Re: [kvm-unit-tests PATCH 10/14] pci: add bdf helpers

[Peter Xu <peterx@redhat.com>]

On Thu, Oct 20, 2016 at 02:55:39PM +0200, Andrew Jones wrote:
> On Fri, Oct 14, 2016 at 08:40:48PM +0800, Peter Xu wrote:
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  lib/pci.h | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/lib/pci.h b/lib/pci.h
> > index b8755ff..6a1c3c9 100644
> > --- a/lib/pci.h
> > +++ b/lib/pci.h
> > @@ -18,6 +18,12 @@ enum {
> >  #define PCI_BAR_NUM                     (6)
> >  #define PCI_DEVFN_MAX                   (256)
> >  
> > +#define PCI_BDF_GET_DEVFN(x)            ((x) & 0xff)
> > +#define PCI_BDF_GET_BUS(x)              (((x) >> 8) & 0xff)
> > +#define PCI_SLOT(devfn)                 (((devfn) >> 3) & 0x1f)
> > +#define PCI_FUNC(devfn)                 ((devfn) & 0x07)
> > +#define PCI_BUILD_BDF(bus, devfn)       ((bus << 8) | (devfn))
> 
> As I mention frequently; I know nothing about PCI, but this doesn't
> look right to me. DEVFN should be defined as
> 
>  #define PCI_DEVFN(slot, func)   ((((slot) & 0x1f) << 3) | ((func) & 0x07))
> 
> Care to explain these? Please provide the explanation in the commit
> message to along with a motivation for adding them.

Looks like the above lines are not conflicting? E.g., the above patch
(PCI_SLOT and PCI_FUNC) provides way to abstract slot/function out of
devfn value, while the one you mentioned (PCI_DEVFN) should be the
builder macro that builds a devfn value from its slot and function?

However... I just found that I didn't use
PCI_SLOT/PCI_FUNC/PCI_BUILD_BDF macros in the following patches, so
maybe I should just remove the last three of them...

Thanks,

-- peterx