Battery Service exposing device battery properties

Hi.

Adding the battery service into the bluez, requires exposing the battery array (may be more than one) to the users. The internal implementation can be fairly easy, adding a GSList of btd_battery_info structures to the btd_device. This btd_battery_info may look like this :

struct btd_battery_info {
	uint8_t		namespace;
	uint16_t	description;
	uint8_t		level;
};

The batteries information should also be exposed using D-BUS interface. As this is a device property, which needs to be read when using the GetProperties D-BUS method, as well as be notified using the PropertyChanged signal from a device.

One logic way to display this information, is to add an array of object paths to the GetProperties dictionary, which will look like this :

    dict entry(
        string "Batteries"
        variant             array [
              object path "/org/bluez/14503/hci0/dev_3C_2D_B7_85_EC_C2/BATT01"
              object path "/org/bluez/14503/hci0/dev_3C_2D_B7_85_EC_C2/BATT02"
              object path "/org/bluez/14503/hci0/dev_3C_2D_B7_85_EC_C2/BATT03"
           ]
     )

This array represents the batteries in the system. A org.bluez.Battery interface will be added, including the function GetProperties. When you execute the GetProperties on a battery object path, you will get this :

   array [
      dict entry(
         string "NameSpace"
         variant             byte 1
      dict entry(
         string "Description"
         variant             uint16 44
      )
      dict entry(
         string "Level"
         variant             byte 94
      )
   ]

This will represent a single battery information element.

The problem here is with the PropertyChanged, which needs to include a String and a value. For that, we can do something like this :

signal sender=:1.558 -> dest=(null destination) serial=200 path=/org/bluez/14503/hci0/dev_3C_2D_B7_85_EC_C2/BATT02; interface=org.bluez.Battery; member=PropertyChanged
   array [
      dict entry(
         string "Level"
         variant byte 93
      )
   ]

However, having interfaces for each battery makes things complex, since you need to parse events on a new interface (org.bluez.Battery) and parse new object paths, and will need to figure out how to translate BATT01 into Battery with namespace/description. In addition, the PropertyChanged needs to be sent over org.bluez.Battery interface or org.bluez.Device interface.

What do you think ? How can I try and simplify this ?

Thanks,


Chen Ganir
Texas Instruments