[PATCH] perf Documentation: clarify sysfs event names characters

[Randy Dunlap]

Specify that perf event names in sysfs must not contain mixed lower and
upper case characters and that they may contain numbers, ".", "_",
or "-" as well.

Fixes: 785623ee855e ("perf Document: Sysfs event names must be lower or upper case")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: linux-perf-users@xxxxxxxxxxxxxxx
---
 Documentation/ABI/testing/sysfs-bus-event_source-devices-events |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff -- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
--- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
+++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
@@ -37,11 +37,13 @@ Description:	Per-pmu performance monitor
 		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
+		As performance monitoring event names are case insensitive
+		in the perf tool, the perf tool only looks for all lower
+		case or all 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.
+		name of the event here is either completely lower or upper
+		case, with no mixed-case characters. Numbers, '.', '_', and
+		'-' are also allowed.
 
 		File contents: