Re: [PATCH v4 01/10] Battery: Add Battery Service Gatt Client

Hi Chen,

On Thu, Aug 16, 2012, Chen Ganir wrote:

quoted

quoted

However, i fail to understand why the object manager prevents this
from getting accepted - do you have a time estimation when the
object manager should be active or available ?

By the time of our next release (as per the content under the BlueZ 5
section in our TODO file).

Is there anywhere some documentation or instructions how to adapt
the API for the new object manager ? Is it backward compatible to
what we have today ? Do we really hold back DBUS additions until we
change the DBUS API ?

As an unrelated thing (but since I saw it in your commit messages too):
please spell D-Bus as D-Bus, not DBUS, DBus, or anything else in natural
written language. This keeps it consistent with the rest of our
documentation as well as how the D-Bus project itself spells the name.

Regarding the Object Manager interface the implementation details you'd
get from Lucas and Luiz who are working on it whereas the API spec is
available here:

http://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-objectmanager

quoted

quoted

I prefer this way of putting the batteries below the device, since it
is obvious which battery belongs to each device.

I fully agree with this. It's not what I had an issue with. However, if
we really want to make this clear you could additionally have a "Device"
property for each battery object pointing back to the parent object.

I can do that, if it helps. Although it is not necessary, since the
object path for a battery already contains the device objec path in
it :
[variable prefix]/{hci0,..}/dev_XX_XX_XX_XX_XX_XX/BATT-NN-DDDD
Adding a device object path as a property will be redundant.

Even though we do have such a hierarchical construction of the paths I
don't think we should encourage this kind of magic tricks in trying look
into actual values of object paths to infer their relation to each
other. However, since the battery object paths would be discovered
through the device object there might not be any need for such a
backwards reference.

quoted

quoted

The other option i can think of is to have another interface
registered on the device object path:

Service		org.bluez
Interface	org.bluez.Batteries
Object path	[variable prefix]/{hci0,..}/dev_XX_XX_XX_XX_XX_XX

Methods	dict GetProperties()

	Returns all properties for the interface. See the
	Properties section for the available properties.

Signals		ProperyChanged(string name, variant value)

	This signal indicates a changed value of the given
	property.

Properties	array{object} Batteries [readonly]

	List of device battery object paths that represents the available
batteries on the remote devices.


Service		org.bluez
Interface	org.bluez.Battery
Object path	[variable prefix]/{hci0,..}/dev_XX_XX_XX_XX_XX_XX/BATT-NN-DDDD


Methods	dict GetProperties()

	Returns all properties for the interface. See the
	Properties section for the available properties.

Signals		PropertyChanged(string name, variant value)

	This signal indicates a changed value of the given
	property.

Properties	byte Level [readonly]

		Battery level (0-100).

Any other suggestion ?

That would work, although both of these interfaces are rather
light-weight in that they only contain a single property which begs the
question whether this is a bit over-kill.

I know. I believe so as well, but if you want to separate the
interfaces, it is a must.

quoted

Another option is to do away with the per-battery object somehow and
expose all batteries through a single interface. I'm not so sure that's
a good idea though since it could prevent future extensibility of the
API and doesn't reuse the common tools we have for object-like
abstractions (which a battery certainly is).

If we do what you suggest, a battery name (namespace+descriptor)
will be the property name, and the value should be the battery
level. i'm not too comfortable with it, and it is different than
what we used to do up until now.

So where do we go from here ?

Some extra opinions/view points could help. Maybe Marcel or Luiz have
some preferences/ideas on how to do this.

Johan