On 30 January 2013 20:08, Michael S. Tsirkin <m...@redhat.com> wrote: > Anthony wrote: >> Nope. You can use composition: >> >> QXLDevice is-a VGACommonState >> >> QXLPCI is-a PCIDevice >> has-a QXLDevice > > But why like this? > The distinction is artificial, isn't it?
I think it's the wrong way round. QXLPCI should has-a PCI interface (the physical card possesses an edge connector which fits a PCI socket; it is not the case that the physical card is a kind of edge connector). Having PCI card models inherit from PCIDevice is just a convenient (but misleading) shortcut, and that is what we should drop if it turns out that we should be inheriting from some other class. Or you could make them both has-a; I don't know enough about QXLDevice to know if it should be is-a or has-a. -- PMM
