Re: [PATCH 00/18] qapi/qom: QAPIfy object-add
On 30/11/20 13:25, Kevin Wolf wrote:
This series adds a QAPI type for the properties of all user
creatable
QOM types and finally makes QMP object-add use the new ObjectOptions
union so that QAPI introspection can be used for user creatable objects.
After this series, there is least one obvious next step that needs to be
done: Change HMP and all of the command line parser to use
ObjectOptions, too, so that the QAPI schema is consistently enforced in
all external interfaces. I am planning to send another series to address
this.
In a third step, we can try to start deduplicating and integrating things
better between QAPI and the QOM implementation, e.g. by generating parts
of the QOM boilerplate from the QAPI schema.
With this series it's basically pointless to have QOM properties at all.
Instead, you are basically having half of QEMU's backend data model
into a single struct.
So the question is, are we okay with shoveling half of QEMU's backend
data model into a single struct? If so, there are important consequences.
1) QOM basically does not need properties anymore except for devices and
machines (accelerators could be converted to QAPI as well). All
user-creatable objects can be changed to something like chardev's "get a
struct and use it fill in the fields", and only leave properties to
devices and machines.
2) User-creatable objects can have a much more flexible schema. This
means there's no reason to have block device creation as its own command
and struct for example.
The problem with this series is that you are fine with deduplicating
things as a third step, but you cannot be sure that such deduplication
is possible at all. So while I don't have any problems in principle
with the ObjectOptions concept, I don't think it should be committed
without a clear idea of how to do the third step.
In the meanwhile, of course I have no problem with deprecating the
opened and loaded properties.
Paolo