Paolo Bonzini <[email protected]> writes:
> On 19/05/20 16:55, Markus Armbruster wrote:
>> So far, qdev_realize() supports only devices that plug into a bus:
>> argument @bus cannot be null. Extend it to support bus-less devices,
>> too.
>>
>> qdev_realize_and_unref() remains restricted, because its reference
>> counting would become rather confusing for bus-less devices.
>
> I think it would be fine, you would just rely on the reference held by
> the QOM parent (via the child property).
I took one look at the contract I wrote for it, and balked :)
qdev_realize()'s contract before this patch:
/*
* Realize @dev.
* @dev must not be plugged into a bus.
* Plug @dev into @bus. This takes a reference to @dev.
* If @dev has no QOM parent, make one up, taking another reference.
* On success, return true.
* On failure, store an error through @errp and return false.
*/
bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp)
Simple enough.
This patch merely adds "If @bus, " before "plug". Still simple enough.
qdev_realize_and_unref()'s contract:
/*
* Realize @dev and drop a reference.
* This is like qdev_realize(), except it steals a reference rather
* than take one to plug @dev into @bus. On failure, it drops that
* reference instead. @bus must not be null. Intended use:
* dev = qdev_new();
* [...]
* qdev_realize_and_unref(dev, bus, errp);
* Now @dev can go away without further ado.
*/
bool qdev_realize_and_unref(DeviceState *dev, BusState *bus, Error **errp)
If @bus is null, who gets to hold the stolen reference?
You seem to suggest the QOM parent. What if @dev already has a parent?
Oh, sod it, let's go shopping.
