Re: [linux-usb-devel] Re: hotplugging to deal with firmware download

[Greg KH <greg@kroah.com>]

On Mon, Jun 03, 2002 at 03:02:46PM -0700, David Brownell wrote:
> >I see no plan to do it with the present power management system.
> >The devices are simply assumed to switch from suspended to working
> >in kernel space. Suspended may mean off here.
> 
> Well, the usb device drivers _do_ need individual suspend()/resume()
> callbacks.  The "new device model" stuff exists in part to ensure
> that devices get those calls appropriately.
> 
> For example, suspending a bus-powered hub would need to morph into
> disconnecting the devices it could no longer power ... and in your
> case, suspending a network device that discards its firmware would
> also need to morph into a disconnect.

Exactly.  The drivers for devices that need firmware to be downloaded to
them, will properly disconnect and shutdown the device before the system
shuts down.  This enables them to be powered up from a clean state when
the power is resumed.

This is very different from the software suspend model that just blindly
freezes memory and hopes all hardware will work properly when power is
reapplied (not to take away from this lovely hack, but it does not work
for all types of hardware, but is quite useful for those types that it
does work on.)

thanks,

greg k-h

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