Re: [Qemu-devel] [PATCH 1/2] hw/usb-ohci: Honour endpoint maximum packet size

[Gerd Hoffmann <kraxel@redhat.com>]

On 09/15/11 10:36, Peter Maydell wrote:
> On 15 September 2011 08:33, Gerd Hoffmann<kraxel@redhat.com>  wrote:
>> On 09/14/11 19:48, Peter Maydell wrote:
>>>
>>> Honour the maximum packet size for endpoints; this applies when
>>> sending non-isochronous data and means we transfer only as
>>> much as the endpoint allows, leaving the transfer descriptor
>>> on the list for another go next time around. This allows
>>> usb-net to work when connected to an OHCI controller model.
>>
>> Hmm, I'd tend to fix it the other way around:  Fix usb-net to deal with
>> transfers larger than the endpoint packet size.  What do you think?
>
> Honouring maximum packet size is mandated by the OHCI spec:
> see section 4.3.1.3.2 "Packet Size" in OHCI specification 1.0a.
> Our failure to do it is just a bug in our controller model.

No.  What I think is that USBPacket shouldn't be required to be an 
actual USB packet, but a transfer, i.e. do the splitting of larger 
transfers into smaller packets in the usb driver emulation (if needed), 
not the host adapter emulation.

Maybe it is a good idea to rename USBPacket to USBTransfer to make that 
clear.

 > If you want to make our usb-net implementation permit and
 > advertise a larger max-packet-size (and test it for
 > interoperability with a pile of OSes :-)) that's a different
 > thing.

Also add usb 2.0 support while being at it.
But that is another story ...

cheers,
   Gerd