GattManager1 and multiple-controllers

GattManager1 and multiple-controllers

[Arman Uguray]

Hi,

We had some discussion about this on IRC but I thought I'd gather
everything into an email and keep the discussion going on the mailing
list.

The question I have was regarding how bluetoothd should behave as a
GATT server when there are multiple controllers on the system. The
main things to figure out here are:

   1. Should there be a single global gatt_db or should there be a
gatt_db instance per-adapter? holtmann@ suggested that the latter
makes the most sense, since the spec always appears to talk always
about a host that acts on a single controller. With a single GATT
database, we get into undefined territory when multiple controllers
want to access it; for instance, if a service wants to send a
notification will that cause all attached controllers to send out the
same notification? Seems a bit strange.

   2. If gatt_db is per-adapter, then should GattManager1 be a global
interface or should it be on the adapter object? Basically, what
happens when an external application registers a service? Do we want
it to automatically show up in the databases of all local adapters?
Should the application be able to say which adapter to use? What if
some of the adapters are single-mode BR/EDR-only adapters?

I personally think that exposing the GattManager1 interface on each
adapter object is the simplest approach but a lot of people seem to
have voiced opinions on this, hence it would be nice to discuss this
here and figure out what makes the most sense.

Thanks!
Arman

Re: GattManager1 and multiple-controllers

[Luiz Augusto von Dentz]

Hi Arman,

On Tue, Feb 10, 2015 at 1:25 AM, Arman Uguray <armansito@chromium.org> wrote:
> Hi,
>
> We had some discussion about this on IRC but I thought I'd gather
> everything into an email and keep the discussion going on the mailing
> list.
>
> The question I have was regarding how bluetoothd should behave as a
> GATT server when there are multiple controllers on the system. The
> main things to figure out here are:
>
>    1. Should there be a single global gatt_db or should there be a
> gatt_db instance per-adapter? holtmann@ suggested that the latter
> makes the most sense, since the spec always appears to talk always
> about a host that acts on a single controller. With a single GATT
> database, we get into undefined territory when multiple controllers
> want to access it; for instance, if a service wants to send a
> notification will that cause all attached controllers to send out the
> same notification? Seems a bit strange.

Well you can only do notifications if you are connected, and we should
be tracking what device has enable them anyway.

>    2. If gatt_db is per-adapter, then should GattManager1 be a global
> interface or should it be on the adapter object? Basically, what
> happens when an external application registers a service? Do we want
> it to automatically show up in the databases of all local adapters?
> Should the application be able to say which adapter to use? What if
> some of the adapters are single-mode BR/EDR-only adapters?
>
> I personally think that exposing the GattManager1 interface on each
> adapter object is the simplest approach but a lot of people seem to
> have voiced opinions on this, hence it would be nice to discuss this
> here and figure out what makes the most sense.

It is probably the easiest to start with but I also agree with what
Johan said on irc, we can have a global one as well per adapter, which
makes sense to avoid having application to do extra lookups for
adapter. Anyway lets start with per adapter so we get things moving.


-- 
Luiz Augusto von Dentz