Re: [PATCH] hw/mips: Improve the default USB settings in the loongson3-virt machine

[Thomas Huth]

On 08/06/2023 20.31, Michael Tokarev wrote:
> 07.06.2023 13:26, Thomas Huth wrote:
> > On 25/05/2023 08.47, Thomas Huth wrote:
> > > It's possible to compile QEMU without the USB devices (e.g. when using
> > > "--without-default-devices" as option for the "configure" script).
> > > To be still able to run the loongson3-virt machine in default mode with
> > > such a QEMU binary, we have to check here for the availability of the
> > > devices first before instantiating them.
> > >
> > > Signed-off-by: Thomas Huth <thuth@redhat.com>
> > > ---
> > >   The alternative would be to use a "#ifdef CONFIG_USB_OHCI_PCI" etc.
> > >   ... not sure what is nicer ... what do you think?
> > >
> > >   hw/mips/loongson3_virt.c | 10 +++++++---
> > >   1 file changed, 7 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/hw/mips/loongson3_virt.c b/hw/mips/loongson3_virt.c
> > > index 216812f660..a0afb17030 100644
> > > --- a/hw/mips/loongson3_virt.c
> > > +++ b/hw/mips/loongson3_virt.c
> > > @@ -447,10 +447,14 @@ static inline void 
> > > loongson3_virt_devices_init(MachineState *machine,
> > >       pci_vga_init(pci_bus);
> > > -    if (defaults_enabled()) {
> > > +    if (defaults_enabled() && module_object_class_by_name("pci-ohci")) {
> > >           pci_create_simple(pci_bus, -1, "pci-ohci");
> > > -        usb_create_simple(usb_bus_find(-1), "usb-kbd");
> > > -        usb_create_simple(usb_bus_find(-1), "usb-tablet");
> > > +        if (module_object_class_by_name("usb-kbd")) {
> > > +            usb_create_simple(usb_bus_find(-1), "usb-kbd");
> > > +        }
> > > +        if (module_object_class_by_name("usb-tablet")) {
> > > +            usb_create_simple(usb_bus_find(-1), "usb-tablet");
> > > +        }
>
> It looks like kbd/tablet don't need to have an if around, because
> hw/usb/usb-hid.c is always compiled when CONFIG_USB is enabled,
> and enabling CONFIG_USB_OHCI automatically selects CONFIG_USB.

Oh, right! So this can be simplified, indeed.

> I guess this whole code can be guarded by #if CONFIG_USB_OHCI..#endif,
> instead of using runtime checking of device availability.

Yes, that's the alternative ... I'll respin the patch with that to see how 
it looks like.

> Notes:
>
> Other places don't check if ohci or other usb controllers are available.

Those likely use "select" instead of "imply" in their Kconfig, so the OHCI 
controller is always included.

> We have TYPE_PCI_OHCI #define which isn't used in places where pci-ohci
> is requested, - probably need to move it to a common header (it is
> defined in hw/usb/hcd-ohci-pci.c now).

Yes, sounds like a cleanup that could be done in an additional patch.

> roms/config.seabios-128k turns USB_OHCI off.

That's the config of the seabios ROM - not (directly) related to the config 
of the QEMU binaries.

 Thomas