From: "Nakajima, Jun" <jun.nakajima@intel.com>

Doing this for Len, who is on vacation. We would like to thank the
people who provided debugging info such as acpidmp, dmidecode, and
demsg. This is one of our findings, and we believe this would fix some
interrupt problems (with USB, for example) with ACPI enabled, especially
when the dmesg reads like:

ACPI: PCI Interrupt Link [ALKA] enabled at IRQ 0
ACPI: PCI Interrupt Link [ALKB] enabled at IRQ 0
ACPI: PCI Interrupt Link [ALKC] enabled at IRQ 0
ACPI: PCI Interrupt Link [ALKD] enabled at IRQ 0

Basically we assumed that _CRS returned the one we set with _SRS, when
setting up a PCI interrupt link device, but that's not the case with
some AML codes. Some of them always return 0.
Attached is a patch against 2.4.23-pre1. It should be easy to apply this
to 2.6. 

DESC
acpi fix
EDESC
From: Chris Wright <chrisw@osdl.org>

This patch wouldn't compile with CONFIG_ACPI_DEBUG=y



 drivers/acpi/pci_link.c |   32 ++++++++++++++++++++++++++------
 1 files changed, 26 insertions(+), 6 deletions(-)

diff -puN drivers/acpi/pci_link.c~acpi-pci-routing-fixes drivers/acpi/pci_link.c
--- 25/drivers/acpi/pci_link.c~acpi-pci-routing-fixes	2003-09-03 23:40:23.000000000 -0700
+++ 25-akpm/drivers/acpi/pci_link.c	2003-09-03 23:40:23.000000000 -0700
@@ -220,7 +220,6 @@ acpi_pci_link_check_current (
 	return AE_CTRL_TERMINATE;
 }
 
-
 static int
 acpi_pci_link_get_current (
 	struct acpi_pci_link	*link)
@@ -279,6 +278,31 @@ end:
 	return_VALUE(result);
 }
 
+static int
+acpi_pci_link_try_get_current (
+	struct acpi_pci_link *link,
+	int irq)
+{
+	int result;
+
+	ACPI_FUNCTION_TRACE("acpi_pci_link_try_get_current");
+
+	result = acpi_pci_link_get_current(link);
+	if (result && link->irq.active) {
+ 		return_VALUE(result);
+ 	}
+
+	if (!link->irq.active) {
+		ACPI_DEBUG_PRINT((ACPI_DB_ERROR, "No active IRQ resource found\n"));
+		printk(KERN_WARNING "_CRS returns NULL! Using IRQ %d for "
+				"device (%s [%s]).\n",
+				irq, acpi_device_name(link->device),
+				acpi_device_bid(link->device));
+		link->irq.active = irq;
+	}
+
+	return 0;
+}
 
 static int
 acpi_pci_link_set (
@@ -361,7 +385,7 @@ acpi_pci_link_set (
 	}
 
 	/* Make sure the active IRQ is the one we requested. */
-	result = acpi_pci_link_get_current(link);
+	result = acpi_pci_link_try_get_current(link, irq);
 	if (result) {
 		return_VALUE(result);
 	}
@@ -574,10 +598,6 @@ acpi_pci_link_add (
 		else
 			printk(" %d", link->irq.possible[i]);
 	}
-	if (!link->irq.active)
-		printk(", disabled");
-	else if (!found)
-		printk(", enabled at IRQ %d", link->irq.active);
 	printk(")\n");
 
 	/* TBD: Acquire/release lock */

_