i2c: Factor our send() and recv() common logic

Most of the control flow logic between send and recv (error checking
etc) is the same. Factor this out into a common send_recv() API.
This is then usable by clients, where the control logic for send
and receive differs only by a boolean. E.g.

if (send)
   i2c_send(...):
else
   i2c_recv(...);

becomes:

i2c_send_recv(... , send);

Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@xilinx.com>
Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
Message-id: 1465833014-21982-4-git-send-email-fred.konrad@greensocs.com
Changes from FK:
  * Rebased on master.
  * Rebased on my i2c broadcast patch.
Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
Reviewed-by: Alistair Francis <alistair.francis@xilinx.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/i2c/core.c

@@ -149,36 +149,52 @@ void i2c_end_transfer(I2CBus *bus)
     bus->broadcast = false;
 }
 
-int i2c_send(I2CBus *bus, uint8_t data)
+int i2c_send_recv(I2CBus *bus, uint8_t *data, bool send)
 {
     I2CSlaveClass *sc;
     I2CNode *node;
     int ret = 0;
 
-    QLIST_FOREACH(node, &bus->current_devs, next) {
-        sc = I2C_SLAVE_GET_CLASS(node->elt);
-        if (sc->send) {
-            ret = ret || sc->send(node->elt, data);
-        } else {
-            ret = -1;
+    if (send) {
+        QLIST_FOREACH(node, &bus->current_devs, next) {
+            sc = I2C_SLAVE_GET_CLASS(node->elt);
+            if (sc->send) {
+                ret = ret || sc->send(node->elt, *data);
+            } else {
+                ret = -1;
+            }
+        }
+        return ret ? -1 : 0;
+    } else {
+        if ((QLIST_EMPTY(&bus->current_devs)) || (bus->broadcast)) {
+            return -1;
         }
+
+        sc = I2C_SLAVE_GET_CLASS(QLIST_FIRST(&bus->current_devs)->elt);
+        if (sc->recv) {
+            ret = sc->recv(QLIST_FIRST(&bus->current_devs)->elt);
+            if (ret < 0) {
+                return ret;
+            } else {
+                *data = ret;
+                return 0;
+            }
+        }
+        return -1;
     }
-    return ret ? -1 : 0;
 }
 
-int i2c_recv(I2CBus *bus)
+int i2c_send(I2CBus *bus, uint8_t data)
 {
-    I2CSlaveClass *sc;
+    return i2c_send_recv(bus, &data, true);
+}
 
-    if ((QLIST_EMPTY(&bus->current_devs)) || (bus->broadcast)) {
-        return -1;
-    }
+int i2c_recv(I2CBus *bus)
+{
+    uint8_t data;
+    int ret = i2c_send_recv(bus, &data, false);
 
-    sc = I2C_SLAVE_GET_CLASS(QLIST_FIRST(&bus->current_devs)->elt);
-    if (sc->recv) {
-        return sc->recv(QLIST_FIRST(&bus->current_devs)->elt);
-    }
-    return -1;
+    return ret < 0 ? ret : data;
 }
 
 void i2c_nack(I2CBus *bus)

include/hw/i2c/i2c.h

@@ -56,6 +56,7 @@ int i2c_bus_busy(I2CBus *bus);
 int i2c_start_transfer(I2CBus *bus, uint8_t address, int recv);
 void i2c_end_transfer(I2CBus *bus);
 void i2c_nack(I2CBus *bus);
+int i2c_send_recv(I2CBus *bus, uint8_t *data, bool send);
 int i2c_send(I2CBus *bus, uint8_t data);
 int i2c_recv(I2CBus *bus);