Am Mittwoch, 21. Juli 2010, 22:43:48 schrieben Sie: > > Okay, good. Could we put the link into a low-power state instead of > > disabling it? Ideally, a state from which it won't return to full > > power until there's a disconnect or a reset? > > Yes, I think we can. Link PM is designed to be handled by the devices > on the bus, not software, but there is commands to force devices into > lower power link states. SetPortFeature(PORT_LINK_STATE) = U1 or U2. > Figure 7-13 shows that if there's a device removal or a reset, then the > link state machine transitions back to Rx.Detect from any other state. > > However, the SetPortFeature(PORT_LINK_STATE) for U1 or U2 will fail if > the link isn't in U0 to start with. So we'd have to force the link into > U0 first, and then force it into U2. I think we would also have to > disable the U1 and U2 timers too, otherwise the device could transition > into U1 from U0 before we could force it into U2. If I read section 7.2.4.2 of the USB 3.0 spec correctly, a device may refuse to put its link into U1 or U2. Regards Oliver -- 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
