[PATCH 3/6] perf-events: allow modules to query the maximum number of perf events

[Will Deacon]

An upper bound on the number of perf events is stored in the static
perf_max_events variable. Modules, such as OProfile, can use this
information to allocate and traverse data structures representing
the performance counters for a system.

This patch adds a function to return the value of perf_max_events
and exports this function to modules.

Cc: Ingo Molnar <mingo at elte.hu>
Cc: Peter Zijlstra <peterz at infradead.org>
Signed-off-by: Will Deacon <will.deacon at arm.com>
---
 include/linux/perf_event.h |    1 +
 kernel/perf_event.c        |    6 ++++++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 9547703..a197bc5 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -751,6 +751,7 @@ struct perf_output_handle {
  * Set by architecture code:
  */
 extern int perf_max_events;
+extern int perf_get_max_events(void);
 
 extern const struct pmu *hw_perf_event_init(struct perf_event *event);
 
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 574ee58..464bda6 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -39,6 +39,12 @@
 static DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
 
 int perf_max_events __read_mostly = 1;
+int perf_get_max_events(void)
+{
+	return perf_max_events;
+}
+EXPORT_SYMBOL_GPL(perf_get_max_events);
+
 static int perf_reserved_percpu __read_mostly;
 static int perf_overcommit __read_mostly = 1;
 
-- 
1.6.3.3