node: Fix mask-or operator precedence by replacing + with |

A request for using masks and shifts on the known `0-1-2` constants
defining the minor type of a DRM node resulted in the expression to
maintain the original `+` from first subtracting the current node
type followed by adding the requested node type.  As the subtract of
the current node type was replaced by a mask, the resulting `old_id &
ID_MASK + minor_base` expression is interpreted as `old_id & (ID_MASK
+ minor_base)` because of operator precedence, while it would have been
correctly interpreted as `(old_id & ID_MASK) | minor_base` when the
correct `|` OR operator is used.

src/node/mod.rs

@@ -330,8 +330,8 @@ pub fn dev_path(dev: dev_t, ty: NodeType) -> io::Result<PathBuf> {
     if let Some(dev_name) = devname(dev) {
         let suffix = dev_name.trim_start_matches(|c: char| !c.is_numeric());
         if let Ok(old_id) = suffix.parse::<u32>() {
-            let id_mask = 0b11_1111;
-            let id = old_id & id_mask + ty.minor_base();
+            const ID_MASK: u32 = 0b11_1111;
+            let id = old_id & ID_MASK | ty.minor_base();
             let path = PathBuf::from(format!("/dev/dri/{}{}", ty.minor_name_prefix(), id));
             if path.exists() {
                 return Ok(path);
@@ -363,8 +363,8 @@ pub fn dev_path(dev: dev_t, ty: NodeType) -> io::Result<PathBuf> {
     }
 
     let old_id = minor(dev);
-    let id_mask = 0b11_1111;
-    let id = old_id & id_mask + ty.minor_base();
+    const ID_MASK: u32 = 0b11_1111;
+    let id = old_id & ID_MASK | ty.minor_base();
     let path = PathBuf::from(format!("/dev/dri/{}{}", ty.minor_name_prefix(), id));
     if path.exists() {
         return Ok(path);