Re: USB 3.0 gadget stack

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On Sat, Jan 31, 2009 at 12:08:49PM +0530, Viral Mehta wrote:
>
>> Of course these changes discussed don't even cover the new link power
>> management and function suspend for USB 3.0 devices.  Those will both be
>> a requirement for USB 3.0 device compliance, but we can discuss those
>> after we have an idea of the changes necessary for basic USB 3.0
>> gadget-side support.
>>
>> Can anyone think of any other changes for USB 3.0 gadget side support?
>>   
> I still do not understand how exactly core and gadget side driver or  
> controller or peripheral controller will address
> backward/forward compatibility issues.
>
> Like USB3.0 device can be attached to USB2.0 bus and USB2.0 devices can  
> be attached to USB3.0 bus.

A USB 3.0 device attached to a USB 2.0 port will show up as a USB 2.0
device.  The USB 3.0 device will not see the USB 3.0 terminations and
will just enumerate as a USB 2.0 device with USB 2.0 device descriptors.
No support is necessary for that case, because the USB core knows how to
deal with USB 2.0 devices.

For the case of a USB 2.0 device plugged into a USB 3.0 port (under
xHCI, presumably), there will need to be some changes to support the
xHCI driver.  Those changes are part of my xHCI host controller
patchset.

Sarah
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