Re: [PATCH] gpio_keys, twl4030-pwrbutton: stay awake for 1sec on resume

[Pavel Machek <pavel@ucw.cz>]

Hi!

> >> This gives the userspace (Replicant) a chance to fully handle the
> >> pm_wakeup_event, before autosleep suspends the system alltogether
> >> again.
> >> 
> >> This fixes suspend/resume on the OpenPhoenux GTA04, in combination with
> >> the Replicant 4.2.2 userspace, which needs to execute this to stay
> >> awake: 'echo on > /sys/power/state'
> >> 
> >> Signed-off-by: Lukas Märdian <lukas@goldelico.com>
> >> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
> > 
> > I'm sorry, but we should not be doing this.
> > 
> > You basically put a delay in driver to work around userspace bug.
> 
> Do you think it is a user-space bug if the kernel goes to sleep again
> before giving user space any chance to react to an event?

Well, who says 1000msec is enough? Some userspace may need
more. ... for example on PC when you keyboard-handling deamon is
swapped out.

> And the msec parameter is described as:
> 
> @msec: Anticipated event processing time (in milliseconds).
> 
> Isn't calling pm_wakeup_event() with a non-zero msec the standard
> method to handle this situation? And it is used in other drivers. E.g. in
> _mmc_detect_change() or hub_suspend().

 * Notify the PM core of a wakeup event whose source is @ws that will
   take                    
 * approximately @msec milliseconds to be processed by the kernel.  If
   @ws is                 
 * not active, activate it.  If @msec is nonzero, set up the @ws'
   timer to                    
 * execute pm_wakeup_timer_fn() in future.                                                    

Will take @msec milliseconds to be processed by the _kernel_. Yes, USB
probing takes a lot of time in kernel. But you are using this
parameter to wait for userspace...

> > There must be better
> > solution....
>  
> I am not sure how it could look like.

Rafael, do you have any idea how this is supposed to work?

Original patch is at https://lkml.org/lkml/2014/4/10/156 .
									Pavel

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