On Tue, 28 Sep 2004, David Brownell wrote: > > But it's unavoidable that drivers will encounter devices that have lost > > power when resuming from the "idle" state -- and with no intervening power > > state transition -- if power isn't available (not even suspend power) > > while the system is off. > > That's why I said "accompanied by a power state transition". > Like turning the system off, or otherwise reducing power input; > and then issuing resume() calls. > > But if there was no power state transition, hence no resume(), > then a device losing power means a major hardware problem.
This is getting a little metaphysical... What I meant was that when resuming from an idle state, a driver has to expect that the device may have lost power even if it has no recollection of going through a power-off state transition. The transition may very well have occurred, as you say, but the driver will have no memory of it. So the driver can't assume that the device will still be in the same idle state as before. > > What about Oliver's objection that support for wakeup depends on the > > power level? Like he said, it's easier just to try turning on wakeup and > > see if you get a "not-supported" error. > > That's why I specified one bit controlling whether or not > the device should try to enable wakeup when it changes > into a suspend state. That copes with PCI restrictions, > but doesn't try to export them anywhere else (like to USB). Well, you actually specified "two bits in the driver model, one saying if the hardware supports wakeup and the other defining the policy." Just the second bit should be sufficient, considering that the meaning of the first bit is not well defined (it depends on the particular suspend state). Alan Stern ------------------------------------------------------- This SF.net email is sponsored by: IT Product Guide on ITManagersJournal Use IT products in your business? Tell us what you think of them. Give us Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more http://productguide.itmanagersjournal.com/guidepromo.tmpl _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
