Re: [Qemu-devel] [Qemu-ppc] [PATCH v7 1/3] Add USB option in machine options

[David Gibson <dwg@au1.ibm.com>]

On Wed, Aug 15, 2012 at 10:50:04AM +0800, Li Zhang wrote:
> On Wed, Aug 15, 2012 at 9:47 AM, David Gibson <dwg@au1.ibm.com> wrote:
> > On Wed, Aug 15, 2012 at 09:24:34AM +0800, Li Zhang wrote:
> >> On Wed, Aug 15, 2012 at 8:09 AM, Benjamin Herrenschmidt
> >> <benh@kernel.crashing.org> wrote:
> >> > On Wed, 2012-08-15 at 09:10 +1000, David Gibson wrote:
> >> >> > I see. I will redo this patch. Send out it later. :)
> >> >> > Thanks for your comments.
> >> >>
> >> >> When you do that, please also change the default to make spapr _not_
> >> >> have usb.
> >> >
> >> > FYI, I originally asked for USB as default ... however it looks like at
> >> > this stage the price (performance) is too high so either make it default
> >> > to OFF, or make it default to ON if and only if VGA is also enabled.
> >> >
> >> Got it, I change the default as false, and when VGA is enabled, set
> >> USB option as true.
> >
> > Not quite, actually.  The default should depend on VGA, but the
> > explicit usb= option should always override that.  Having VGA without
> > USB would be unusual, but it should be possible if you specify it
> > explicitly.
> >
> Right, explicit usb= option will override the value.
> I think we can set the usb option value when no usb option is specified.
> For example, we use -machine type=pseries  without usb= option.
> 
> I am considering as the following:
> 
> if (vga_enabled) {
>     set_usb_option(true)
> }

No, this will override the option given on the command line.

> if (usb_enabled(false)) {  //If vga is enabled and "-machine
> type=pseries" is specified, it will get true.
>     pci_create_simple(ohci)
> }

It's much easier than this, you just want
	if (usb_enabled(vga_enabled))

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson