Re: dell-laptop and separate AC timeouts on some Dell systems

["Pali Rohár" <pali.rohar@gmail.com>]

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On Saturday 08 April 2017 04:09:11 Mario.Limonciello@dell.com wrote:
> > > The difference is that intensity it's obvious that it changes
> > > from 50 to 100 percent.  With different timeouts, shouldn't this
> > > be more complex?
> > 
> > Currently for keyboard backlight settings is used procedure:
> > get current status --> update --> set new status.
> > 
> > So we just need to have two timeouts in struct kbd_state and
> > get/set functions needs to handle it. I do not thing this change
> > would be complex, it should be straightforward.
> 
> Yeah I figured this part was straightforward, it was the second part
> that was more complex :)
> 
> > > Would you just keep two different nodes as accessible to
> > > userspace?
> > 
> > And this is another question... For a first step we should just fix
> > timeout sysfs node to work. And probably the best fix would be
> > that this node will manage timeout which belongs to current AC or
> > battery state.
> 
> So the easiest way to implement this would be to save/restore the
> values from the cbArg3 that are not currently saved without to
> regard to whether the platform supports a dedicated AC timeout.
> 
> If it doesn't support a dedicated AC timeout this will be a no-op,
> but if it does it will fix this problem.

We can detect at module load time if notebook is new or old and based on 
this fact we can fill or not cbArg3.

> > Like for dell_get_intensity(). When notebook is running on battery
> > we will export timeout configured for battery and when on AC we
> > will export timeout configured for AC. Changing timeout via sysfs
> > just affect only one (current) configuration (ac or battery).
> 
> So basically the value in sysfs would change when you added/removed
> the AC adapter?  That might be a little bit confusing to a user in
> my opinion.
> 
> > IIRC we do not provide a sysfs node for changing AC display panel
> > brightness level when notebook is running on battery and vice
> > versa. So do we need it for keyboard backlight timeout at all?
> 
> How is that handled then?  The node dynamically changes values based
> on if a power adapter is plugged in?

Node has read and store functions. Those function check if AC is 
connected and based on this state variant for AC or battery is called.

There is no need to active monitoring plug of power adapter.

-- 
Pali Rohár
pali.rohar@gmail.com

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