path: root/kernel
diff options
authorChen Fan <>2016-02-15 12:52:01 +0800
committerRafael J. Wysocki <>2016-03-09 01:23:35 +0100
commite237a5518425155faa508a087f28269f58074b92 (patch)
tree8e8c1d302edc4cfb89dbe9cb2df3b84cbcd5eb9f /kernel
parentf6cede5b49e822ebc41a099fe41ab4989f64e2cb (diff)
x86/ACPI/PCI: Recognize that Interrupt Line 255 means "not connected"
Per the x86-specific footnote to PCI spec r3.0, sec 6.2.4, the value 255 in the Interrupt Line register means "unknown" or "no connection." Previously, when we couldn't derive an IRQ from the _PRT, we fell back to using the value from Interrupt Line as an IRQ. It's questionable whether we should do that at all, but the spec clearly suggests we shouldn't do it for the value 255 on x86. Calling request_irq() with IRQ 255 may succeed, but the driver won't receive any interrupts. Or, if IRQ 255 is shared with another device, it may succeed, and the driver's ISR will be called at random times when the *other* device interrupts. Or it may fail if another device is using IRQ 255 with incompatible flags. What we *want* is for request_irq() to fail predictably so the driver can fall back to polling. On x86, assume 255 in the Interrupt Line means the INTx line is not connected. In that case, set dev->irq to IRQ_NOTCONNECTED so request_irq() will fail gracefully with -ENOTCONN. We found this problem on a system where Secure Boot firmware assigned Interrupt Line 255 to an i801_smbus device and another device was already using MSI-X IRQ 255. This was in v3.10, where i801_probe() fails if request_irq() fails: i801_smbus 0000:00:1f.3: enabling device (0140 -> 0143) i801_smbus 0000:00:1f.3: can't derive routing for PCI INT C i801_smbus 0000:00:1f.3: PCI INT C: no GSI genirq: Flags mismatch irq 255. 00000080 (i801_smbus) vs. 00000000 (megasa) CPU: 0 PID: 2487 Comm: kworker/0:1 Not tainted 3.10.0-229.el7.x86_64 #1 Hardware name: FUJITSU PRIMEQUEST 2800E2/D3736, BIOS PRIMEQUEST 2000 Serie5 Call Trace: dump_stack+0x19/0x1b __setup_irq+0x54a/0x570 request_threaded_irq+0xcc/0x170 i801_probe+0x32f/0x508 [i2c_i801] local_pci_probe+0x45/0xa0 i801_smbus 0000:00:1f.3: Failed to allocate irq 255: -16 i801_smbus: probe of 0000:00:1f.3 failed with error -16 After aeb8a3d16ae0 ("i2c: i801: Check if interrupts are disabled"), i801_probe() will fall back to polling if request_irq() fails. But we still need this patch because request_irq() may succeed or fail depending on other devices in the system. If request_irq() fails, i801_smbus will work by falling back to polling, but if it succeeds, i801_smbus won't work because it expects interrupts that it may not receive. Signed-off-by: Chen Fan <> Acked-by: Thomas Gleixner <> Acked-by: Bjorn Helgaas <> Signed-off-by: Rafael J. Wysocki <>
Diffstat (limited to 'kernel')
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 841187239adc..e79e60f50bce 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1609,6 +1609,9 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
struct irq_desc *desc;
int retval;
+ if (irq == IRQ_NOTCONNECTED)
+ return -ENOTCONN;
* Sanity-check: shared interrupts must pass in a real dev-ID,
* otherwise we'll have trouble later trying to figure out
@@ -1699,9 +1702,13 @@ EXPORT_SYMBOL(request_threaded_irq);
int request_any_context_irq(unsigned int irq, irq_handler_t handler,
unsigned long flags, const char *name, void *dev_id)
- struct irq_desc *desc = irq_to_desc(irq);
+ struct irq_desc *desc;
int ret;
+ if (irq == IRQ_NOTCONNECTED)
+ return -ENOTCONN;
+ desc = irq_to_desc(irq);
if (!desc)
return -EINVAL;