linux-kernel - Re: [tip:x86/urgent] x86/quirks: Add early quirk to reset Apple AirPort card

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Date:	Thu, 9 Jun 2016 17:04:45 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Lukas Wunner <lukas@...ner.de>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, cmilsted@...hat.com,
	"Rafa?? Mi??ecki" <zajec5@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Garrett <mjg59@...f.ucam.org>, m@...s.ch,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/urgent] x86/quirks: Add early quirk to reset Apple
 AirPort card

On 6/9/16, Lukas Wunner <lukas@...ner.de> wrote:
>
> Well, the PCI core would also scan such a bus twice AFAICS.
> And the performance penalty of scanning it twice seems negligible.
> Early quirks can prevent double execution by setting QFLAG_APPLY_ONCE.
> (Three quirks have set that flag already.)
>
> So I think this shouldn't be a concern.

I don't know. I would like see sth like following, and that is simple enough.

Index: linux-2.6/arch/x86/kernel/early-quirks.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/early-quirks.c
+++ linux-2.6/arch/x86/kernel/early-quirks.c
@@ -755,10 +755,16 @@ static int __init check_dev_quirk(int nu
        return 0;
 }

+static unsigned char __initdata scanned[256];
 static void __init early_pci_scan_bus(int bus)
 {
        int slot, func;

+       if (scanned[bus])
+               return;
+
+       scanned[bus] = 1;
+
        /* Poor man's PCI discovery */
        for (slot = 0; slot < 32; slot++)
                for (func = 0; func < 8; func++) {