Re: [PATCH 2/2] USB: ehci-tegra: fix inefficient copy of unaligned buffers

Johan Hovold
2015-04-07T19:59:37Z

On Tue, Apr 07, 2015 at 11:30:15AM -0400, Alan Stern wrote:
> On Tue, 7 Apr 2015, Johan Hovold wrote:
>
> > Make sure only to copy any actual data rather than the whole buffer,
> > when releasing the temporary buffer used for unaligned transfer buffers.
> >
> > Note that the corresponding fix of musb also fixes a lockup on
> > disconnect, where repeated failed transfers would starve the hub
> > workqueue from processing the disconnect, which would have prevented the
> > urbs from being resubmitted. In this case there is no data to forward,
> > but the full buffer length was being copied nonetheless.
>
> This is wrong for isochronous transfers, because the transfer data
> generally isn't contiguous in memory.
>
> It would be okay to do this for other transfer types, though.

Thanks for pointing that out. I'll re-spin the series tomorrow.

Johan