> > That's why David and Roman's desire to share as much code as is
> > possible, practical and useful makes a lot of sense to me.
> > Of course, this presupposes that the hardware (UHCI, OHCI, EHCI)
> > allows for common behavior.
At some level, the "common behavior" is "USB support"!
> > If I understand correctly, this
> > isn't too much of a problem and the major differences between USB
> > host-controller types are only slight performance differences
> > (in the case of EHCI, I am referring to the backward compatibility
> > slow-speed mode). Is that correct?
>
> Mostly, yes.
In fact, an EHCI controller will usually be packaged with at least
one "companion controller" that talks OHCI or UHCI. The only
time EHCI gets involved in "low" or "full" speed transactions is
when they go through a "Transaction Translator"; those are built
into all high speed hubs. Otherwise, devices connected to EHCI
root hubs get switched to talk to the OHCI or UHCI "companion".
That "Transaction Translator" functionality involves new features
of the USB 2.0 protocol; no analogue for OHCI or UHCI.
- Dave
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