Re: [RFC Add in_use attribute] Let the driver know if it's in use

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Thursday 23 April 2009, Michael Trimarchi wrote:
> Greg KH wrote:
> > On Tue, Apr 21, 2009 at 08:43:28AM +0200, Michael Trimarchi wrote:
> >   
> >>>>> Exactly, what are you trying to do that differs from
> >>>>> device_for_each_child()?
> >>>>>   
> >>>>>       
> >>>>>           
> >>>> Is device for each child use to visist the first level of the tree?
> >>>>     
> >>>>         
> >>> Have you tried it?
> >>>   
> >>>       
> >> No, I take a look at the code.
> >>
> >> int device_for_each_child(struct device *parent, void *data,
> >>                           int (*fn)(struct device *dev, void *data))
> >> {
> >>         struct klist_iter i;
> >>         struct device *child;
> >>         int error = 0;
> >>
> >>         klist_iter_init(&parent->p->klist_children, &i);
> >>
> >> I was thinking that the klist_children is the fist_level one children, 
> >> so each time
> >> a device is registerd it add the link to the parent.
> >>     
> >
> > Yes it does.
> >
> > But you have to start at some device, right?  So you don't need to
> > iterate over it, just go from there on down if needed.
> >   
> I start for a device, go down until I find a leaf or find that the 
> subtree is marked.
> Mark the leaf and go up and take the next node like the walk_tg_tree. 
> The difference is
> that I skip subtree if they are mark in_use.
> > So I don't see why this helper function is needed at all yet, shouldn't
> > we be doing the check within the normal suspend device walk of the tree?
> >   
> Sorry but here I need some help here. Where is the walk of the device 
> tree during suspend?

In drivers/base/power/main.c there are functions like dpm_suspend(), for one
example, that walk the device tree, but they do it in a simplified way, using a
list prepared specifically for this purpose (so the walk is in fact linear).

Thanks,
Rafael