Input Devices (was: Re: [Xgl/Xegl] Input Devices )

[Waldo Bastian]

On Wednesday 27 July 2005 20:51, Jim Gettys wrote:
> > An open question seems to be wether DBUS would be a suitable IPC
> > mechanism for that. One of the proposals so far is to have the
> > configuration client open the device and pass it's file descriptor to the
> > X server (see
> > http://lists.freedesktop.org/archives/xorg/2004-August/002104.html ) DBUS
> > doesn't seem to provide that at the moment. If that's considered the way
> > to go then either fd-passing needs to be added to DBUS or a different IPC
> > solution would be needed.
>
> It probably is better to use DBUS, for much of it, though we'll have to
> figure out some way to send the file descriptor.  The issue here is that
> the current internals of the X server do no have the ability for the X
> server to become a client of another server (in this case, DBUS); it
> might deadlock.

Even though the X server would communicate with the dbus server, wouldn't, 
conceptually speaking, the X server still be the server in this case? The 
dbus connection would just be another connection for clients to connect to 
the xserver and send commands to the X server.

I can see deadlock potential if the X server was to make calls across DBUS and 
blocked waiting for a response, but I don't think there is a need for that. 
First of all, with a configuration client, the X server itself would not need 
to be making any calls. Second, if it would need to make a call it could make 
the call asynchronously and the response would come back later, pretty much 
like other incoming dbus calls.

All that is needed is a way to register a fd and have the X server activate a 
callback when something happens on that fd. Is that possible at the moment, 
or does that require reorganizing the X server internals first?

Cheers,
Waldo
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