Re: Non-enumerable devices on USB and other enumerable buses

[Alan Stern]

On Wed, 14 Aug 2013, Mark Brown wrote:

> On Wed, Aug 14, 2013 at 10:27:26AM -0400, Alan Stern wrote:
> > On Wed, 14 Aug 2013, Mark Brown wrote:
> 
> > > I'd expect that we're just looking at hooks around connection and
> > > disconnection here here - if we're looking at much more it seems like we
> > > must be doing something wrong.
> 
> > Connection and disconnection of what?
> 
> The device on the bus.
> 
> > In the example mentioned earlier, the GPIOs to power an on-board USB
> > hub would have to be initialized when the host controller was started.  
> > You wouldn't want to wait for the on-board hub to be detected, because
> > without those GPIOs set properly, it never would be discovered on the
> > USB bus.  Right?
> 
> Yes, so you'd want callbacks when the device actually appears and
> disappears.

No, no -- this is exactly the point I was trying to make.  The on-board
hub _won't_ appear on the USB bus until the GPIOs are set.  Therefore
the callback to set the GPIOs needs to be at a different place, not
when the device appears.

> > Perhaps the platform-level code would need to hook into the places
> > where the discoverable bus is registered and unregistered.
> 
> We'd need some way to get information to the drivers still, and to
> handle drivers that want to stop and start things.

Um...  What exactly does this mean?  It's so generic, it could apply to
anything under drivers/.  After all, what driver doesn't want to stop
and start things?

Alan Stern

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