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Date: Mon, 17 Aug 2026 10:19:12 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Thorsten Blum <thorsten.blum@linux.dev>
Cc: Bjorn Helgaas <bhelgaas@google.com>, Thomas Gleixner <tglx@kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>, Jesse Barnes <jbarnes@hobbes.lan>,
	Ingo Molnar <mingo@elte.hu>, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/early-quirks: Scan all functions in
 early_pci_scan_bus()
Message-ID: <aoLEAD_8GgzuDtYK@wunner.de>
References: <20260807094601.263450-2-thorsten.blum@linux.dev>
 <aoFJwldO-_qttr0P@wunner.de>
 <aoIiEZmqsOOwS6KX@linux.dev>
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In-Reply-To: <aoIiEZmqsOOwS6KX@linux.dev>

On Sun, Aug 16, 2026 at 10:48:17PM +0200, Thorsten Blum wrote:
> 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.
> > 
> > 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/

Thanks for the explanation.  Please include all of this information
in the commit message when respinning.