Re: [PATCH v2 3/4] PCI/ACPI: Add Broadcom bcm2711 MCFG quirk

[Florian Fainelli]

On 8/24/2021 11:39 PM, Jeremy Linton wrote:
> Hi,
>
> On 8/22/21 3:53 AM, Florian Fainelli wrote:
> > On 8/19/2021 11:56 PM, Jeremy Linton wrote:
> > > Now that there is a bcm2711 quirk, it needs to be enabled when the
> > > MCFG is missing. Use an ACPI namespace _DSD property
> > > "linux-ecam-quirk-id" as an alternative to the MCFG OEM.
> > >
> > > Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> > > ---
> > >   drivers/acpi/pci_mcfg.c | 13 +++++++++++++
> > >   1 file changed, 13 insertions(+)
> > >
> > > diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
> > > index 53cab975f612..4b991ee5c66c 100644
> > > --- a/drivers/acpi/pci_mcfg.c
> > > +++ b/drivers/acpi/pci_mcfg.c
> > > @@ -169,6 +169,9 @@ static struct mcfg_fixup mcfg_quirks[] = {
> > >       ALTRA_ECAM_QUIRK(1, 13),
> > >       ALTRA_ECAM_QUIRK(1, 14),
> > >       ALTRA_ECAM_QUIRK(1, 15),
> > > +
> > > +    { "bcm2711", "", 0, 0, MCFG_BUS_ANY, &bcm2711_pcie_ops,
> > > +      DEFINE_RES_MEM(0xFD500000, 0xA000) },
> > >   };
> > >   static char mcfg_oem_id[ACPI_OEM_ID_SIZE];
> > > @@ -198,8 +201,18 @@ static void pci_mcfg_apply_quirks(struct 
> > > acpi_pci_root *root,
> > >       u16 segment = root->segment;
> > >       struct resource *bus_range = &root->secondary;
> > >       struct mcfg_fixup *f;
> > > +    const char *soc;
> > >       int i;
> > > +    /*
> > > +     * This may be a machine with a PCI/SMC conduit, which means it 
> > > doesn't
> > > +     * have an MCFG. Use an ACPI namespace definition instead.
> > > +     */
> > > +    if (!fwnode_property_read_string(acpi_fwnode_handle(root->device),
> > > +                     "linux-ecam-quirk-id", &soc)) {
> > > +        memcpy(mcfg_oem_id, soc, ACPI_OEM_ID_SIZE);
> >
> > Being super paranoid here, can we use one of the "safe" string copy 
> > routines here just in case?
>
> Hmm, I went around with this a bit when I first wrote it, because the 
> OEM fields in the ACPI tables are fixed len and don't have null 
> termination. Maybe the right thing to do here is verify the string size 
> is at least as long as the OEM_ID_SIZE and then continue to use the memcpy.

Sure, sounds entirely reasonable to me.
--
Florian