From 080752092c484ef373edbf2912b31308f3e24970 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Sat, 26 Dec 2015 22:43:28 +0800
Subject: [PATCH] gateware/rtio: add LogChannel

---
 artiq/gateware/rtio/__init__.py |  2 +-
 artiq/gateware/rtio/core.py     | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/artiq/gateware/rtio/__init__.py b/artiq/gateware/rtio/__init__.py
index 9f37a2c32..88ef7fb57 100644
--- a/artiq/gateware/rtio/__init__.py
+++ b/artiq/gateware/rtio/__init__.py
@@ -1,3 +1,3 @@
-from artiq.gateware.rtio.core import Channel, RTIO
+from artiq.gateware.rtio.core import Channel, LogChannel, RTIO
 from artiq.gateware.rtio.analyzer import Analyzer
 from artiq.gateware.rtio.moninj import MonInj
diff --git a/artiq/gateware/rtio/core.py b/artiq/gateware/rtio/core.py
index 94e250c62..e258b2a04 100644
--- a/artiq/gateware/rtio/core.py
+++ b/artiq/gateware/rtio/core.py
@@ -310,6 +310,15 @@ class Channel:
         return cls(phy.rtlink, probes, overrides, **kwargs)
 
 
+class LogChannel:
+    """A degenerate channel used to log messages into the analyzer."""
+    def __init__(self):
+        self.interface = rtlink.Interface(
+            rtlink.OInterface(32, suppress_nop=False))
+        self.probes = []
+        self.overrides = []
+
+
 class _KernelCSRs(AutoCSR):
     def __init__(self, chan_sel_width,
                  data_width, address_width, full_ts_width):
@@ -385,6 +394,12 @@ class RTIO(Module):
         o_statuses, i_statuses = [], []
         sel = self.kcsrs.chan_sel.storage
         for n, channel in enumerate(channels):
+            if isinstance(channel, LogChannel):
+                i_datas.append(0)
+                i_timestamps.append(0)
+                i_statuses.append(0)
+                continue
+
             selected = Signal()
             self.comb += selected.eq(sel == n)