Re: Planning Gnome Scan Inclusion

[David Zeuthen <david fubar dk>]

On Fri, 2006-09-08 at 14:54 +0200, �ienne Bersac wrote:
> Hello all !
> 
> Since march, i'm designing and developping a Gnome Scan infrastructure.
> See http://home.gna.org/gnomescan/index and Google "gnome scan" search
> result in general. I've been sponsored by Google do work on this project
> this summer. Mentored by Vincent Untz.

This looks like great stuff!

>               * hal scanner support
>               * dbus service

Suggest to just use a HAL addon for the D-BUS service, it's designed to
do exactly this kind of thing. 

It basically solves all the life cycle issues for you (e.g. no need to
start the service when the hardware is not there, creates several
instances of the daemon if you got several pieces of hardware, none if
you don't have the hardware, hotplug aware etc. etc.) and integrates
nicely into the HAL architecture, e.g. the addon will just provide some
org.freedesktop.Hal.Device.Scanner interface where you get to handle
method calls and emit signals. Much like a standard D-BUS service, only
without the (hard) issues of managing life cycles.

Using HAL addon's is much preferred to the old-school way of providing a
user space daemon for driving hardware with user space drivers. The
old-school way normally starts the daemon in a init script which will
load it even if you don't have the hardware.

See also page 13 of

 http://people.freedesktop.org/~david/talks/dynamic-device-handling-OLS-2006.pdf

for some (brief) details of HAL addons. Just ask on
hal lists freedesktop org if you need help with this.

     David