On Tue, 20 Oct 2015, Mark Brown wrote:

On Tue, Oct 20, 2015 at 10:40:03AM -0400, Alan Stern wrote:

quoted

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.

Alan Stern