked up for genetlink), we
have

[policy_idx] = {
  [attr_idx] = {
    [NL_POLICY_TYPE_ATTR_...] = ...
  }
}

Is that what you mean?

I guess I never really thought about this format much from a description
POV, no need to have a policy since you simply iterate (for_each_attr)
when reading it, and don't really need to care about the attribute
index, at least.

For future reference, how would you suggest to have done this instead?

quoted

quoted

+              description:
+                description: Documentation of the attribute.
+                type: string
+              type-value:
+                description: Name of the value extracted from the type of a nest-type-value attribute.
+                type: array
+                items:
+                  type: string
+              len:
+                oneOf: [ { type: string }, { type: integer }]
+              sub-type: *attr-type
+              nested-attributes:
+                description: Name of the space (sub-space) used inside the attribute.
+                type: string  

Maybe expand that description a bit, it's not really accurate for
"array-nest"?

Slightly guessing but I think I know what you mean -> the value of the
array is a nest with index as the type and then inside that is the
entry of the array with its attributes <- and that's where the space is
applied, not at the first nest level?

Right.

Right, I should probably put that in the docs rather than the schema,
array-nests are expected to strip one layer of nesting and put the
value taken from the type (:D) into an @idx member of the struct
representing the values of the array. Or at least that's what I do in
the C codegen.

Well mostly you're not supposed to care about the 'value'/'type', I
guess?

Not that any of these beautiful, precious formats should be encouraged
going forward. multi-attr all the way!

multi-attr?

quoted

Do you mean the "name of the enumeration" or the "name of the
enumeration constant"? (per C99 concepts) I'm a bit confused? I guess
you mean the "name of the enumeration constant" though I agree most
people probably don't know the names from C99 (I had to look them up too
for the sake of being precise here ...)

I meant the type. I think. When u32 carries values of an enum.
Enumeration constant for the attribute type is constructed from
it's name and the prefix/suffix kludge.

Indeed, I confused myself too ...

johannes