bluetooth: Implement TxPower and RSSI of BluetoothAdvertisementData

content/common/bluetooth/bluetooth_device.h

Index: content/common/bluetooth/bluetooth_device.h
diff --git a/content/common/bluetooth/bluetooth_device.h b/content/common/bluetooth/bluetooth_device.h
index 73aef998b4bc768ac651ad62176062380a977147..575f43af1c796ed173cb0144f106fea81dce1222 100644
--- a/content/common/bluetooth/bluetooth_device.h
+++ b/content/common/bluetooth/bluetooth_device.h
@@ -20,6 +20,8 @@ struct CONTENT_EXPORT BluetoothDevice {
   BluetoothDevice();
   BluetoothDevice(const std::string& id,
                   const base::string16& name,
+                  int8_t tx_power,
+                  int8_t rssi,

[palmer, 2015/11/04 21:57:19]

Elsewhere in the code (in other code, e.g. device/bluetooth/bluetooth_device.h)
I see rssi declared as int and as int16. What is it really?

[ortuno, 2015/11/04 22:45:58]

According to the Bluetooth Spec RSSI and Tx Power are in fact int8 values. The
low level controller, BlueZ, stores these as int8 [1], but sends a int16 because
DBUS doesn't support int8 [2]. So in theory we should never see a value greater
than 127 or smaller than -128. We know that these are int8 values but just in
case we have a function to make sure the values passed by bluez are within the
int8 limit.

[1] http://git.kernel.org/cgit/bluetooth/bluez.git/tree/src/device.c#n265
[2] http://dbus.freedesktop.org/doc/api/html/group__DBusProtocol.html 

                   uint32 device_class,
                   device::BluetoothDevice::VendorIDSource vendor_id_source,
                   uint16 vendor_id,
@@ -31,9 +33,18 @@ struct CONTENT_EXPORT BluetoothDevice {
 
   static std::vector<std::string> UUIDsFromBluetoothUUIDs(
       const device::BluetoothDevice::UUIDList& uuid_list);
+  // 127 is used as Unknown Power. According to the Bluetooth spec valid powers
+  // are between [-127, 127]. Anything outside this range will be considered
+  // Unknown Power.
+  static int8_t ValidatePower(int16_t power);

[palmer, 2015/11/04 21:57:19]

So sometimes you have to take in larger ints, but really they are int8s?

[ortuno, 2015/11/04 22:45:58]

As mentioned above. This is just in case. In theory we should never receive
values outise the int8 range.

+  // TODO(ortuno): RSSI Unknown and Tx Power Unknown should have different
+  // values. Add kUnknownTxPower when implemented: http://crbug.com/551572
+  const static int8_t kUnknownPower = 127;
 
   std::string id;
   base::string16 name;
+  int8_t tx_power;
+  int8_t rssi;
   uint32 device_class;
   device::BluetoothDevice::VendorIDSource vendor_id_source;
   uint16 vendor_id;