selftests/damon/_damon_sysfs: support DAMOS target_nid setup

_damon_sysfs.py contains code for test-purpose DAMON sysfs interface
control.  Add support of DAMOS action destination target_nid setup for
more tests.

Link: https://lkml.kernel.org/r/20250720171652.92309-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/_damon_sysfs.py

@@ -395,6 +395,7 @@ class Damos:
     ops_filters = None
     filters = None
     apply_interval_us = None
+    target_nid = None
     dests = None
     idx = None
     context = None
@@ -404,7 +405,7 @@ class Damos:
 
     def __init__(self, action='stat', access_pattern=DamosAccessPattern(),
                  quota=DamosQuota(), watermarks=DamosWatermarks(),
-                 core_filters=[], ops_filters=[], filters=[],
+                 core_filters=[], ops_filters=[], filters=[], target_nid=0,
                  dests=DamosDests(), apply_interval_us=0):
         self.action = action
         self.access_pattern = access_pattern
@@ -423,6 +424,7 @@ class Damos:
         self.filters = DamosFilters(name='filters', filters=filters)
         self.filters.scheme = self
 
+        self.target_nid = target_nid
         self.dests = dests
         self.dests.scheme = self
 
@@ -462,6 +464,11 @@ class Damos:
         if err is not None:
             return err
 
+        err = write_file(os.path.join(self.sysfs_dir(), 'target_nid'), '%d' %
+                         self.target_nid)
+        if err is not None:
+            return err
+
         err = self.dests.stage()
         if err is not None:
             return err