Re: [PATCH net-next v4 6/7] docs: netlink: document struct support for genetlink-legacy

[Jakub Kicinski <kuba@kernel.org>]

On Fri, 24 Mar 2023 19:18:59 +0000 Donald Hunter wrote:
>  Legacy families can define C structures both to be used as the contents
> -of an attribute and as a fixed message header. The plan is to define
> -the structs in ``definitions`` and link the appropriate attrs.
> +of an attribute and as a fixed message header. Structs are defined
> +in ``definitions`` and referenced in operations or attributes.

We should call out that the structs in YAML are implicitly "packed"
(in the C sense of the word), so struct { u8 a; u16 b; u8 c; } is 
4 bytes not 6 bytes.

Any padding must be explicitly, C-like languages should infer the need
for explicit packing from whether the members are naturally aligned.

> +.. code-block:: yaml
> +
> +  definitions:
> +    -
> +      name: message-header
> +      type: struct
> +      members:
> +        -
> +          name: a
> +          type: u32
> +        -
> +          name: b
> +          type: string

Maybe not the most fortunate example :) cause I think that for
string/binary we'll need an explicit length. Maybe not for
last one if it's a flexible array... but that's rare in NL.

The rest LGTM, thanks!