start work on SD mock

Author: robamu

src/sdcard/mock.rs

@@ -0,0 +1,43 @@
+//! SD card mock module.
+
+/// SD card mock states.
+pub enum State {
+    /// Idle state.
+    Idle,
+    /// Ready state.
+    Ready,
+    /// Identification state.
+    Ident = 2,
+    /// Standby state.
+    Stby = 3,
+    /// Transfer state.
+    Tran = 4,
+    /// Data state.
+    Data = 5,
+    /// Receive state.
+    Rcv = 6,
+    /// Programming state.
+    Prg = 7,
+    /// Disconnected state.
+    Dis = 8,
+}
+
+/// SD card mock.
+pub struct SdCardMock {
+    state: State,
+}
+
+impl SdCardMock {
+    /// Create a new SD card mock in the idle state.
+    pub fn new() -> Self {
+        Self { state: State::Idle }
+    }
+
+    /// Insert a command into the SD card.
+    pub fn insert_command(&mut self, cmd_id: super::CmdId, argument: u32) {
+        match cmd_id {
+            super::CmdId::CMD0_GoIdleState => self.state = State::Idle,
+            _ => (),
+        }
+    }
+}

src/sdcard/mod.rs

@@ -34,6 +34,7 @@ pub mod cid;
 pub mod csd;
 pub mod response;
 pub mod spi;
+pub mod mock;
 
 /// The different types of card we support.
 #[cfg_attr(feature = "defmt-log", derive(defmt::Format))]