From fb14504f2e8fdbf5efe4faf0051397d180bff4af Mon Sep 17 00:00:00 2001
From: Enze Li <lienze@kylinos.cn>
Date: Mon, 31 Aug 2026 07:26:09 -0700
Subject: [PATCH] samples/damon/mtier: add comment for struct region_range

The mtier sample defines a local struct region_range using phys_addr_t
instead of damon_addr_range which uses unsigned long.  Add a comment
explaining the rationale: on 32-bit systems with more than 4GiB memory,
phys_addr_t will be 64-bit while unsigned long is 32-bit.

Link: https://lore.kernel.org/20260831142611.77572-8-sj@kernel.org
Signed-off-by: Enze Li <lienze@kylinos.cn>
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hari Mishal <harimishal1@gmail.com>
Cc: Jaeyeon Lee <jaeyeon.lee.dev@gmail.com>
Cc: Li Youhong <liyouhong@kylinos.cn>
Cc: Shuah Khan <shuah@kernel.org>
Cc: "Zenghui Yu (Huawei)" <zenghui.yu@linux.dev>
Cc: zhaozhengzhuo <zhaozhengzhuo@uniontech.com>
---
 samples/damon/mtier.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/samples/damon/mtier.c b/samples/damon/mtier.c
index d1123ebbfab9..bea45c87cc9b 100644
--- a/samples/damon/mtier.c
+++ b/samples/damon/mtier.c
@@ -52,6 +52,11 @@ module_param(detect_node_addresses, bool, 0600);
 
 static struct damon_ctx *ctxs[2];
 
+/*
+ * Use phys_addr_t instead of damon_addr_range (unsigned long) for physical
+ * addresses.  On 32-bit systems with more than 4GB memory, phys_addr_t will
+ * be 64-bit while unsigned long is 32-bit.
+ */
 struct region_range {
 	phys_addr_t start;
 	phys_addr_t end;