linux-kernel - Re: [PATCH v2] pci: fix unavailable irq number 255 reported by BIOS

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Date:	Tue, 26 Jan 2016 10:51:56 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Chen Fan <chen.fan.fnst@...fujitsu.com>
cc:	Bjorn Helgaas <helgaas@...nel.org>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, rjw@...ysocki.net, lenb@...nel.org,
	izumi.taku@...fujitsu.com, wency@...fujitsu.com,
	caoj.fnst@...fujitsu.com, ddaney.cavm@...il.com,
	okaya@...eaurora.org, bhelgaas@...gle.com,
	jiang.liu@...ux.intel.com, linux-pci@...r.kernel.org
Subject: Re: [PATCH v2] pci: fix unavailable irq number 255 reported by
 BIOS

On Tue, 26 Jan 2016, Chen Fan wrote:
> On 01/26/2016 04:26 PM, Thomas Gleixner wrote:
> > > >   	if (gsi < 0) {
> > > > -		if (acpi_isa_register_gsi(dev))
> > > > +#ifdef CONFIG_X86
> > > > +		/*
> > > > +		 * The Interrupt Line value of 0xff is defined to mean
> > > > "unknown"
> > > > +		 * or "no connection" (PCI 3.0, Section 6.2.4, footnote on
> > > > page
> > > > +		 * 223), using ~0U as invalid IRQ.
> > > > +		 */
> > And why would this be x86 specific? PCI3.0 is architecture independent,
> > right?
> quoting the spec document:
> "For x86 based PCs, the values in this register correspond to IRQ numbers
> (0-15) of the standard dual
> 8259 configuration. The value 255 is defined as meaning "unknown" or "no
> connection" to the interrupt
> controller. Values between 15 and 254 are reserved."

So if that is x86 specific then it needs to be documented proper. The fact
that the comment is inside the #ifdef x86 does not tell.

Thanks,

	tglx