[Skiboot] [PATCH 1/2] include: Add PRD message definition

[Stewart Smith]

Jeremy Kerr <jk at ozlabs.org> writes:

> Hi Stewart,
>
>>>> +struct opal_prd_msg {
>>>> +	uint8_t		type;
>>>> +	uint8_t		pad[3];
>>>> +	uint32_t	token;
>>>
>>> Do we want a version in here?
>>>
>>> I'm thinking of future when we have either:
>>> a) more types
>>> b) some types have extended information.
>>>
>>> Please clearly document how OS should behave in the event of unknown
>>> types or newer version.
>> 
>> We just make a new message in that case, though we could use pad as
>> flags ...
>
> We have a version field in the init message; this'll  be the first
> message that the "client" sends.

Ahh, excellent! So in the event of bumping the version, it's the initial
handshake that works out the versions of messages back and forth. We
probably want to document that so I don't ask the same question next
time :)

(and after I've trained everyone to ask all the questions for each
opal.h patch :)

>>> seeing as this is an opal_msg, can we also have a BUILD_ASSERT() of it
>>> being < sizeof(struct opal_msg) ?
>> 
>> Ack.
>
> Already have one in the new version of 2/2 :)
>
> This change also uses the __be32/__be64 types, for endian annotation.

Excellent!