On Wed, 22 Sep 2004, David Brownell wrote: > >>This leaves some unanswered questions. On some buses (such as PCI or > >>USB), it's not possible to access a device whenever its state is higher > >>than 0. > > Not quite true. PCI config space access is allowed, which is how > things move from D1 to D2, or D2 to D3hot, etc. And I suppose it'd > make sense that CardBus, PCI Hotplug, and similar variants be able > to "enter" D3cold ... e.g. by powering off the slot then removing the > device. That's the same thing USB can do with suspended devices: > power off the hub port.
I should have said that it's not possible to access a device when its parent's state is higher than 0. So when the device and its parent are both lightly suspended, how do you increase the device's state? Oliver mentioned a good example: a disk drive (not necessarily USB, and not necessarily external to the computer) that uses some command set to control its power level. When direct access to the drive is no longer possible, how can you change the power level? On Wed, 22 Sep 2004, Oliver Neukum wrote: > If you want to suspend the whole system this is what you would likely > do anyway, as you potentially need to allocate a lot of ram or write > the system state to swap. So maybe you need to power-up one disk drive to access a swap partition. That doesn't mean all the other suspended devices should be woken just in order to put the system to sleep. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by: YOU BE THE JUDGE. Be one of 170 Project Admins to receive an Apple iPod Mini FREE for your judgement on who ports your project to Linux PPC the best. Sponsored by IBM. Deadline: Sept. 24. Go here: http://sf.net/ppc_contest.php _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
