Messages in this thread | | | Date | Thu, 13 Oct 2011 12:04:25 -0400 (EDT) | From | Alan Stern <> | Subject | Re: [PATCH 2/5] drivercore: Add driver probe deferral mechanism |
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On Thu, 13 Oct 2011, Ming Lei wrote:
> Hi, > > On Thu, Oct 13, 2011 at 10:31 PM, Alan Stern <stern@rowland.harvard.edu> > >> Maybe we should understand the correct model of the ordering constraints > >> for the multiple device dependancies first, could you give a description or > >> some examples about it? > > > > The requirement is that devices must be capable of resuming in the > > order given by dpm_list, and they must be capable of suspending in > > the reverse order. > > > > Therefore if device A can't work unless device B is functional, then B > > must come before A in dpm_list. > > If all devices can support async suspend and resume correctly, looks like > the device order given by dpm_list is not needed any longer, doesn't it?
It _is_ needed, because the user can disable async suspend/resume via /sys/power/pm_async.
Also, not all devices do support async suspend/resume.
Alan Stern
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