On Thu, 27 Jun 2013, William Gulland wrote: > Control transfers have both IN and OUT (or SETUP) packets, so when > clearing TT buffers for a control transfer it's necessary to send > two HUB_CLEAR_TT_BUFFER requests to the hub. What makes you think this is necessary? Have you found any hardware that requires this? Although the USB spec doesn't say much about Clear-TT-Buffer requests, the text in section 11.17.1 and Figure 11-47 seems to indicate that a second Clear-TT-Buffer shouldn't be needed. The spec says that TT buffers are matched based on the device address, endpoint number, and endpoint direction -- but the direction is used only for bulk endpoints, not for control endpoints. In particular, a control endpoint uses only one TT buffer for both the IN and OUT directions. So I don't think two Clear-TT-Buffers are needed. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
