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.
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