linux-kernel - Re: [PATCH] pci: do not try to assign irq 255

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Date:	Tue, 19 Feb 2013 02:13:51 +0100
From:	David Härdeman <david@...deman.nu>
To:	Hannes Reinecke <hare@...e.de>
Cc:	linux-kernel@...r.kernel.org, Frederik Himpe <fhimpe@....ac.be>,
	Oliver Neukum <oneukum@...e.de>, linux-usb@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: do not try to assign irq 255

On Mon, Feb 18, 2013 at 11:09:53AM +0100, Hannes Reinecke wrote:
>The PCI config space reseves a byte for the interrupt line,
>so irq 255 actually refers to 'not set'.
>However, the 'irq' field for struct pci_dev is an integer,
>so the original meaning is lost, causing the system to
>assign an interrupt '255', which fails.
>
>So we should _not_ assign an interrupt value here, and
>allow upper layers to fixup things.
>
>This patch make PCI devices with MSI interrupts only
>(like the xhci device on certain HP laptops) work properly.

Just tested and it works for me. Thank you.

Tested-by: David Härdeman <david@...deman.nu>

>Cc: Frederik Himpe <fhimpe@....ac.be>
>Cc: Oliver Neukum <oneukum@...e.de>
>Cc: David Haerdeman <david@...deman.nu>
>Cc: linux-usb@...r.kernel.org
>Cc: linux-pci@...r.kernel.org
>Signed-off-by: Hannes Reinecke <hare@...e.de>
>
>diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>index 6186f03..a2db887f 100644
>--- a/drivers/pci/probe.c
>+++ b/drivers/pci/probe.c
>@@ -923,7 +923,8 @@ static void pci_read_irq(struct pci_dev *dev)
> 	dev->pin = irq;
> 	if (irq)
> 		pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &irq);
>-	dev->irq = irq;
>+	if (irq < 255)
>+		dev->irq = irq;
> }
> 
> void set_pcie_port_type(struct pci_dev *pdev)
>

-- 
David Härdeman
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