Re: [gpm] Re: Gnome 2.16 Module Proposal: GNOME Power Manager

[Stefan Seyfried <seife suse de>]

Hi,

Just some short annotations...

On Thu, Apr 13, 2006 at 08:06:55PM -0400, David Zeuthen wrote:

> In other words, once g-p-m is able to run when no-one is logged in (e.g.
> system-wide), we simply add a button
> 
>  [Make settings system-wide]
> 
> and the user authenticates; we write the settings to the default area of
> e.g. gconf. We can play other tricks to do this automatically if there
> is only one user on the system, only show this button if the user has
> certain privileges (group membership) etc. etc. 
> 
> If g-p-m relies on e.g. the powersave daemon there is no such guarantee
> because it also reads settings from /etc/foobar. Sure, the Powersave
> daemon may be changed to not do this but what's the point of the daemon
> then?

Well, it would not be too hard to tell the powersave daemon "write your
current configuration as systm wide default". It is not there yet, but
it could be added.

> actually real networking and all the corner cases that implies. Have you
> ever tried debugging a program that relies on two processes and IPC?
> It's much harder than if it's a single process.

Its doable. "But it is hard to do it right" is no excuse for an inferior
solution ;-)

> With what I'm proposing (enforce all policy in a single desktop session
> daemon) you have *zero* of these problems. All your code is in a single
> process, no IPC overhead neither in code complexity nor execution speed,
> native configuration system (gconf for GNOME, the KDE equivalent for
> KDE) is always available etc etc.

But you need the same daemon twice. Once for GNOME, once for KDE. That's
code duplication, i'd say.

> So if I'm an admin of a site with 2000 computers I simply use an LDAP
> backend for gconf; I tweak one little setting in my LDAP console and my
> changes to the default power management policy is pushed out. 

But not to the 1000 computers that run KDE. So what you really want is
a system wide daemon that uses a LDAP backend.
 
> That's one reason it's extremely important to have a single source for
> configuration.

> > The benefit: you don't need to do this in the daemon if there is no 
> > client which need this function. In case of KPowersave for example we do this 
> > in the client and also only if the user enable it and edit the, for the user 
> > specific, blacklist. 
> 
> ... and things like grepping process lists is a complete hack and not
> acceptable. Plastering blacklists into the picture is just another hack
> because the first hack didn't work. Do you disagree?

The problem is simply that you will always have some legacy applications
that do not know about DBUS, inhibitors etc. RealPlayer anyone?
But of course you can leave the blacklist part out of gnome-powersave if
this is the only problem ;-)
 
> The way this works with gnome-screensaver and gnome-power-manager is
> that we have inhibitor interfaces in on the D-BUS session bus. 
> 
> So if I'm the Nautilus file manager I can simply take a lock on the
> inhibitor interface on g-p-m when copying large files, see
> 
>  http://bugzilla.gnome.org/show_bug.cgi?id=334806
> 
> for details. Similar, if I'm the Totem movie player, I take a lock on
> the gnome-screensaver inhibitor interface to prevent the screen saver
> from starting. It's *that* simple. There's a couple of other interfaces
> planned like being able to do an action before suspend or hibernate (if
> I'm a word processor I want to quick-save etc.)

This is a good idea, but pretty orthogonal to the discussed question, or
do i understand this completely wrong?

> A think like the Powersave daemon does little more than enforce policy,
> in fact I'd argue that it only enforces policy.

it can enforce policy, but it does not have to. It depends on the
configuration. You can just allow everything for everyone, then the
client has to decide.

Btw. it might be that i misunderstand "enforcing policy" here, since i
am not a native english speaker.

I actually have a feeling that the powersave guys have seen much more
of g-p-m than the g-p-m guys have seen of powersave ;-)

So short,
-- 
Stefan Seyfried                  \ "I didn't want to write for pay. I
QA / R&D Team Mobile Devices      \ wanted to be paid for what I write."
SUSE LINUX Products GmbH, Nürnberg \                    -- Leonard Cohen