diff --git a/src/device/mod.rs b/src/device/mod.rs
index 09a689a..9d2d49f 100644
--- a/src/device/mod.rs
+++ b/src/device/mod.rs
@@ -59,15 +59,6 @@ pub trait Device: Send {
     fn color_correction(&self) -> Correction {
         Correction::none()
     }
-
-    fn written_frame_size(&self, num_pixels: usize) -> usize {
-        let mut buf = Vec::new();
-        let dummy_frame: Vec<Pixel> = (0..num_pixels)
-            .map(|_| Pixel { r: 0, g: 0, b: 0 })
-            .collect();
-        self.write_frame(&mut buf, dummy_frame.as_slice()).unwrap();
-        buf.len()
-    }
 }
 
 impl<T> Device for Box<T>
diff --git a/src/driver/mod.rs b/src/driver/mod.rs
index d15f9e3..b57fad5 100644
--- a/src/driver/mod.rs
+++ b/src/driver/mod.rs
@@ -40,7 +40,14 @@ impl fmt::Display for Error {
     }
 }
 
-impl error::Error for Error {}
+impl error::Error for Error {
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+        match &self {
+            Self::Io(err) => Some(err),
+            Self::Nix(err) => Some(err),
+        }
+    }
+}
 
 impl From<io::Error> for Error {
     fn from(err: io::Error) -> Self {