diff --git a/src/basic/devnum-util.h b/src/basic/devnum-util.h
index e109de99136..0efca567809 100644
--- a/src/basic/devnum-util.h
+++ b/src/basic/devnum-util.h
@@ -9,6 +9,9 @@
 
 int parse_devnum(const char *s, dev_t *ret);
 
+#define DEVNUM_MAJOR_MAX ((UINT32_C(1) << 12) - 1U)
+#define DEVNUM_MINOR_MAX ((UINT32_C(1) << 20) - 1U)
+
 /* glibc and the Linux kernel have different ideas about the major/minor size. These calls will check whether the
  * specified major is valid by the Linux kernel's standards, not by glibc's. Linux has 20bits of minor, and 12 bits of
  * major space. See MINORBITS in linux/kdev_t.h in the kernel sources. (If you wonder why we define _y here, instead of
@@ -18,14 +21,14 @@ int parse_devnum(const char *s, dev_t *ret);
 #define DEVICE_MAJOR_VALID(x)                                           \
         ({                                                              \
                 typeof(x) _x = (x), _y = 0;                             \
-                _x >= _y && _x < (UINT32_C(1) << 12);                   \
+                _x >= _y && _x <= DEVNUM_MAJOR_MAX;                     \
                                                                         \
         })
 
 #define DEVICE_MINOR_VALID(x)                                           \
         ({                                                              \
                 typeof(x) _x = (x), _y = 0;                             \
-                _x >= _y && _x < (UINT32_C(1) << 20);                   \
+                _x >= _y && _x <= DEVNUM_MINOR_MAX;                     \
         })
 
 int device_path_make_major_minor(mode_t mode, dev_t devnum, char **ret);
@@ -54,3 +57,6 @@ static inline char *format_devnum(dev_t d, char buf[static DEVNUM_STR_MAX]) {
 static inline bool devnum_is_zero(dev_t d) {
         return major(d) == 0 && minor(d) == 0;
 }
+
+#define DEVNUM_TO_PTR(u) ((void*) (uintptr_t) (u))
+#define PTR_TO_DEVNUM(p) ((dev_t) ((uintptr_t) (p)))
diff --git a/src/test/test-devnum-util.c b/src/test/test-devnum-util.c
index ebef794001b..782f15d86ff 100644
--- a/src/test/test-devnum-util.c
+++ b/src/test/test-devnum-util.c
@@ -121,4 +121,21 @@ TEST(devnum_format_str) {
         test_devnum_format_str_one(makedev(4095, 1048575), "4095:1048575");
 }
 
+TEST(devnum_to_ptr) {
+        dev_t m = makedev(0, 0);
+        ASSERT_EQ(major(m), 0U);
+        ASSERT_EQ(minor(m), 0U);
+        ASSERT_EQ(m, PTR_TO_DEVNUM(DEVNUM_TO_PTR(m)));
+
+        m = makedev(DEVNUM_MAJOR_MAX, DEVNUM_MINOR_MAX);
+        ASSERT_EQ(major(m), DEVNUM_MAJOR_MAX);
+        ASSERT_EQ(minor(m), DEVNUM_MINOR_MAX);
+        ASSERT_EQ(m, PTR_TO_DEVNUM(DEVNUM_TO_PTR(m)));
+
+        m = makedev(5, 8);
+        ASSERT_EQ(major(m), 5U);
+        ASSERT_EQ(minor(m), 8U);
+        ASSERT_EQ(m, PTR_TO_DEVNUM(DEVNUM_TO_PTR(m)));
+}
+
 DEFINE_TEST_MAIN(LOG_INFO);