On Mon, Jun 24, 2013 at 10:56:30PM +0800, Ming Lei wrote: > On Mon, Jun 24, 2013 at 10:33 PM, Denis V. Lunev <d...@openvz.org> wrote: > > From: Konstantin Filatov <kfila...@parallels.com> > > > > This patch shortens TD's packet not only for the last TD in sg list, > > but also for the last TD in sg element. > > > > Signed-off-by: Konstantin Filatov <kfila...@parallels.com> > > Signed-off-by: Denis V. Lunev <d...@openvz.org> > > Considered that: > > - the change violates USB spec(1.1/2.0/3.0)
I can't see how this would violate USB spec. USB specifications have no knowledge of scatter-gather. It really doesn't matter how the data gets into the HW's FIFO, as long as it *does* get there. IOW an SG table like below: sg[0].length = 512 sg[1].length = 512 sg[2].length = 20 is no different than: sg[0].length = 502 sg[1].length = 512 sg[2].length = 30 from the USB perspective, all is sees is 1044 bytes being shifted through the data lines. > - the problem should be avoided in usbcore since it isn't a uhci > specific problem to this I agree. > - this patch only hides problem, doesn't help to fix real problem. what is the problem then ? Are you saying that it's wrong to have an sg which is not aligned to wMaxPacketSize somewhere in the middle of an sg-table ? How so ? What does that have to do with USB at all ? -- balbi
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