Refactor SMFI interface and ectool

tool/src/error.rs

@@ -1,11 +1,25 @@
+/// Errors returned by operations
 #[derive(Debug)]
 pub enum Error {
+    /// Data length is too large
+    DataLength(usize),
+    /// A parameter was invalid
     Parameter,
+    /// EC protocol returned an error result
     Protocol(u8),
+    /// EC protocol signature did not match
     Signature((u8, u8)),
+    /// Super I/O ID did not match
     SuperIoId(u16),
+    /// Blocking operation timed out
     Timeout,
+    /// Unexpected data from EC
     Verify,
+    /// EC protocol version is unsupported
+    Version(u8),
+    /// Indicates that a blocking operation would block
     WouldBlock,
+    /// Encountered a std::io::Error
+    #[cfg(feature = "std")]
+    Io(std::io::Error)
 }
-