tpm: drop cmd from Emulator struct

The command is not done asynchronously. And there is no way to propagate
this error anywhere.

Signed-off-by: Wei Liu <liuwe@microsoft.com>

tpm/src/emulator.rs

@@ -72,7 +72,6 @@ pub struct BackendCmd {
 }
 
 pub struct Emulator {
-    cmd: Option<BackendCmd>,
     caps: PtmCap, /* capabilities of the TPM */
     control_socket: SocketDev,
     data_fd: RawFd,
@@ -100,7 +99,6 @@ impl Emulator {
         })?;
 
         let mut emulator = Self {
-            cmd: None,
             caps: 0,
             control_socket: socket,
             data_fd: -1,
@@ -287,13 +285,12 @@ impl Emulator {
     }
 
     /// Function to write to data socket and read the response from it
-    fn unix_tx_bufs(&mut self) -> Result<()> {
+    fn unix_tx_bufs(&mut self, cmd: &mut BackendCmd) -> Result<()> {
         let isselftest: bool;
         // SAFETY: type "sockaddr_storage" is valid with an all-zero byte-pattern value
         let mut addr: sockaddr_storage = unsafe { mem::zeroed() };
         let mut len = mem::size_of::<sockaddr_storage>() as socklen_t;
 
-        if let Some(ref mut cmd) = self.cmd {
         cmd.selftest_done = false;
         isselftest = is_selftest(cmd.input.to_vec(), cmd.input_len);
 
@@ -362,34 +359,20 @@ impl Emulator {
             errcode.copy_from_slice(&cmd.output[6..6 + 4]);
             cmd.selftest_done = u32::from_ne_bytes(errcode).to_be() == 0;
         }
-        }
 
         Ok(())
     }
 
-    pub fn deliver_request(&mut self, in_cmd: &mut BackendCmd) -> Result<Vec<u8>> {
+    pub fn deliver_request(&mut self, cmd: &mut BackendCmd) -> Result<Vec<u8>> {
-        if self.cmd.is_some() {
+        self.unix_tx_bufs(cmd)?;
-            //previous request did not finish cleanly
-            return Err(Error::DeliverRequest(anyhow!(
-                "Cannot deliver tpm Request as previous cmd did not complete."
-            )));
-        }
-        self.cmd = Some(in_cmd.clone());
 
-        self.unix_tx_bufs()?;
+        let output = cmd.output.clone();
+        cmd.output.fill(0);
+        cmd.output.clone_from(&output);
 
-        let output = self.cmd.as_ref().unwrap().output.clone();
-        in_cmd.output.fill(0);
-        in_cmd.output.clone_from(&output);
-
-        self.backend_request_completed();
         Ok(output)
     }
 
-    pub fn backend_request_completed(&mut self) {
-        self.cmd = None;
-    }
-
     pub fn cancel_cmd(&mut self) -> Result<()> {
         let mut res: PtmResult = 0;