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

From: Gerd Hoffmann
Subject: Re: [Qemu-devel] [PATCH 1/2] hw/usb-ohci: Honour endpoint maximum packet size
Date: Thu, 15 Sep 2011 11:13:20 +0200
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20110904 Red Hat/3.1.14-1.el6_1 Thunderbird/3.1.14

On 09/15/11 10:36, Peter Maydell wrote:
On 15 September 2011 08:33, Gerd Hoffmann<address@hidden>  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 "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 ...


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