Re: [PATCH 3/3] USB: driver for Freescale QUICC Engine USB Host Controller

[Sergei Shtylyov]

Hello.

David Brownell wrote:

> > > >  ... then the root hub emulation is completely pointless.

> > > It isn't. We always should emulate the root hub. The root hub
> > > is part and parcel of any USB Host. Even the one-port one.

> >   Hm, maybe that's what USB core thinks (because UHCI/OHCI/EHCI all 
> > have it) but e.g. MUSB doesn't have the root hub registers...

> Only the OHCI registers have bit positions matching what the USB
> spec says for hub status bits.

   Oh, didn't know that.

> Everything else, including musb_hdrc, has the relevant status encoded in other bits.

   Yes, but I thought that if there are no multiple ports, having the hub is 
just pointless.

> > I looked at the core and figured that USB core seems to use the root hub 
> > interface for port PM, etc. and expects it to bee present, so it seems 
> > unavoidable indeed... :-/

> Or more fundamentally:  for enumeration.  "Unavoidable" is correct.  ;)

   Not sure what you mean here but I guess having a root hub alows an uniform 
model of controlling the ports... anyway, USB specifies that it must be 
present in the host.

WBR, Sergei
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