From cf8e5838474ed1c6f9252ad0caa0f2773c7e0565 Mon Sep 17 00:00:00 2001
From: mwojcik <mw@m-labs.hk>
Date: Thu, 19 May 2022 15:54:05 +0800
Subject: [PATCH] comm_mgmt: expect error on config_read

---
 artiq/coredevice/comm_mgmt.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/artiq/coredevice/comm_mgmt.py b/artiq/coredevice/comm_mgmt.py
index 9833d7520..870e2759d 100644
--- a/artiq/coredevice/comm_mgmt.py
+++ b/artiq/coredevice/comm_mgmt.py
@@ -160,7 +160,12 @@ class CommMgmt:
     def config_read(self, key):
         self._write_header(Request.ConfigRead)
         self._write_string(key)
-        self._read_expect(Reply.ConfigData)
+        ty = self._read_header()
+        if ty == Reply.Error:
+            raise IOError("Device failed to read config. The key may not exist.")
+        elif ty != Reply.ConfigData:
+            raise IOError("Incorrect reply from device: {} (expected {})".
+                          format(ty, Reply.ConfigData))
         return self._read_string()
 
     def config_write(self, key, value):