Daniel P. Berrangé <berrange@xxxxxxxxxx> writes:
> On Mon, Feb 13, 2023 at 05:01:01PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> The device field is redundant, because QOM path always include device
>> ID when this ID exist.
>
> The flipside to that view is that applications configuring QEMU are
> specifying the device ID for -device (CLI) / device_add (QMP) and
> not the QOM path. IOW, the device ID is the more interesting field
> than QOM path, so feels like the wrong one to be dropping.
QOM path is a reliable way to identify a device. Device ID isn't:
devices need not have one. Therefore, dropping the QOM path would be
wrong.
> Is there any real benefit to dropping this ?
The device ID is a trap for the unwary: relying on it is fine until you
run into a scenario where you have to deal with devices lacking IDs.
I suggested to deprecate it in review of "[PATCH v3 14/15] qapi:
introduce DEVICE_ON event" (Message-ID: <873579x67l.fsf@xxxxxxxxxxxx>).
Quote:
We commonly send both device ID and QOM path, mostly for historical
reasons: the former precede the latter.
There are exceptions, such as query-cpus-fast. Can't say offhand
whether CPUs can be created with IDs.
[...]
I'd be in favour of deprecating and deleting redundant device IDs in QMP
output.
