[SRU][P][PATCH v2 6/6] UBUNTU: SAUCE: selftests: gpio: gpio-aggregator: add a test case for _sysfs prefix reservation

[Koichiro Den]

BugLink: https://bugs.launchpad.net/bugs/2103496

The kernel doc for gpio-aggregator configfs interface, which was recently
added, states that users should not be able to create an aggregator with a
name prefixed by "_sysfs" via configfs. However, it was found that this
guard does not function as expected (thanks to Dan Carpenter for
identifying and fixing the issue).

Add a test case to verify the guard.

Signed-off-by: Koichiro Den <koichiro.den at canonical.com>
Link: https://lore.kernel.org/r/20250412150119.1461023-1-koichiro.den@canonical.com
Signed-off-by: Bartosz Golaszewski <brgl at bgdev.pl>
(cherry picked from commit 290ffcfe3042dcd5b701a98edd48d7962d35556b gpio/for-next)
Signed-off-by: Koichiro Den <koichiro.den at canonical.com>
---
 tools/testing/selftests/gpio/gpio-aggregator.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/gpio/gpio-aggregator.sh b/tools/testing/selftests/gpio/gpio-aggregator.sh
index f1bab62c4cd2..9b6f80ad9f8a 100755
--- a/tools/testing/selftests/gpio/gpio-aggregator.sh
+++ b/tools/testing/selftests/gpio/gpio-aggregator.sh
@@ -335,6 +335,10 @@ test "$(cat "$CONFIGFS_AGG_DIR/agg0/live")" = 0 || \
 agg_remove_line   agg0 line0
 agg_remove_chip   agg0
 
+echo "1.1.6. Can't instantiate a chip with _sysfs prefix"
+mkdir "$CONFIGFS_AGG_DIR/_sysfs" 2> /dev/null && fail "chip _sysfs unexpectedly created"
+mkdir "$CONFIGFS_AGG_DIR/_sysfs.foo" 2> /dev/null && fail "chip _sysfs.foo unexpectedly created"
+
 echo "1.2. Creation/deletion via sysfs"
 
 echo "1.2.1. Minimum creation/deletion"
-- 
2.45.2