hal draft spec

Dave Malcolm david at davemalcolm.demon.co.uk
Sun Sep 14 18:09:34 EEST 2003

On Sat, 2003-09-13 at 12:36, David Zeuthen wrote:
> On Fri, 2003-09-12 at 19:13, Dave Malcolm wrote:
> > A thought on the proposal:
> > 
> > Flat vs hierarchical
> > --------------------
> > Currently there is a single list of all devices attached to the system. 
> > Perhaps devices should form a hierarchy: 
> > 	- a connectivity hierarchy, with a "root" device representing the
> > motherboard, with CPU and memory attached, and buses coming off it etc
> > 	- a category hierarchy: with "All devices" at the root, with
> > subcategories such as "Storage Devices", "Joysticks" etc
> > 
> This is how WinXP does it. AFAIK they even map the USB topology with
> hubs correctly which is a nice little detail.

Yes; that would be great to support; it was what I had in mind, although
somehow it didn't make it into my email :-)

> > Rather than querying all devices and have device added/removed
> > messages,  you query for the root device, query the children of a
> > device, and get child added/removed messages for a particular node in
> > the hierarchy.
> > 
> > The category hierarchy could be generated from the physical hierarchy
> > inside libhal.
> > 
> Yes - both are just views of different topologies. But we should
> definately have tree-iterators in libhal for different views at some 
> point.
> > Or is this just an unnecessary complication?
> > 
> I guess one way to do it would be to introduce a PhysicalParent property
> of a device that hal_hotplug (though inspection using libhal) would compute
> and set. That would of cource require representation of virtual hubs as
> Device objects, but maybe that is not a big problem. Maybe it would even
> make sense.

> Btw, let me use this opportunity to announce that I have published a
> modified HTML-version of the spec. I hope to have a final version 0.1 of
> the spec available soon (no earlier than late next week unfortunatly) so
> I can get back to coding. Comments are welcome.

It looks like you're doing the spec in DocBook, from which you're
generating the HTML.  Please can you add the DocBook source to the
website as well!  (preferably XML rather than SGML)  That way we can
post patches for the spec to this list.

> The URL for the project page is http://pdx.freedesktop.org/~hal/
> Regards,
> David

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