Re: A desktop environment[1] kernel wishlist

Chirantan Ekbote
2015-05-05T20:58:19Z

On Tue, May 5, 2015 at 12:35 PM, Alan Stern <stern@rowland.harvard.edu> wrote:
> On Tue, 5 May 2015, Chirantan Ekbote wrote:
>
>> This is our plan for the next version (see my email earlier in this
>> thread). Keeping a hybrid power state with hacks in the drivers isn't
>> really maintainable, scalable, or upstream-able and has caused us some
>> headaches already. Unfortunately we were working with the 3.14 kernel
>> at the time, which didn't have the framework necessary to do anything
>> else. The new version of lucid sleep will have the power manager
>> runtime suspend power-hungry devices before a suspend so that they
>> remain powered off at resume time. The power manager can then decide
>> to resume those devices based on whether the wakeup event was
>> user-triggered.
>>
>> Being able to determine the wakeup type from userspace is the only
>> functionality we need from the kernel that doesn't already exist in
>> mainline.
>
> Maybe you can simplify the problem. You don't really need to know the
> wakeup type, or to determine which device was responsible for the
> wakeup. All you really need to know is whether the wakeup was
> user-triggered. That may be much easier to discover.
>

You are, of course, correct. Ultimately the only requirement we have
is that there exists a way for userspace to determine if the system
woke up because of a user-triggered event. The actual mechanism by
which this determination is made isn't something I feel strongly
about. The reason I had been focusing on exposing the actual wakeup
event to userspace is because classifying wakeup events as
user-triggered or not feels to me like a policy decision that should
be left to userspace. If the kernel maintainers are ok with doing
this work in the kernel instead and only exposing a binary yes/no bit
to userspace for user-triggered wakeups, that's perfectly fine because
it still meets our requirements.

> Alan Stern
>