perf Document: Sysfs event names must be lower or upper case

To avoid directory scans in perf it is going to be assumed that sysfs
event names are either lower or upper case.

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Link: https://lore.kernel.org/r/20240502213507.2339733-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
index 77de58d03822e4769cebb0363bd4cef7ba8b1428..e7efeab2ee83ce79eaaa0d9a71f32ce93bcb93b1 100644 (file)
--- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
+++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
@@ -37,6 +37,12 @@ Description: Per-pmu performance monitoring events specific to the running syste
                performance monitoring event supported by the <pmu>. The name
                of the file is the name of the event.
 
+               As performance monitoring event names are case
+               insensitive in the perf tool, the perf tool only looks
+               for lower or upper case event names in sysfs to avoid
+               scanning the directory. It is therefore required the
+               name of the event here is either lower or upper case.
+
                File contents:
 
                        <term>[=<value>][,<term>[=<value>]]...