Am 30.01.2013 18:29, schrieb Anthony Liguori: > Andreas Färber <afaerber@xxxxxxx> writes: > >> Am 30.01.2013 17:33, schrieb Anthony Liguori: >>> Gerd Hoffmann <kraxel@xxxxxxxxxx> writes: >>> >>>>> hw/qxl.c: portio_list_add(qxl_vga_port_list, >>>>> pci_address_space_io(dev), 0x3b0); >>>>> hw/vga.c: portio_list_add(vga_port_list, address_space_io, 0x3b0); >>>> >>>> That reminds me I should solve this in a more elegant way. >>>> >>>> qxl takes over the vga io ports. The reason it does this is because qxl >>>> switches into vga mode in case the vga ports are accessed while not in >>>> vga mode. After doing the check (and possibly switching mode) the vga >>>> handler is called to actually handle it. >>> >>> The best way to handle this would be to remodel how we do VGA. >>> >>> Make VGACommonState a proper QOM object and use it as the base class for >>> QXL, CirrusVGA, QEMUVGA (std-vga), and VMwareVGA. >> >> That would require polymorphism since we already need to derive from >> PCIDevice or ISADevice respectively for interfacing with the bus... > > Nope. You can use composition: > > QXLDevice is-a VGACommonState > > QXLPCI is-a PCIDevice > has-a QXLDevice > >> Modern object-oriented languages have tried to avoid multi-inheritence >> due to arising complications, I thought. Wouldn't object if someone >> wanted to do the dirty implementation work though. ;) > > There is no need for MI. > >> Another such example is EHCI, with PCIDevice and SysBusDevice frontends, >> sharing an EHCIState struct and having helper functions operating on >> that core state only. Quite a few device share such a pattern today >> actually (serial, m48t59, ...). > > Yes, this is all about chipset modelling. Chipsets should derive from > device and then be embedded in the appropriate bus device. > > For instance. > > SerialState is-a DeviceState > > ISASerialState is-a ISADevice, has-a SerialState > MMIOSerialState is-a SysbusDevice, has-a SerialState Okay, but I don't like that both are transitively DeviceState then. It's much too easy to add / hot-add the wrong device then, especially when dropping no_user. Andreas > This is what we're doing in practice, we just aren't modeling the > chipsets and we're open coding the relationships (often in subtley > different ways). > > Regards, > > Anthony Liguori -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
