Messages in this thread | | | Date | Wed, 24 Sep 2008 23:17:55 +0400 | From | Sergei Shtylyov <> | Subject | Re: [PATCH 3/3] USB: driver for Freescale QUICC Engine USB Host Controller |
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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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