On Tue, 24 Jan 2006, David Brownell wrote: > Last I looked at UHCI docs, there wasn't any other way to tell > whether system wakeup was supported ... short of looking at the > ACPI tables that are currently in /proc/acpi/wakeup and not yet > integrated into the driver model. (Assuming ACPI is in use...)
Some Intel motherboards have documentation indicating that system wakeup can be enabled by setting some bits in the UHCI controller's PCI config space. Presumably that information is also present in the ACPI tables. Beyond that, I haven't seen any indication either. The only USB card I've got with PCI PM support provides that support just for the EHCI controller, not for the companion UHCI controllers. > But the root hub itself would always be able to handle (runtime) > wakeup events. Ah, "would always be able", yes, but _should_ it handle these events when the wakeup_enabled flag is off? > > But I've forgotten exactly what the root hub's wakeup_enabled flag is > > supposed to mean (and I can't find where it's documented, if anywhere). > > It's not especially different from any other device. For USB > hubs, the wakeup events certainly include "remote wakeup" but > (in general) also device connect/disconnect. The USB spec treats these two classes of events slightly differently. With external hubs, there's no way to disable the response to a remote wakeup signal received from downstream. The hub, if it isn't suspended itself, will _always_ clear the port's suspend feature and set the suspend-changed bit. If the hub is suspended it will _always_ relay the remote wakeup signal upstream. But when an external hub is suspended, its response to device connect/disconnect is dictated by the wakeup-enable feature. If that feature isn't set, the hub will not generate a remote wakeup signal when those events occur. The spec doesn't say exactly how a root hub is supposed to behave in these circumstances. Presumably we want to imitate an external hub as closely as is feasible. That would mean (assuming the root hub is suspended and the controller isn't, which implies we're talking about runtime PM) that the root hub always responds to remote wakeup signals, but it responds to connect/disconnect only when wakeup-enabled is on. Unfortunately, for UHCI at least, there doesn't seem to be any simple way to treat the two types of events differently. Either the root hub always responds to all events, or else it doesn't respond to any events when wakeup-enabled is off. Which way do you think it should behave? Alan Stern ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=103432&bid=230486&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
