Messages in this thread | | | Date | Sun, 8 Oct 2006 21:19:37 +0200 | From | Pavel Machek <> | Subject | Re: [linux-usb-devel] error to be returned while suspended |
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Hi!
> > > OK, let me state the basics. > > > > > > To get real power savings, we: > > > - blank the display > > > - spin down the hard drive > > > - put the CPU into an ACPI sleep state > > > > > > To do the latter well, we need to make sure there's no DMA. It is > > > important that less or little DMA will not help. We need no DMA. > > > So we need to handle the commonest scenarios fully. > > > > > > I dare say that the commonest scenario involving USB is a laptop with > > > an input device attached. Input devices are for practical purposes always > > > opened. A simple resume upon open and suspend upon close is useless. > > > > Okay, but you can simply do autosuspend with remote wakeup completely > > inside input driver. You do ot need it to be controlled from X... at > > most you need one variable ('autosuspend_inactivity_timeout') > > controlled from userland. > > > > That's what we already do for hdd spindown... you simply tell disk to > > aitospindown after X seconds of inactivity. > > The firmware in the drive supplies this function. It's hardly by choice > that it is made available. The power management functions without > timeout are also exported. For other power control features like > cpu frequency considerable effort has been made to export them to > user space. > > A simple timeout solution has drawbacks. > > - there's no guarantee the user wants wakeup (think laptop on > crowded table)
If you do not want wakeups (=> do not want any input from that device), then close that device.
> - you want to suspend immediately when you blank the screen (or switch to > a text console)
I kind-of understand "when you blank", but I do not think this mandatory. Why would you want to suspend when switching to text console? Am I no longer allowed to use gpm?
> - you want to consider all devices' activity. I am not pleased if my mouse > becomes less responsive just because I used only the keyboard for a > few minutes. Coordinating this inside the driver is hard as some input > devices might well be not usb (eg. bluetooth mouse, usb tablet)
Yep, that would be nice; but not at price of /sys/.../power/state like monstrosity that never ever worked properly. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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