Document addr_unit DAMON sysfs file on DAMON ABI document.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/ABI/testing/sysfs-kernel-mm-damon | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-damon b/Documentation/ABI/testing/sysfs-kernel-mm-damon
index 293197f180ad..40b7735f57d5 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-damon
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-damon
@@ -70,6 +70,13 @@ Description:	Writing a keyword for a monitoring operations set ('vaddr' for
 		Note that only the operations sets that listed in
 		'avail_operations' file are valid inputs.
 
+What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/addr_unit
+Date:		Apr 2025
+Contact:	SeongJae Park <sj@kernel.org>
+Description:	Writing an integer to this file sets the 'address unit'
+		parameter of the given operations set of the context.  Reading
+		the file returns the last-written 'address unit' value.
+
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/monitoring_attrs/intervals/sample_us
 Date:		Mar 2022
 Contact:	SeongJae Park <sj@kernel.org>
-- 
2.39.5