Re: xHCI: Limiting host bInterval for super speed endpoints for Texas Instruments host controllers

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On Thu, Jun 30, 2011 at 01:48:17PM -0500, Dwight Schauer wrote:
> Thanks Alan and Sarah.
> 
> On Thu, Jun 30, 2011 at 1:22 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Thu, 30 Jun 2011, Sarah Sharp wrote:
> >> On Thu, Jun 30, 2011 at 09:19:02AM -0500, Schauer, Dwight wrote:
> >> > I'm putting the clamping of bInterval in xhci_endpoint_init, but am not sure if this is the correct location.
> >>
> >> It's probably the right place for it.  Another way to do it might be to
> >> have the USB core change the stored device descriptors before drivers
> >> have a chance to bind to the device.  Alan might have an opinion on
> >> this.
> 
> OK, I had not followed how ep_ctx->ep_info is being used higher up,
> this just seemed to be the place to put it. Do I need to do something
> specific with ep_ctx->ep_info in xhci_endpoint_init, or is that
> handled automatically to set the bInterval?

The xhci_ep_ctx structure is used to tell the xHCI host controller
information about the newly added endpoint, so it's really for lower
down, not higher up. :)  Your patch makes sure to clamp the
xhci_ep_ctx->ep_info value to 7, so the host controller will never see
an interval greater than 7 during a Configure Endpoint command.  The
xHCI driver ignores the URB's interval value right now, except for
printing a warning if the URB's value differs from the value passed to
the hardware.

The xhci_ep_ctx structure is specific to just the xHCI driver.  I don't
think we want to change the bInterval value in the USB core's stored
endpoint descriptor.  So your patch should be sufficient.

Sarah Sharp
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