On Tue, Nov 12, 2013 at 10:49 AM, Claudio Takahasi
<claudio.takahasi@xxxxxxxxxxxxx> wrote:
> On Mon, Nov 11, 2013 at 3:56 PM, Scott James Remnant <keybuk@xxxxxxxxxx> wrote:
>> How will service changed be handled? How will BlueZ track the set of
>> applications, and the set of services etc. defined by those
>> applications in a manner that keeps handles consistent? How will it
>> handle generating the Services Changed notification in the cases where
>> the set of applications and/or services change, or the handles change?
>
> We implemented a hash of declarations. Using the "Id" provided in the
> options dictionary (see RegisterAgent) we are able to identity if the
> external service changed its attributes.
> However, I don' t think we will upstream this approach soon, Marcel
> wants a simpler approach: always send ServiceChanged.
>
While this is probably "spec sufficient", and probably sufficient for
passing qualification, I'm not sure that this is necessarily the best
approach since this means that BlueZ when acting as a GATT Server
wouldn't be behaving quite the same as, say, a commodity BTLE device.
>>> +Characteristic hierarchy
>>> +========================
>> :
>>> +Service org.bluez
>>> +Interface org.bluez.Characteristic1 [Experimental]
>>> +Object path [variable prefix]/{hci0,hci1,...}/dev_XX_XX_XX_XX_XX_XX/serviceXX/charYYYY
>>
>> This would also need a "Permissions" property akin to the one you have
>> for Descriptors - characteristics can be "not accessible", read-only,
>> write-only, read/write - and can also require authorization,
>> authentication, encryption and minimum encryption key sizes - as with
>> descriptors.
>
> It is implemented already, there is an optional "Flags" property :
> "array{string} Flags [read-only, optional]"
>
Flags seemed to correspond to the Flags characteristic descriptor and
not the simple permissions of the characteristic itself.
>>> + array{byte} Value [read-write]
>>> +
>>> + Cached Value of the characteristic. If present, the
>>> + value will be cached by bluetoothd and updated when the
>>> + PropertiesChanged signal is emitted.
>>> +
>>> + External services must emit this signal when the
>>> + characteristic supports notification/indication, so
>>> + that clients can be notified of the new value.
>>
>> The PropertiesChanged signal explains how Notification will be handled
>> - but how will Indication? How will a service receive the Indication
>> Confirmation from the remote devices?
>
> The bluetoothd core manages the Confirmation. In my opinion clients
> listening for PropertiesChanged don' t need to know the difference
> between notification and indication.
> Allow an external client to manage the Confirmation will insert
> additional complexity without giving real benefits.
>
I'm thinking of the opposite way around - not the clients, but the services.
If I implement a service over the D-Bus API, and a characteristic
supports Indication, then is it not important that the service be
informed when the clients confirm the Indication that is sent out?
Otherwise it makes Indications identical to Notifications when
implementing a service using the BlueZ D-Bus API, which may cause
issues with implementing certain profiles.
>>> +Application Agent hierarchy
>>> +===========================
>>> +
>>> +Service unique name
>>> +Interface org.bluez.ApplicationAgent1 [Experimental]
>>> +Object path freely definable
>>> +
>>
>> "Agent" seems unnnecessary here - if the object is an Application,
>> then org.bluez.Application1 would be a decent enough name. Thus an
>> "Application" consists of multiple Services, each of which consists of
>> multiple Characteristics, each of which has multiple Descriptors
>
> IMO "Agent" gives a better association with its functionality, it
> reminds me org.bluez.Agent1.
> Let's wait the opinion of the others developers...
>
I was more thinking that we have "AgentManager" -> "Agent",
"ProfileManager" -> "Profile", "ServiceManager" -> "Service" ... all
of those use the agent-style pattern, but only "Pairing" Agent is
called Agent.
But honestly, bike shedding ;-) I'm only complaining because calling
it "ApplicationAgent" would slightly screw up my naming convention
inside Chromium
Scott
--
Scott James Remnant | Chrome OS Systems | keybuk@xxxxxxxxxx | Google
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