Re: [PATCH v1 2/4] x86/pci: Re-use new dmi_get_bios_year() helper

[Rafael J. Wysocki]

On Wed, Feb 28, 2018 at 11:29 AM, Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> On Mon, 2018-02-26 at 17:28 +0100, Jean Delvare wrote:
>
>> > -   if (dmi_get_date(DMI_BIOS_DATE, &year, NULL, NULL) && year
>> > < 2008) {
>> > -           if (iomem_resource.end <= 0xffffffff)
>> > -                   pci_use_crs = false;
>> > -   }
>> > +   if ((dmi_get_bios_year() < 2008) && (iomem_resource.end <=
>> > 0xffffffff))
>> > +           pci_use_crs = false;
>>
>> You are changing the behavior here, when DMI does not provide a BIOS
>> date. Beforehand, the test would fail and pci_use_crs would be left
>> alone. After your change, dmi_get_bios_year() will return 0, and
>> "0 < 2008" is true, so pci_use_crs is set to false.
>
> Hmm... Indeed.
>
>> I have no opinion on what this driver should do in such case,
>
> I would assume that no BIOS date is related to prehistoric firmwares and
>  using _CRS would sound weird on them.

Careful here.

You seem to be assuming that the DMI information is always valid
and/or complete which is know to not be the case sometimes.