hw/i2c: move search to i2c_scan_bus method

Moves the search for matching devices on an i2c bus into a separate
method.  This allows for an object that owns an I2CBus can avoid
duplicating this method.

Tested: A BMC firmware was booted to userspace and i2c devices were
detected.

Signed-off-by: Patrick Venture <venture@google.com>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
Message-Id: <20210412194522.664594-4-venture@google.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

hw/i2c/core.c

@@ -77,6 +77,30 @@ int i2c_bus_busy(I2CBus *bus)
     return !QLIST_EMPTY(&bus->current_devs);
 }
 
+bool i2c_scan_bus(I2CBus *bus, uint8_t address, bool broadcast,
+                  I2CNodeList *current_devs)
+{
+    BusChild *kid;
+
+    QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
+        DeviceState *qdev = kid->child;
+        I2CSlave *candidate = I2C_SLAVE(qdev);
+        I2CSlaveClass *sc = I2C_SLAVE_GET_CLASS(candidate);
+
+        if (sc->match_and_add(candidate, address, broadcast, current_devs)) {
+            if (!broadcast) {
+                return true;
+            }
+        }
+    }
+
+    /*
+     * If broadcast was true, and the list was full or empty, return true. If
+     * broadcast was false, return false.
+     */
+    return broadcast;
+}
+
 /* TODO: Make this handle multiple masters.  */
 /*
  * Start or continue an i2c transaction.  When this is called for the
@@ -93,7 +117,6 @@ int i2c_bus_busy(I2CBus *bus)
  */
 int i2c_start_transfer(I2CBus *bus, uint8_t address, int recv)
 {
-    BusChild *kid;
     I2CSlaveClass *sc;
     I2CNode *node;
     bool bus_scanned = false;
@@ -115,17 +138,8 @@ int i2c_start_transfer(I2CBus *bus, uint8_t address, int recv)
      * terminating the previous transaction.
      */
     if (QLIST_EMPTY(&bus->current_devs)) {
-        QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
-            DeviceState *qdev = kid->child;
-            I2CSlave *candidate = I2C_SLAVE(qdev);
-            sc = I2C_SLAVE_GET_CLASS(candidate);
-            if (sc->match_and_add(candidate, address, bus->broadcast,
-                                  &bus->current_devs)) {
-                if (!bus->broadcast) {
-                    break;
-                }
-            }
-        }
+        /* Disregard whether devices were found. */
+        (void)i2c_scan_bus(bus, address, bus->broadcast, &bus->current_devs);
         bus_scanned = true;
     }
 

include/hw/i2c/i2c.h

@@ -87,6 +87,8 @@ void i2c_nack(I2CBus *bus);
 int i2c_send_recv(I2CBus *bus, uint8_t *data, bool send);
 int i2c_send(I2CBus *bus, uint8_t data);
 uint8_t i2c_recv(I2CBus *bus);
+bool i2c_scan_bus(I2CBus *bus, uint8_t address, bool broadcast,
+                  I2CNodeList *current_devs);
 
 /**
  * Create an I2C slave device on the heap.