Messages in this thread | | | Date | Sat, 15 Oct 2011 08:47:32 +1100 | From | NeilBrown <> | Subject | Re: [: [RFC] wake up notifications and suspend blocking (aka more wakelock stuff)] |
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On Thu, 13 Oct 2011 11:16:23 -0400 (EDT) Alan Stern <stern@rowland.harvard.edu> wrote:
> On Thu, 13 Oct 2011, NeilBrown wrote: > > > Nope, but I'm keen for you to convince me. Identify a wakeup event that > > cannot be made visible to poll (or to user-space by some other > > mechanism) before the wakeup_source needs to be deactivated. Or if I've > > misunderstood what sort of notification is problematic, help me understand. > > Here's an example (just for kicks, not completely relevant to your > discussion): A USB keyboard key release. Unlike key presses, key > releases need not generate input events. If no processes are > monitoring the raw keyboard event queue then the release is not visible > to userspace at all, hence not visible before the wakeup_source needs > to be deactivated. > > Alan Stern
As you say, not completely relevant.
If a tree falls in a forest with no one to here, does it make a sound?
similarly if an event happens that no-one is looking for, is it visible? It doesn't really matter.
So at most this is a case of "is not made visible" rather than "cannot be made visible".
The key-release just needs to clear the "key is pressed" state so that auto-repeat stops and if it was a modifier, the modification is discarded. That is all trivially done in some kernel driver while the wakeup_source is active.
Thanks, NeilBrown [unhandled content-type:application/pgp-signature] | |