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From: Alan McKinnon <alan.mckinnon@gmail.com>
To: gentoo-user@lists.gentoo.org
Subject: Re: [gentoo-user] Re: New xorg.conf with x11-base/xorg-server-1.5.3-r5
Date: Sun, 17 May 2009 16:32:25 +0200
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On Sunday 17 May 2009 14:15:31 pk wrote:
> > But you have that in the current setup. Hal (for better or worse) is the
> > daemon. dbus is simply a message transport and can be omitted from the
> > conceptual diagram
>
> Why is dbus needed? Why can't the user space apps talk to the user space
> daemon directly? To me it's just another unnecessary layer, each layer
> needs some kind of translation and thus resources. To me hal or whatever
> may replace it should have a minimalist approach.
Because the methodology is not that user-space apps talk to hal, but that h=
al=20
sends events to user space apps that are listening. And hal does not and=20
should not know anything about those apps.
Polling vs events is a problem that was solved a very long time ago. For a=
=20
dynamically changing system, events wins hands down almost always (one majo=
r=20
exception - real time OSes). It's asynchronous, easier to program and both =
hal=20
and the user space app talk to one and only one well defined API, and just=
=20
forget all about timing issues.
=46rom an engineering point of view, a message bus is an excellent idea.
=2D-=20
alan dot mckinnon at gmail dot com