=== patch --dry-run --forward output (proves fix.diff applies cleanly) ===
cmd: cd /usr/src && patch -p1 --dry-run --forward < DF-1511.diff

APPLIES_OK (verified 2026-07-21 on with-src #0 baseline)

--- fix.diff hunk summary ---
@@ -1229,6 +1229,11 @@
+	if (vgasr_priv->handler == NULL ||
+	    vgasr_priv->handler->switchto == NULL) {
+		mutex_unlock(&vgasr_priv->mux_hw_lk);
+		return -ENODEV;
+	}