Re: [libvirt] [RFC v4 00/13] qmp: query-device-slots command
On Tue, Aug 15, 2017 at 01:57:50PM -0500, Eric Blake wrote:
On 08/14/2017 04:57 PM, Eduardo Habkost wrote:
> Changelog
> ---------
>
> Changes v3 -> v4:
> * New compact representation of slot sets.
> * New generic code to automatically merge similar slots
> into a single entry in the command output while keeping
> implementations of the method simpler.
> * Example implementation of IDE and USB bus enumeration
>
> Slot sets are represented by a list of option names and sets of
> possible values for each of those options. The command uses a
> compact representation for the set of valid values for an option.
> For example, the following set of 5 PCI functions:
>
> bus: pcie.0
> device-number: 31
> functions: 1,4,5,6,7
>
> would be represented in the JSON data as:
>
> {"available":false,"count":5,
>
"device-types":["pci-device"],"hotpluggable":false,
> "opts":[
> {"option":"function","values":[1,[4,7]]},
A list (and not just a single-type list, but a list that mixes scalar
and sublist),
> {"option":"device-number","values":31},
vs. a scalar. Why not a one-element array?
It was just to keep the representation as compact as possible, in
the common case of single-value sets. Probably we can drop that
feature as it saves only 2 bytes in the JSON representation.
> {"option":"bus","values":"pcie.0"}],
> "opts-complete":true}
>
> I planned to use QAPI alternates to model/document that in the
> schema, but it would require implementing a few missing features
> in QAPI alternate support.
Yeah, I can see how existing QAPI alternates do not yet support arrays,
which becomes important to your representation. Do you need help
getting the QAPI generator improved to support a particular feature that
you found to be lacking?
I think the lack of support for lists on alternates was the main
obstacle.
Probably we would also need to remove the restriction against
alternates with ambiguous string representations, to allow a
list/number/string/bool alternate to be defined.
Being able to set constraints on the number of elements of a list
would be nice to have, but not required.
--
Eduardo