Add ReqResp Protocol

A simple protocol for request-response transactions

Author: lmbollen

clash-protocols.cabal

@@ -179,6 +179,7 @@ library
     Protocols.Internal.Units.TH
     Protocols.Plugin
     Protocols.Plugin.Internal
+    Protocols.ReqResp
     Protocols.Wishbone
     Protocols.Wishbone.Standard
     Protocols.Wishbone.Standard.Hedgehog

src/Protocols/ReqResp.hs

@@ -0,0 +1,53 @@
+{- |
+Simplest possible protocol for request-response communication.
+
+The forward channel channel has type @Signal dom (Maybe req)@ and is used to send requests.
+The backward channel has type @Signal dom (Maybe resp)@ and is used to send responses.
+
+The protocol must obey the following rules:
+* When the forward channel is @Just a@, it must not change until the transaction is completed.
+* The forward channel can not depend on the backward channel.
+* When the forward channel is @Nothing@, the backward channel may be undefined.
+
+This protocol can not be pipelined, for pipelined request-response communication see `Protocols.BiDf`.
+-}
+module Protocols.ReqResp where
+
+import qualified Clash.Prelude as C
+import Data.Kind (Type)
+import Protocols
+import Protocols.Internal.Classes
+import Prelude as P
+
+{- |
+Simplest possible protocol for request-response communication.
+
+The forward channel channel has type @Signal dom (Maybe req)@ and is used to send requests.
+The backward channel has type @Signal dom (Maybe resp)@ and is used to send responses.
+
+The protocol must obey the following rules:
+* When the forward channel is @Just a@, it must not change until the transaction is completed.
+* The forward channel can not depend on the backward channel.
+* When the forward channel is @Nothing@, the backward channel may be undefined.
+-}
+data ReqResp (dom :: C.Domain) (req :: Type) (resp :: Type)
+
+instance Protocol (ReqResp dom req resp) where
+  -- \| Forward channel for ReqResp protocol:
+  type Fwd (ReqResp dom req resp) = C.Signal dom (Maybe req)
+
+  -- \| Backward channel for ReqResp protocol:
+  type Bwd (ReqResp dom req resp) = C.Signal dom (Maybe resp)
+
+instance IdleCircuit (ReqResp dom req resp) where
+  idleFwd _ = pure Nothing
+  idleBwd _ = pure Nothing
+
+{- | Force a @Nothing@ on the backward channel and @Nothing@ on the forward
+channel if reset is asserted.
+-}
+forceResetSanity ::
+  forall dom req resp.
+  (C.HiddenReset dom) =>
+  Circuit (ReqResp dom req resp) (ReqResp dom req resp)
+forceResetSanity = forceResetSanityGeneric