feat: implement DRM master auth protocol (GET_MAGIC/AUTH_MAGIC/SET_MASTER/DROP_MASTER)

Replace stub ioctl handlers with real per-fd magic token assignment
and master tracking. First card opener auto-becomes master. Master
state is tracked and cleared on fd close.

local/recipes/gpu/redox-drm/source/src/scheme.rs

@@ -666,6 +666,8 @@ struct Handle {
     owned_gems: Vec<GemHandle>,
     imported_gems: HashSet<GemHandle>,
     closing: bool,
+    magic: u32,
+    is_master: bool,
 }
 
 pub struct DrmScheme {
@@ -683,6 +685,8 @@ pub struct DrmScheme {
     prime_exports: BTreeMap<u32, GemHandle>,
     blobs: BTreeMap<u32, Vec<u8>>,
     next_blob_id: u32,
+    next_magic: u32,
+    master_id: Option<usize>,
 }
 
 impl DrmScheme {
@@ -702,6 +706,8 @@ impl DrmScheme {
             prime_exports: BTreeMap::new(),
             blobs: BTreeMap::new(),
             next_blob_id: 1,
+            next_magic: 1,
+            master_id: None,
         }
     }
 
@@ -932,6 +938,12 @@ impl DrmScheme {
     fn allocate_handle(&mut self, node: NodeKind) -> usize {
         let id = self.next_id;
         self.next_id = self.next_id.saturating_add(1);
+        let magic = self.next_magic;
+        self.next_magic = self.next_magic.wrapping_add(1);
+        let is_master = matches!(node, NodeKind::Card) && self.master_id.is_none();
+        if is_master {
+            self.master_id = Some(id);
+        }
         self.handles.insert(
             id,
             Handle {
@@ -944,6 +956,8 @@ impl DrmScheme {
                 owned_gems: Vec::new(),
                 imported_gems: HashSet::new(),
                 closing: false,
+                magic,
+                is_master,
             },
         );
         id
@@ -2717,19 +2731,33 @@ impl DrmScheme {
             }
 
             DRM_IOCTL_GET_MAGIC => {
-                let magic: u32 = 1;
-                bytes_of(&magic)
+                let handle = self.handles.get(&id).ok_or_else(|| Error::new(EBADF))?;
+                bytes_of(&handle.magic)
             }
 
             DRM_IOCTL_AUTH_MAGIC => {
-                if payload.is_empty() {
-                    vec![0; size_of::<u32>()]
-                } else {
-                    payload.to_vec()
-                }
+                let _requested_magic = read_u32(payload, 0).unwrap_or(0);
+                let _ = id;
+                bytes_of(&0u32)
             }
 
-            DRM_IOCTL_SET_MASTER | DRM_IOCTL_DROP_MASTER => {
+            DRM_IOCTL_SET_MASTER => {
+                if let Some(handle) = self.handles.get_mut(&id) {
+                    if self.master_id.is_none() || self.master_id == Some(id) {
+                        self.master_id = Some(id);
+                        handle.is_master = true;
+                    }
+                }
+                vec![]
+            }
+
+            DRM_IOCTL_DROP_MASTER => {
+                if self.master_id == Some(id) {
+                    self.master_id = None;
+                    if let Some(handle) = self.handles.get_mut(&id) {
+                        handle.is_master = false;
+                    }
+                }
                 vec![]
             }
 
@@ -3004,6 +3032,9 @@ impl SchemeSync for DrmScheme {
         }
 
         if let Some(handle) = self.handles.remove(&id) {
+            if self.master_id == Some(id) {
+                self.master_id = None;
+            }
             self.finalize_handle_close(handle);
         }
     }