[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.

Signed-off-by: Enze Li <[email protected]>
---
 samples/damon/mtier.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/samples/damon/mtier.c b/samples/damon/mtier.c
index ac9c24b92ead..27dc88bdf7a0 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;

base-commit: 3d18f3499c48ee94a49589500ce94e41c5acdf4b
-- 
2.55.0