Re: Runtime PM for PCI-based USB host controllers

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On Tue, Jun 01, 2010 at 10:59:17AM -0400, Alan Stern wrote:

> Can we rely on the forbid/allow mechanism?  If userspace never allows 
> runtime suspend for devices like the video controller then there's no 
> problem.  Conversely, if a PCI device really doesn't have a driver and 
> isn't used for anything, then by default it should go into a lower 
> power state if userspace allows this.

I think that's safe, yes. Other fringe concerns include things like 
smbus controllers - we typically won't allow a driver to bind to them 
because they're used by ACPI, so putting the in D3 is also an error. So 
I think Rafael's right in that we should default to forbid unless a 
driver knows that it's safe, and let userspace override us.

-- 
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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