[PATCH] pci: do not try to assign irq 255

From: Hannes Reinecke
Date: Mon Feb 18 2013 - 05:10:00 EST

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.

Cc: Frederik Himpe <fhimpe@xxxxxxxxx>
Cc: Oliver Neukum <oneukum@xxxxxxx>
Cc: David Haerdeman <david@xxxxxxxxxxx>
Cc: linux-usb@xxxxxxxxxxxxxxx
Cc: linux-pci@xxxxxxxxxxxxxxx
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>

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)
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