Hi, On Mon, Jun 24, 2013 at 05:12:50PM +0200, Sebastian Andrzej Siewior wrote: > On 06/24/2013 05:04 PM, Felipe Balbi wrote: > >> - 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. > > It is a little. The first USB packet has 512 vs 502 bytes on the wire. you wouldn't notice the difference. The DMA engine is the one which would read the sgtable to figure where the data is scattered, at the end of the day, SW only knows of a single 1044bytes URB and controller is required to generate proper USB packets out of that. > But this is almost kidergarder. We have only mass storage using this > which does not do this. You can't even merge sgs at that level so that > you run in such a problem. So this is simply a tool used wrong. > I agree with the patch Alan acked. right, $subject is just a new version with improved subject line :-) -- balbi
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