bluetooth: Implement TxPower and RSSI of BluetoothAdvertisementData

content/common/bluetooth/bluetooth_device.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_COMMON_BLUETOOTH_BLUETOOTH_DEVICE_H_
 #define CONTENT_COMMON_BLUETOOTH_BLUETOOTH_DEVICE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
 #include "device/bluetooth/bluetooth_device.h"
 
 namespace content {
 
 // Data sent over IPC representing a Bluetooth device, corresponding to
 // blink::WebBluetoothDevice.
 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,
                   uint16 product_id,
                   uint16 product_version,
                   bool paired,
                   const std::vector<std::string>& uuids);
   ~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;
   uint16 product_id;
   uint16 product_version;
   bool paired;
   std::vector<std::string> uuids;  // 128bit UUIDs with dashes. 36 chars.
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_BLUETOOTH_BLUETOOTH_DEVICE_H_