Re: [RFC] USB 3.0 Hub Changes

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On Wed, 21 Jul 2010, Sarah Sharp wrote:

> > It's not a big deal, so yes, it can wait.  Actually I think we should 
> > put the device into suspend, if we can, instead of putting the link 
> > into U1 or U2.  That would be pretty much equivalent to disabling the 
> > port anyway.
> 
> Using device suspend in that case is going to need special handling by
> the xHCI driver.  Normally, if a device is suspending, the xHCI host
> controller hardware wants to know about it.  The xHCI driver has to stop
> all the endpoints on the device with the "Suspend device" bit set.  Will
> the device already be deallocated by the time you try to suspend it?  Or
> will the struct usb_device still be around when the device is suspended?

Arggh!  Why does everything always turn out to be complicated?

No, the device structure won't already be deallocated.  In fact, it
might not even have been allocated in the first place.  One of the 
pathways leading to hub_port_disable() is when the memory allocation 
for the device structure fails.

However, if it is allocated then there probably aren't any endpoints 
running except ep0 -- if that helps.

Alan Stern

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