[Bluez-users] clearing remote name cache

[Bluez-users] clearing remote name cache

[Emanuele Novelli]

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Hi using the hints about reading remote names from various threads I got on
this ML time ago I started experiments with D-Bus API for bluez.

I tried to read a remotename in a thread called from another thread who does
inquiry.
Each time he found a bdaddress he ask for a name
(snipped code)

msg = dbus_message_new_method_call("org.bluez", "/org/bluez/hci0", "
org.bluez.Adapter", "GetRemoteName");
dbus_message_append_args(msg, DBUS_TYPE_STRING,
&bdaddress,DBUS_TYPE_INVALID);
reply = dbus_connection_send_with_reply_and_block(conn, msg, -1, &err);
 if (reply == NULL) {
 printf("Error %s\n",err.message);

  }
 else {
 dbus_message_get_args(reply, NULL, DBUS_TYPE_STRING, &name,
DBUS_TYPE_INVALID);
                PBLOG_INFO("%s\n", name);
}

all works well till I change the name of the remote device (a phone). Each
time I run the program I still get the old name, no matter how can try.
Only workaround I got to solve this is to manually invoke hcitool name
<bdaddress> to change the actual name in cache.


P.S.
I'm rather new to dbus, but everywhere I read advices about dont using the
low level api but use an high level bindings (G-lib, Java, python) but most
of examples I found in bluez source codes use low leve apis, so I guess is
correct using that or not ?

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Re: [Bluez-users] clearing remote name cache

[Marcel Holtmann]

Hi Emanuele,

> Hi using the hints about reading remote names from various threads I
> got on this ML time ago I started experiments with D-Bus API for
> bluez.
> 
> I tried to read a remotename in a thread called from another thread
> who does inquiry. 
> Each time he found a bdaddress he ask for a name
> (snipped code)
> 
> msg = dbus_message_new_method_call("org.bluez", "/org/bluez/hci0",
> "org.bluez.Adapter", "GetRemoteName"); 
> dbus_message_append_args(msg, DBUS_TYPE_STRING,
> &bdaddress,DBUS_TYPE_INVALID);
> reply = dbus_connection_send_with_reply_and_block(conn, msg, -1,
> &err);
>  if (reply == NULL) {
>  printf("Error %s\n", err.message);
> 
>   }
>  else {
>  dbus_message_get_args(reply, NULL, DBUS_TYPE_STRING, &name,
> DBUS_TYPE_INVALID);
>                 PBLOG_INFO("%s\n", name);
> }
> 
> all works well till I change the name of the remote device (a phone).
> Each time I run the program I still get the old name, no matter how
> can try. 
> Only workaround I got to solve this is to manually invoke hcitool name
> <bdaddress> to change the actual name in cache.

the name resolving operation is an expensive operation. It always
involves a low-level baseband page. So we try to avoid these kind of
operation whenever possible. This means that we return the cached name
all the time. However the cache will be automatically updated when you
actually connect to the remote device or if extended inquiry (a new
Bluetooth 2.1 feature) is used.

Regards

Marcel



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Re: [Bluez-users] clearing remote name cache

[Emanuele Novelli]

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2007/3/27, Marcel Holtmann <marcel@holtmann.org>:
>
> Hi Emanuele,
>
> > Hi using the hints about reading remote names from various threads I
> > got on this ML time ago I started experiments with D-Bus API for
> > bluez.
> >
> > I tried to read a remotename in a thread called from another thread
> > who does inquiry.
> > Each time he found a bdaddress he ask for a name
> > (snipped code)
> >
> > msg = dbus_message_new_method_call("org.bluez", "/org/bluez/hci0",
> > "org.bluez.Adapter", "GetRemoteName");
> > dbus_message_append_args(msg, DBUS_TYPE_STRING,
> > &bdaddress,DBUS_TYPE_INVALID);
> > reply = dbus_connection_send_with_reply_and_block(conn, msg, -1,
> > &err);
> >  if (reply == NULL) {
> >  printf("Error %s\n", err.message);
> >
> >   }
> >  else {
> >  dbus_message_get_args(reply, NULL, DBUS_TYPE_STRING, &name,
> > DBUS_TYPE_INVALID);
> >                 PBLOG_INFO("%s\n", name);
> > }
> >
> > all works well till I change the name of the remote device (a phone).
> > Each time I run the program I still get the old name, no matter how
> > can try.
> > Only workaround I got to solve this is to manually invoke hcitool name
> > <bdaddress> to change the actual name in cache.
>
> the name resolving operation is an expensive operation. It always
> involves a low-level baseband page. So we try to avoid these kind of
> operation whenever possible. This means that we return the cached name
> all the time. However the cache will be automatically updated when you
> actually connect to the remote device or if extended inquiry (a new
> Bluetooth 2.1 feature) is used.


Ok thanks for  answer,  I'd like  more info about this.
 Are  2.1 compliance dongles already available on the market for end users?
And even if I'll got one of those I guess the remote devices should be
2.1too to answer to an extended inquiry.
What about the Bluez support about the new features of Bluetooth 2.1? (both
low level HCI api and D-bus)

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Re: [Bluez-users] clearing remote name cache

[Marcel Holtmann]

Hi Emanuele,

> Ok thanks for  answer,  I'd like  more info about this. 
>  Are  2.1 compliance dongles already available on the market for end
> users? 

no. However in most cases a firmware update for the BlueCore4 chips is
fully enough. So my guess is that Apple will update their built-in
dongles once the specification has been made public.

> And even if I'll got one of those I guess the remote devices should be
> 2.1 too to answer to an extended inquiry.

You need to have both sides support extended inquiry and the host stack
must set the new attributes to make this work. BlueZ is already doing
this if it finds a Bluetooth 2.1 dongle.

> What about the Bluez support about the new features of Bluetooth 2.1?
> (both low level HCI api and D-bus) 

The extended inquiry is fully support. For the D-Bus API you see
actually no difference since all this stuff is hidden. However it works
perfectly fine.

The support for simple pairing from Bluetooth 2.1 has not been published
and will only be published once the specification is public.

Regards

Marcel



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