Re: [Bluez-devel] Cached friendly names never updated when changed

[Pierre-Yves Paulus <py@idlum.be>]

Hi Marcel,

Thanks for your fast answer.

>> It seems that once a friendly name has been cached to /var/lib/ 
>> bluetooth/*/names, RemoteNameUpdated signals contain this cached  
>> name forever, and user is never informed of a name change unless  
>> those "names" files are deleted.
> 
> the names are never updated once retrieved. At least not via an  
> inquiry run. If you connect to a remote device, it will update the  
> name. Another option is Extended Inquiry support if you have the  
> hardware for it.
> 
> The reason behind this is that the remote name operation is too  
> expensive if you don't have an ACL link between two devices. And a lot  
> of times the name doesn't change so often or it is unimportant anyway.

It makes a lot of sense, at least for the python example I submitted, 
which was only performing calls to "DiscoverDevices".

But I've encountered another situation, where bluez' caching behaviour 
produces some nonsense. I have no simple test application to provide, 
but it is quite simple to explain and understand.

I've an application which performs a continuous inquiry (eg when it gets 
DiscoveryCompleted, it calls DiscoverDevices() and so on). In the 
meantime, this application does also perform sdp extraction and rfcomm 
connections to the detected devices. Here is a record of all 
RemoteNameUpdated signals from a particular device:

I delete /var/lib/bluetooth/*/names, set my device's name to "Name 1", 
and start my application

RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1

So far so good. At this point I set my device's name to "Name2": I start 
to get mixed values (I understand that "Name1" are sent out from the 
discovery, and thus use the cached value as you explainded above, and 
"Name2" are from the other operations, which are actually getting the 
current name, because they do connect to the device)

RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name1
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name1

At this point I delete /var/lib/bluetooth/*/names. As cache is recreated 
with the current value (Name2) everything looks good again

RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2

At this point, I change my device's name to "Name3". Things get mixed up 
again.

RemoteNameUpdated signal received: 006057BB4D92 - Name3
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name3
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name3
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name2
RemoteNameUpdated signal received: 006057BB4D92 - Name3
RemoteNameUpdated signal received: 006057BB4D92 - Name2

So, shouldn't the cached value get updated when bluez gets a different 
name later on?

Best Regards,
Pierre-Yves

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