[Qemu-devel] Re: [PATCH 2/2] pci: don't overwrite pci header type.

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 16, 2010 at 06:41:22PM +0000, Blue Swirl wrote:
> On Wed, Jun 16, 2010 at 8:54 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Wed, Jun 16, 2010 at 11:20:02AM +0900, Isaku Yamahata wrote:
> >> On Tue, Jun 15, 2010 at 12:12:07PM +0300, Michael S. Tsirkin wrote:
> >> > On Tue, Jun 15, 2010 at 02:06:46PM +0900, Isaku Yamahata wrote:
> >> > > Don't overwrite pci header type.
> >> > > Otherwise, multi function bit which pci_init_header_type() sets
> >> > > appropriately is lost.
> >> > > Anyway PCI_HEADER_TYPE_NORMAL is zero, so it is unnecessary to zero
> >> > > which is already zero cleared.
> >> > >
> >> > > Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
> >> >
> >> > ...
> >> >
> >> > > diff --git a/hw/apb_pci.c b/hw/apb_pci.c
> >> > > index 31c8d70..cdf3bc2 100644
> >> > > --- a/hw/apb_pci.c
> >> > > +++ b/hw/apb_pci.c
> >> > > @@ -428,7 +428,8 @@ static int pbm_pci_host_init(PCIDevice *d)
> >> > >                   PCI_STATUS_DEVSEL_MEDIUM);
> >> > >      pci_config_set_class(d->config, PCI_CLASS_BRIDGE_HOST);
> >> > >      pci_set_byte(d->config + PCI_HEADER_TYPE,
> >> > > -                 PCI_HEADER_TYPE_NORMAL);
> >> > > +                 (pci_get_byte(d->config + PCI_HEADER_TYPE) &
> >> > > +                  PCI_HEADER_TYPE_MULTI_FUNCTION) | PCI_HEADER_TYPE_NORMAL);
> >> >
> >> > what is this doing?
> >>
> >> It changes the header type to normal device(bit 1-7) without overwriting
> >> multi function bit(bit 8).
> >
> > Don't we know what the multi function bit value is?
> >
> >> Apb host bridge specifies PCI_HEADER_TYPE_BRIDGE in PCIDeviceInfo,
> >> on the other hand pbc_pci_host_init() sets the register
> >> to PCI_HEADER_TYPE_NORMAL.
> >> To be honest I don't know why it does so, but that is what Blue wants.
> >
> > BTW I think it would be prettier to have is_bridge instead of header_type
> > as a qdev property. Agree?
> 
> Good idea.
> 
> >> So I touch only multi function bit(bit 8) and leave other bit (bit 1-7)
> >> unchanged.
> >>
> >> If you don't like this hunk, I'll drop this hunk and leave it to Blue.
> >> What do you think?
> >
> > Blue Swirl, could you comment on this please?
> 
> I'd go for is_bridge and drop the override for header type in apb_pci.c then.

Yes, but what header type does it need?

> >> static PCIDeviceInfo pbm_pci_host_info = {
> >>     .qdev.name = "pbm",
> >>     .qdev.size = sizeof(PCIDevice),
> >>     .init      = pbm_pci_host_init,
> >>     .header_type  = PCI_HEADER_TYPE_BRIDGE,   <<<<< Here
> >> };
> >>
> >> --
> >> yamahata
> >