+/*
+ * PCI 2.3 does not specify mask bits for each MSI interrupt. Attempting to
+ * mask all MSI interrupts by clearing the MSI enable bit does not work
+ * reliably as devices without an INTx disable bit will then generate a
+ * level IRQ which will never be cleared.
+ *
+ * Returns 1 if it succeeded in masking the interrupt and 0 if the device
+ * doesn't support MSI masking.
+ */
+static int msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)