From: Marcel Holtmann <marcel@holtmann.org>
To: BlueZ users <bluez-users@lists.sourceforge.net>
In-Reply-To: <4655449F.2080000@movilok.com>
References: <4655449F.2080000@movilok.com>
Date: Thu, 24 May 2007 10:40:06 +0200
Message-Id: <1179996006.26519.15.camel@aeonflux.holtmann.net>
Mime-Version: 1.0
Subject: Re: [Bluez-users] Concurrent hcitool commands
Reply-To: BlueZ users <bluez-users@lists.sourceforge.net>
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Sender: bluez-users-bounces@lists.sourceforge.net
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Hi Juan Carlos,

> we are trying to use hcitool to retrieve some information about 
> several devices and we need to do it in parallel (several scripts 
> concurrently call "hcitool name XX:XX:XX:XX:XX" using the same local 
> device looking for the name of several remote devices).
> 
> Doing this we found that some responses received from different remote 
> devices were mixed, we obtained the same device name from two different 
> remote devices.
> 
> The following is a simple way to check this behaviour:
> ---------------------------------------------------------------
> [root@localhost~]# hcitool -i hci0 name 00:12:D1:DB:9A:E3
> Nokia E70
> [root@localhost~]# hcitool -i hci0 name 00:13:FD:FC:DE:50
> Nokia 6680
> [root@localhost~]# hcitool -i hci0 name 00:12:D1:DB:9A:E3 & hcitool -i 
> hci0 name 00:13:FD:FC:DE:50
> [1] 14223
> Nokia E70
> Nokia E70
> [1]+  Done                    hcitool -i hci0 name 00:12:D1:DB:9A:E3
> ---------------------------------------------------------------
> 
> - The first command gets the right name of our E70 phone:
>  "Nokia E70"
> 
> - The second one also gets the right name of our 6680 phone:
>  "Nokia 6680"
> 
> - But if we invoke both commands concurrently, both "hcitool" calls get 
> the same name as the device response:
>  "Nokia E70"
>  "Nokia E70"
> 
> Are we doing something wrong?
> 
> Is there any technical limitation related to this kind of requests so we 
> must to do these calls serially?

this is a known limitation. And in general you can't execute name
request in parallel anyway. Every name request involves a baseband page
and that takes time and these can't be done in parallel. However some
chips create the illusion that they can.

I would advise you to use the D-Bus interface since it does the name
resolving in the background and automatically caches the resolved device
names for you. No need to fiddle around with low-level commands.

And in case of Bluetooth 2.1 devices with extended inquiry it will
deliver the remote name for free with the inquiry response. That all
works already and is completely hidden via D-Bus. So nothing for you to
worry about.

Regards

Marcel


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