[rfc] Activating Common Services

Thiago Macieira thiago at kde.org
Tue Jun 19 07:54:30 PDT 2007

Richard Hughes said:
> Yes, although if we can change HAL trivially (I think we can) then I
> guess it might be the "best" solution long term.

See below.

>> That's probably that should be handled on a case-by-case basis. Some
>> services should be activated on boot (like HAL!)
> HAL's not needed until NetworkManager starts, and NM is not needed until
> nm-applet is loaded. That's a trivial case, but you get the idea.

I think you're underestimating HAL's use. For instance, I have HAL on my
machine (and use it) and I don't have NetworkManager. Simple logic
dictates that HAL is needed even without NM.

But my point is: some applications may connect to the system bus and start
listening for HAL's signals, but never actually make a call to it until a
signal comes (think wildcard signal-matching rules). Since they don't, it
never gets activated and therefore no signal is emitted.

I don't know if HAL is meant to work like that. Right now, since it can't
be activated, the behaviour above is acceptable. Which means applications
may already be using it. If the HAL team wants to support activation, it
has to require that at least one call be made if the application wants to
receive signals.

That's a possibly behaviour-incompatible change that each team of any
existing service on the system bus that spontaneously emits signals has to
face. Actually, since at least one call is necessary to emit signals, you
can say that it no longer emits signals spontaneously.

Conclusion: this is going off-topic. HAL's auto-activation is a decision
that HAL developers have to take, taking into consideration that it may
break existing applications.

  Thiago Macieira  -  thiago (AT) macieira.info - thiago (AT) kde.org
    PGP/GPG: 0x6EF45358; fingerprint:
    E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358

More information about the dbus mailing list