Re: [linux-pm] Re: The evilness of struct usb_device->auto_pm

Alan Stern <[email protected]>
Newsgroups gmane.linux.usb.devel
Message-ID <[email protected]>
On Fri, 28 Sep 2007, Rafael J. Wysocki wrote:

> > That's because the notifications go up the device tree, not down.  When 
> > a child is suspended, the parent is notified.  Then if the driver sees 
> > that all the children are suspended, the parent can be suspended as 
> > well.
> > 
> > Oliver has been trying to subvert this model by making usb-storage 
> > responsible for suspending the SCSI disk and CD/DVD drivers, which are 
> > located beneath it in the device tree.  I've been trying to convince 
> > him that the proper way to handle things is to let the SCSI drivers 
> > decide for themselves when their devices can be suspended, and then 
> > have them inform usb-storage.
> 
> Yes, I think that the SCSI layer should decide.
> 
> I guess that the SCSI layer is not really autosuspend-aware, is it?

Not yet.  I would like it to become autosuspend-aware.  Oliver wants to
avoid that by keeping all the awareness in usb-storage.  (But then what
about all the other SCSI host-adapter drivers?  Will they each have
their own way of deciding when a SCSI device can be suspended?)

Alan Stern


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