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

[Blue Swirl]

On Wed, Jun 16, 2010 at 8:54 AM, Michael S. Tsirkin <address@hidden> 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 <address@hidden>
>> >
>> > ...
>> >
>> > > 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.

>> 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
>