cpu topology: always define CPU topology information

This can result in an empty topology directory in sysfs, and requires
in-kernel users to protect all uses with #ifdef - see
<http://marc.info/?l=linux-netdev&m=120639033904472&w=2>.

The documentation of CPU topology specifies what the defaults should be if
only partial information is available from the hardware.  So we can
provide these defaults as a fallback.

This patch:

- Adds default definitions of the 4 topology macros to <linux/topology.h>
- Changes drivers/base/topology.c to use the topology macros unconditionally
  and to cope with definitions that aren't lvalues
- Updates documentation accordingly

[ From: Andrew Morton <[email protected]>
  - fold now-duplicated code
  - fix layout
]

Signed-off-by: Ben Hutchings <[email protected]>
Cc: Vegard Nossum <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Chandra Seetharaman <[email protected]>
Cc: Suresh Siddha <[email protected]>
Cc: Mike Travis <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: John Hawkes <[email protected]>
Cc: Zhang, Yanmin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/linux/topology.h b/include/linux/topology.h
index 24f3d2282e11..2158fc0d5a56 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -179,4 +179,17 @@ void arch_update_cpu_topology(void);
 #endif
 #endif /* CONFIG_NUMA */
 
+#ifndef topology_physical_package_id
+#define topology_physical_package_id(cpu)	((void)(cpu), -1)
+#endif
+#ifndef topology_core_id
+#define topology_core_id(cpu)			((void)(cpu), 0)
+#endif
+#ifndef topology_thread_siblings
+#define topology_thread_siblings(cpu)		cpumask_of_cpu(cpu)
+#endif
+#ifndef topology_core_siblings
+#define topology_core_siblings(cpu)		cpumask_of_cpu(cpu)
+#endif
+
 #endif /* _LINUX_TOPOLOGY_H */