Re: cdc-acm and remote wakeup

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On Tue, 27 Nov 2012, Oliver Neukum wrote:

> On Tuesday 27 November 2012 10:30:02 Alan Stern wrote:
> 
> > I disagree.  The usbfs interface is not as capable as the kernel's
> > internal API; that has always been true.  One of its limitations is the
> > inability to request remote wakeups.  We could add that to usbfs, but
> > for now it isn't there.
> 
> Yes.
>  
> > If that limitation means the buggy modem will crash whenever it is
> > being driven by a user program and the system suspends, so be it.  We
> 
> As far as the device is under control of usbfs that is a defensible viewpoint.
> 
> > shouldn't expect the kernel to work around hardware bugs when the
> > device in question isn't even under the control of a kernel driver.
> 
> That is not a position that is useful. In particular there's necessarily
> (if you use a modular kernel) a window where a device is configured
> due to the kernel's action, but not yet bound to a driver. We'd crash the
> device if we go to a system suspend then.

In fact, it would not crash.  Daniele said so; the crash occurs only 
when the modem is attached to a network.  If it hasn't been bound to a 
driver yet, it can't be attached.

>  That is no good and one more
> reason this must be handled in usbcore, not in cdc-acm.

Alan Stern

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