Messages in this thread |  | | Subject | Re: A desktop environment[1] kernel wishlist | From | Bastien Nocera <> | Date | Tue, 28 Oct 2014 13:36:45 +0100 |
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On Mon, 2014-10-27 at 16:59 -0400, Zygo Blaxell wrote: > On Mon, Oct 27, 2014 at 03:28:04PM +0100, Bastien Nocera wrote: > > On Wed, 2014-10-22 at 13:04 -0400, Zygo Blaxell wrote: > > > On Tue, Oct 21, 2014 at 08:09:38PM +0200, Bastien Nocera wrote: > > > > On Tue, 2014-10-21 at 11:00 -0700, John Stultz wrote: > > > > > On Tue, Oct 21, 2014 at 10:14 AM, Bastien Nocera <hadess@hadess.net> wrote: > > > > > >> As for: 'Export of "wake reason" when the system wakes up (rtc alarm, > > > > > >> lid open, etc.) and wakealarm (/sys/class/rtc/foo/wakealarm) > > > > > >> documentation' > > > > > >> > > > > > >> Can you expand more on the rational for the need here? Is this for UI > > > > > >> for power debugging, or something else? > > > > > > > > > > > > No, it would be used for automating backups, or implementing > > > > > > suspend->hibernation transitions. For example, right before the machine > > > > > > suspends, I would schedule it to wake up in a hour. If I get woken up by > > > > > > the rtc alarm (and not by the user through a lid open), I might: > > > > > > - check that I'm plugged into the AC, it's night, and in the vicinity of > > > > > > the server that handles my backups and so backup the system. > > > > > > - check whether the battery is low, and hibernate the machine (if it > > > > > > supports it, obviously). > > > > > > > > > > > > We cannot do that if we can't make out whether the wake-up came from a > > > > > > user action, or the alarm we set. > > > > > > > > > > I suspect wakeup type reporting is maybe not the best way to go about > > > > > this, since there may be a number of causes for wakeups and they can > > > > > arrive closely together in different orders, which can result in > > > > > races. > > > > > > > > > > For instance, if the machine suspends, and sets an alarm to be woken > > > > > up at midnight to do a backup, if the user resumes their laptop at > > > > > 11:59:59, should the backup still proceed at midnight? > > > > > > > > No. And I would expect that we would get a wake up type of "power > > > > button" or "lid open" in this case. > > > > > > I have been using something like this for the last 7 years or so. > > > The relevant inputs are: > > > > > > 1. is the user present (is there recent input on HID devices, > > > keyboard/mouse, but ignore devices like light sensors, 3D > > > accelerometers, and ACPI virtual keys)? > > > > If the user woke the machine up through the power button, you wouldn't > > see that from user-space. You could detect that the lid was opened, > > because you have state. > > > > > 2. which network connection(s) are available to reach the > > > backup server? > > > > > > 3. how much power is available (if on battery, how much run > > > time left?) > > > > > > 4. what is the policy (do backups happen at a specific time > > > of day, or whenever they can?) > > > > > > 5. was a backup completed successfully in the last N hours? > > > > > > Note the absence of any information about the cause of recent > > > suspend/resume activity, or any input from suspend/resume at all. > > > > How do I tell my environment not to wake the screen up when the machine > > was woken up by an alarm I scheduled to launch a backup? > > Lid closed? Screen off (nobody can see it, it wastes power on battery, > and lengthens charge time on AC). > > Lid open and user input? Screen on. > > Lid open and user disabled time-based screen power saving? Screen on. > > These are not symmetrical. To wake up the screen, the screen needs to > be visible, and the policy conditions to wake up the screen need to be > met. Spontaneously firing up a backlight at full power in a dark room > in the middle of the night may not be appreciated by the system owner.
How do I detect that the screen is visible on a tablet? I could turn on the webcam to see if a face is detected ;)
Maybe the wake-up reason isn't good enough on its own, but how do I know which one the possible wake-up reasons was the last one to trigger?
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