Re: [PATCH v2 6/8] qom: introduce qdev_new_dynamic()

[Peter Xu <peterx@redhat.com>]

On Mon, Nov 11, 2024 at 03:55:53PM +0000, Daniel P. Berrangé wrote:
> qdev_new() has a failure scenario where it will assert() if given
> an abstract type. Callers which are creating qdevs based on user
> input, or unknown/untrusted type names, must manually check the
> result of qdev_class_is_abstract() before calling qdev_new()
> to propagate an Error, instead of asserting.
> 
> Introduce a qdev_new_dynamic() method which is a counterpart to
> qdev_new() that directly returns an Error, instead of asserting.
> This new method is to be used where the typename is specified
> dynamically by code separate from the immediate caller.
> 
> Do likewise with qdev_try_new_dynamic() as a counterpart to
> qdev_try_new().

Since at it, would it make sense to simply replace qdev_try_new() with
qdev_new_dynamic(), assuming it plays similar role of "it can fail" version
of qdev_new()?

Then instead of four helpers, we stick with two helpers, one that asserts
the qdev new will succeed (qdev_new()), the other one that allows any kind
of errors (qdev_new_dynamic()).  Then we can drop qdev_try_new()
altogether, and avoid adding one more for it too.

The qdev_try_new() four call sites can still pass in errp==NULL, which
should be the old behavior, so we don't need to touch isa/usb callers.

PS: looks like usb_try_new() only has one caller.. so maybe prone to be
dropped altogether..

-- 
Peter Xu