Re: [GIT PULL] On-demand device probing

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Tue, 20 Oct 2015, Tomeu Vizoso wrote:

> On 20 October 2015 at 18:04, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Tue, 20 Oct 2015, Mark Brown wrote:
> >
> >> On Tue, Oct 20, 2015 at 10:40:03AM -0400, Alan Stern wrote:
> >>
> >> > Furthermore, that applies only to devices that use synchronous suspend.
> >> > Async suspend is becoming common, and there the only restrictions are
> >> > parent-child relations plus whatever explicit requirements that drivers
> >> > impose by calling device_pm_wait_for_dev().
> >>
> >> Hrm, this is the first I'd noticed that feature though I see the initial
> >> commit dates from January.
> >
> > Async suspend and device_pm_wait_for_dev() were added in January 2010,
> > not 2015!
> >
> >>  It looks like most of the users are PCs at
> >> the minute but we should be using it more widely for embedded things,
> >> there's definitely some cases I'm aware of where it will allow us to
> >> remove some open coding.
> >>
> >> It does seem like we want to be feeding dependency information we
> >> discover for probing way into the suspend dependencies...
> >
> > Rafael has been thinking about a way to do this systematically.
> > Nothing concrete has emerged yet.
> 
> This iteration of the series would make this quite easy, as
> dependencies are calculated before probes are attempted:
> 
> https://lkml.org/lkml/2015/6/17/311

But what Rafael is proposing is quite general; it would apply to _all_
dependencies as opposed to just those present in DT drivers or those 
affecting platform_devices.

Alan Stern

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