On Fri, 1 Jul 2005, Duncan Sands wrote:

> > > but do we want to guarantee that the altsetting is always zero
> > > when probe is called (likewise for configuration)?  After all, drivers
> > > can be responsible for setting the values they want.
> > 
> > I think we do.  Drivers should find their devices initially in the 
> > default state.  That's why we install altsetting 0 after each driver 
> > unbinds.
> 
> I guess the same goes for the configuration.

> If the configuration is reset to zero, is that guaranteed to reset the
> altsetting too?

?  You sound confused.

Configurations aren't changed as easily as altsettings.  They can't be 
changed at all by drivers, normally.  Remember, each configuration 
contains a set of interfaces, and drivers bind to interfaces.  Change the 
config and you've got a completely new set of interfaces, requiring a new 
set of driver bindings.

And in particular, config 0 is the "unconfigured" state.  A device in that 
state isn't able to carry out its normal functions.

Alan Stern



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