hw/i2c: add match method for device search

At the start of an i2c transaction, the i2c bus searches its list of
children to identify which devices correspond to the address (or
broadcast).  Now the I2CSlave device has a method "match" that
encapsulates the lookup behavior. This allows the behavior to be changed
to support devices, such as i2c muxes.

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: <20210412194522.664594-3-venture@google.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

2 files changed, 30 insertions, 4 deletions

diff --git a/hw/i2c/core.c b/hw/i2c/core.c
index 21ec52ac5a..d03b0eea5c 100644
--- a/hw/i2c/core.c
+++ b/hw/i2c/core.c
@@ -118,10 +118,9 @@ int i2c_start_transfer(I2CBus *bus, uint8_t address, int recv)
         QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
             DeviceState *qdev = kid->child;
             I2CSlave *candidate = I2C_SLAVE(qdev);
-            if ((candidate->address == address) || (bus->broadcast)) {
-                node = g_malloc(sizeof(struct I2CNode));
-                node->elt = candidate;
-                QLIST_INSERT_HEAD(&bus->current_devs, node, next);
+            sc = I2C_SLAVE_GET_CLASS(candidate);
+            if (sc->match_and_add(candidate, address, bus->broadcast,
+                                  &bus->current_devs)) {
                 if (!bus->broadcast) {
                     break;
                 }
@@ -290,12 +289,28 @@ I2CSlave *i2c_slave_create_simple(I2CBus *bus, const char *name, uint8_t addr)
     return dev;
 }
 
+static bool i2c_slave_match(I2CSlave *candidate, uint8_t address,
+                            bool broadcast, I2CNodeList *current_devs)
+{
+    if ((candidate->address == address) || (broadcast)) {
+        I2CNode *node = g_malloc(sizeof(struct I2CNode));
+        node->elt = candidate;
+        QLIST_INSERT_HEAD(current_devs, node, next);
+        return true;
+    }
+
+    /* Not found and not broadcast. */
+    return false;
+}
+
 static void i2c_slave_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *k = DEVICE_CLASS(klass);
+    I2CSlaveClass *sc = I2C_SLAVE_CLASS(klass);
     set_bit(DEVICE_CATEGORY_MISC, k->categories);
     k->bus_type = TYPE_I2C_BUS;
     device_class_set_props(k, i2c_props);
+    sc->match_and_add = i2c_slave_match;
 }
 
 static const TypeInfo i2c_slave_type_info = {
diff --git a/include/hw/i2c/i2c.h b/include/hw/i2c/i2c.h
index 1f7c268c86..9b8b95ff4a 100644
--- a/include/hw/i2c/i2c.h
+++ b/include/hw/i2c/i2c.h
@@ -16,6 +16,7 @@ enum i2c_event {
     I2C_NACK /* Masker NACKed a receive byte.  */
 };
 
+typedef struct I2CNodeList I2CNodeList;
 
 #define TYPE_I2C_SLAVE "i2c-slave"
 OBJECT_DECLARE_TYPE(I2CSlave, I2CSlaveClass,
@@ -39,6 +40,16 @@ struct I2CSlaveClass {
      * return code is not used and should be zero.
      */
     int (*event)(I2CSlave *s, enum i2c_event event);
+
+    /*
+     * Check if this device matches the address provided.  Returns bool of
+     * true if it matches (or broadcast), and updates the device list, false
+     * otherwise.
+     *
+     * If broadcast is true, match should add the device and return true.
+     */
+    bool (*match_and_add)(I2CSlave *candidate, uint8_t address, bool broadcast,
+                          I2CNodeList *current_devs);
 };
 
 struct I2CSlave {