[PATCH v2 1/2] selftests/damon/_damon_sysfs: support kdamond refresh_ms

[SJ Park <sj@kernel.org>]

From: Ruslan Valiyev <linuxoid@gmail.com>

The Kdamond class has no way to set the kdamond-level 'refresh_ms' sysfs
file, which makes DAMON periodically update the read-only sysfs files
(DAMOS stats, tuned monitoring intervals and the kdamond pid) on its own.

Add a 'refresh_ms' parameter to Kdamond.  When it is set (including to
zero, to disable the periodic update), write it before turning the
kdamond on, so tests can exercise the auto-update behavior.  Leaving it
unset keeps the previous behavior of not touching the file, so callers
running against kernels without the feature are unaffected.

Link: https://lore.kernel.org/20260602131217.2210912-2-linuxoid@gmail.com
Signed-off-by: Ruslan Valiyev <linuxoid@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: SJ Park <sj@kernel.org>
---
 tools/testing/selftests/damon/_damon_sysfs.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/damon/_damon_sysfs.py b/tools/testing/selftests/damon/_damon_sysfs.py
index c197ab99bcc0a..e6a2265d721e8 100644
--- a/tools/testing/selftests/damon/_damon_sysfs.py
+++ b/tools/testing/selftests/damon/_damon_sysfs.py
@@ -698,12 +698,14 @@ class DamonCtx:
 class Kdamond:
     state = None
     pid = None
+    refresh_ms = None
     contexts = None
     idx = None      # index of this kdamond between siblings
     kdamonds = None # parent
 
-    def __init__(self, contexts=[]):
+    def __init__(self, contexts=[], refresh_ms=None):
         self.contexts = contexts
+        self.refresh_ms = refresh_ms
         for idx, context in enumerate(self.contexts):
             context.idx = idx
             context.kdamond = self
@@ -726,6 +728,11 @@ class Kdamond:
             err = context.stage()
             if err is not None:
                 return err
+        if self.refresh_ms is not None:
+            err = write_file(os.path.join(self.sysfs_dir(), 'refresh_ms'),
+                             '%d' % self.refresh_ms)
+            if err is not None:
+                return err
         err = write_file(os.path.join(self.sysfs_dir(), 'state'), 'on')
         if err is not None:
             return err
-- 
2.47.3