Sometimes asking a colleague is even faster than StackOverflow
:)
Here's my solution:
forms.py
class BaseFormSet(BaseInlineFormSet):
def __init__(self, *args, **kwargs):
self.request = kwargs.pop("request", None)
super(BaseFormSet, self).__init__(*args, **kwargs)
views.py
MyFormSet = inlineformset_factory(ParentEntity, ChildEntity, formset=BaseFormSet, form=ChildForm, extra=2, max_num=max_num, can_delete=False)
...
formset = MyFormSet(request.POST, instance=obj, request=request)