Re: [PATCH] x86/early-quirks: Scan all functions in early_pci_scan_bus()

[Thorsten Blum]

On Sun, Aug 16, 2026 at 07:25:22AM +0200, Lukas Wunner wrote:
> On Fri, Aug 07, 2026 at 11:46:02AM +0200, Thorsten Blum wrote:
> > early_pci_scan_bus() stops scanning a PCI slot when check_dev_quirk()
> > returns nonzero, which avoids probing functions 1-7 on single-function
> > devices, but also stops scanning when a function is absent on a
> > multifunction device.
> > 
> > This can skip early quirks on multifunction devices with holes in their
> > function numbering.
> > 
> > Check function 0 first, and if it indicates a multifunction device, scan
> > functions 1-7 independently so that absent functions do not cause later
> > ones to be skipped.
> 
> Which device do you need this for?  We should only scan additional
> Functions if a quirk needs to applied to them because this extends
> boot time.  It requires a justification and shouldn't be done "just
> because".

On iMac13,1 and iMac13,2, the BCM4331 AirPort card is behind root port
00:1c.3, also documented by the model list in abb2bafd295f ("x86/quirks:
Add early quirk to reset Apple AirPort card").

Public lspci output for 2012 iMacs [1][2] shows that 00:1c.0, 00:1c.2,
00:1c.3 and 00:1c.4 are present, but 00:1c.1 is missing. The old code
stops at 00:1c.1 and never reaches 00:1c.3, so the AirPort reset quirk
is silently skipped on these machines.

[1] https://forum.libreelec.tv/thread/26799-wifi-not-detected-on-2012-imac-in-11-0/
[2] https://zoringroup.com/forum/5/7170/