devnum-util: add new devnum_is_zero() helper

src/basic/devnum-util.c

@@ -83,7 +83,7 @@ int device_path_make_canonical(mode_t mode, dev_t devnum, char **ret) {
 
         assert(ret);
 
-        if (major(devnum) == 0 && minor(devnum) == 0)
+        if (devnum_is_zero(devnum))
                 /* A special hack to make sure our 'inaccessible' device nodes work. They won't have symlinks in
                  * /dev/block/ and /dev/char/, hence we handle them specially here. */
                 return device_path_make_inaccessible(mode, ret);

src/basic/devnum-util.h

@@ -50,3 +50,7 @@ static inline char *format_devnum(dev_t d, char buf[static DEVNUM_STR_MAX]) {
 }
 
 #define FORMAT_DEVNUM(d) format_devnum((d), (char[DEVNUM_STR_MAX]) {})
+
+static inline bool devnum_is_zero(dev_t d) {
+        return major(d) == 0 && minor(d) == 0;
+}

src/basic/terminal-util.c

@@ -979,7 +979,7 @@ int get_ctty_devnr(pid_t pid, dev_t *d) {
                    &ttynr) != 1)
                 return -EIO;
 
-        if (major(ttynr) == 0 && minor(ttynr) == 0)
+        if (devnum_is_zero(ttynr))
                 return -ENXIO;
 
         if (d)

src/libsystemd/sd-device/device-util.c

@@ -15,7 +15,7 @@ int devname_from_devnum(mode_t mode, dev_t devnum, char **ret) {
 
         assert(ret);
 
-        if (major(devnum) == 0 && minor(devnum) == 0)
+        if (devnum_is_zero(devnum))
                 return device_path_make_inaccessible(mode, ret);
 
         r = device_new_from_mode_and_devnum(&dev, mode, devnum);