On Thu, Aug 11, 2016 at 12:36:37PM -0400, Tejun Heo wrote:

quoted

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 7461a58..dcf2c72 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c

@@ -2524,7 +2524,7 @@ static int ahci_host_activate_multi_irqs(struct ata_host *host,
 
 		/* Do not receive interrupts sent by dummy ports */
 		if (!pp) {
-			disable_irq(irq + i);
+			disable_irq(irq);
 			continue;
 		}

I'm not following.  The driver at that point has irqs in the range
[@irq, @irq + @host->n_ports - 1] and is trying to activate them and
the above code block disables irq for a port which should be skipped.
Why wouldn't it need to be indexed?

Because ahci_irq_vector does that indexing already.  This call changed
when Dan added ahci_irq_vector to support the MSI-X case - since
then ahci_irq_vector either does the base irq + index logic for
MSI or uses the msix_entries array for MSI-X, and irq contains the
result of that operation.