Re: [PATCH v5 1/2] platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe

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On Jan 05, 2024 / 12:45, Klara Modin wrote:
> Den fre 5 jan. 2024 kl 11:26 skrev Shinichiro Kawasaki
> <shinichiro.kawasaki@xxxxxxx>:
> >
> > On Jan 05, 2024 / 09:44, Lukas Wunner wrote:
> > > On Fri, Jan 05, 2024 at 08:18:05AM +0000, Shinichiro Kawasaki wrote:
> > > > --- a/drivers/platform/x86/p2sb.c
> > > > +++ b/drivers/platform/x86/p2sb.c
> > > > @@ -150,6 +153,14 @@ static int p2sb_cache_resources(void)
> > > >     if (!bus)
> > > >             return -ENODEV;
> > > >
> > > > +   /*
> > > > +    * When a device with same devfn exists and it is not P2SB, do not
> > > > +    * touch it.
> > > > +    */
> > > > +   pci_bus_read_config_dword(bus, devfn_p2sb, PCI_CLASS_REVISION, &class);
> > > > +   if (!PCI_POSSIBLE_ERROR(class) && class >> 8 != P2SB_CLASS_CODE)
> > > > +           return -ENODEV;
> > > > +
> > >
> > > The function should probably return if PCI_POSSIBLE_ERROR() is true.
> >
> > At this point, the P2SB device can be still hidden and PCI_POSSIBLE_ERROR() can
> > be true. In that case, the function should not return.
> >
> > > Also I think you can use PCI_CLASS_MEMORY_OTHER, so how about:
> > >
> > >       if (PCI_POSSIBLE_ERROR(class) || class >> 16 != PCI_CLASS_MEMORY_OTHER)
> > >               return -ENODEV;
> > >
> > > Can alternatively use "class >> 8 != PCI_CLASS_MEMORY_OTHER << 8" if you
> > > want to ensure the lowest byte is 0x00.
> >
> > Thanks, it looks the better to use PCI_CLASS_MEMORY_OTHER. Will reflect it when
> > I create the formal fix patch.
> 
> Both of the variants seem to work for me.
> 
> I tried the first patch on its own (059b825c5234), with
>        if (!PCI_POSSIBLE_ERROR(class) && class >> 8 != P2SB_CLASS_CODE)
>                return -ENODEV;
> 
> Then Lukas' suggestion (b97584391ea7), with
>         if (PCI_POSSIBLE_ERROR(class) || class >> 16 != PCI_CLASS_MEMORY_OTHER)
>                 return -ENODEV;
> 
> Tested-by: Klara Modin <klarasmodin@xxxxxxxxx>

Thank you for trying it out. This fix approach looks good :) I will create a
formal patch next week for review.




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