[ltp] initial state vs. state transitions

[Henrique de Moraes Holschuh]

On Mon, 29 Dec 2008, David Abrahams wrote:
> on Mon Dec 29 2008, Henrique de Moraes Holschuh <hmh-AT-hmh.eng.br> wrote:
> > On Mon, 29 Dec 2008, David Abrahams wrote:
> >> Does this setting of the initial state trigger acpi or pm state
> >> transition hooks?
> >
> > No, and it wouldn't help that much, for various reasons, the main one
> > being that it is hard to get this right, and applications would still
> > need to do special processing to request the first event, and to wait
> > for it before doing anything else.
> 
> I'm not sure what "applications" means in this context.  I'm talking
> about the sort of things that typically get installed in
> /etc/pm/power.d, /etc/acpi, and /etc/udev

Applications in this context means "something you wanted to do with a single
script, but now I am telling you you need at least two ;-)".

> [By the way, it's almost impossible for me to keep track of these
> different mechanisms, and they seem to be proliferating.  Is there
> somewhere a guide that ties them all together conceptually?]

Yes: HAL.   You can do all the ACPI and uevent processing in HAL, it listens
to both.

> >> My concern is that to say "put the system in state X when on battery
> >> power" seems t require installing a transition hook and... something
> >> else.  What, I am not sure.
> >
> > I personally go with initscripts, because I do like these things to be
> > tied to the system and acpid.  
> 
> Wow, yet another pathway.  I am familiar with initscripts but in my
> experience they usually start and stop server processes.  How would I
> use initscripts with power transitions, etc.?  Or are you suggesting
> that initscripts are just used to handle startup states?  Then what
> about transitions out of suspend/hibernate?  Should I really be
> installing *three* sets of hooks?

I use initscripts to handle startup states.  And yes, you may end up needing
the THREE sets of hooks you mentioned :(

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh