[ohm] OHM vs. PPM

Rob Taylor rob.taylor at codethink.co.uk
Fri May 2 03:16:10 PDT 2008


Marcel Holtmann wrote:
> Hi Holger,
> 
>>>> OHM needs some work before its usable on a desktop system, mainly in 
>>>> that it should become a session daemon rather than a system daemon - 
>>>> connecting up to X from the system is not ideal.
>>> why? Leave it as system daemon and have an "agent" running in the X
>>> session that OHM can refer requests to. You might wanna check out on how
>>> BlueZ does it with PIN requests and mode change confirmations.
>> These two sentences are too short for getting a complete overview about
>> the BlueZ way of doing these things, but this sounds like what we already
>> had with the powersave daemon and kpowersave (the time kpowersave was only
>> a client for powersaved).
> 
> this needs a lot more explaining, but the beauty with the solution that
> BLueZ uses is that you don't need any extra well known names for the
> applet running in the user session. Even the actual object path is fully
> dynamic and then indeed allows to have multiple or stacked agents.
> 
> It works like this:
> 
> 	client creates object
> 	client call RegisterAgent(object) on the server
> 
> After that the server knows the unique name of the agent/client since it
> comes via the message. It also knows the object path of the clients
> objects. The only common factor is the interface definition to be used
> on that specific object. The server can also monitor the
> NameOwnerChanged signal to see if the client dies unexpected.
> 
> For all requests that need user interaction, the server can now call
> into the interface from the agent.
> 
> This gives the perfect system level versus user session separation
> without playing any dirty tricks or having static bus names or object
> paths.

That sounds like a very nice pattern, I'll keep it in mind.

Rob

> Regards
> 
> Marcel
> 
> 
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