On Mon, 20 Mar 2006, Steve Calfee wrote:
> Hi Alan,
>
> I think the confusion is endpoints vs connectors. There is nothing illegal
> about having multiple usb bus connections on one device. They could even be
> plugged into the same bus, but they would be enumerated seperately and given
> different USB addresses.
Technically you're correct. Legally I'm not sure. My understanding was
that the USB spec prohibited attaching a USB device to more than one bus.
However I can't find any place in the spec where it says that. Instead,
section 6.4.4 (Prohibited Cable Assemblies) says:
Cable assembly that violates USB topology rules
A cable assembly with both ends terminated in either Series "A"
plugs or Series "B" receptacles. This allows two downstream ports
to be directly connected.
Note: This prohibition does not prevent using a USB device to
provide a bridge between two USB buses.
So maybe my understanding was wrong.
> I don't know why a PCI device could not have
> several cards in one PC. You may be right about the Gadget API.
Again, there's no technical reason why you can't have several device-type
PCI cards in one PC. The crucial aspect that's missing in the Gadget API
is a way to specify which controller a gadget driver should be bound to.
If there was more than one controller in your computer, when the gadget
driver registered it might end up getting bound to all of them or only to
one chosen at random.
Not to mention the fact that all the existing USB device controller
drivers and gadget drivers assume that they will control a single
interface. The drivers could be changed easily enough to support multiple
interfaces, however. The weak point would still lie in determining which
gadget driver should be bound to which interface.
Alan Stern
-------------------------------------------------------
This SF.Net email is sponsored by xPML, a groundbreaking scripting language
that extends applications into web and mobile media. Attend the live webcast
and join the prime developer group breaking into this new coding territory!
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
_______________________________________________
[email protected]
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
