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

[David Gibson]

On Wed, Aug 15, 2012 at 01:44:28PM +0800, Li Zhang wrote:
> On Wed, Aug 15, 2012 at 10:57 AM, David Gibson <address@hidden> wrote:
> > On Wed, Aug 15, 2012 at 10:50:04AM +0800, Li Zhang wrote:
> >> On Wed, Aug 15, 2012 at 9:47 AM, David Gibson <address@hidden> 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
> >> >> <address@hidden> 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.
> Oh, I didn't realize that.
> >
> >> 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))
> This is better than mine. :)
> It seems that this patch needs to work with VGA patch together. :)
> I need to modify as that. :)

Not necessarily.  In the initial usb pach you can just make the
default 'false', then just change that one line in the VGA patch.

-- 
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