lib: cpu_rmap: CPU affinity reverse-mapping

When initiating I/O on a multiqueue and multi-IRQ device, we may want
to select a queue for which the response will be handled on the same
or a nearby CPU.  This requires a reverse-map of IRQ affinity.  Add
library functions to support a generic reverse-mapping from CPUs to
objects with affinity and the specific case where the objects are
IRQs.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/Kconfig b/lib/Kconfig
index 0ee67e08ad3e..8334342e0d05 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -201,6 +201,10 @@ config DISABLE_OBSOLETE_CPUMASK_FUNCTIONS
        bool "Disable obsolete cpumask functions" if DEBUG_PER_CPU_MAPS
        depends on EXPERIMENTAL && BROKEN
 
+config CPU_RMAP
+        bool
+        depends on SMP
+
 #
 # Netlink attribute parsing support is select'ed if needed
 #