Re: [RFC PATCH 0/3] io: imu: st_lsm6dsx: wake on acc event

[Jonathan Cameron <jic23@jic23.retrosnub.co.uk>]

On Sun, 16 Jun 2019 14:24:31 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 14 Jun 2019 14:26:01 +0200
> Sean Nyekjaer <sean@geanix.com> wrote:
> 
> > Hi,
> > 
> > The first patch enables the wake event creation in the suspend function,
> > it hardcodes the accelerometer to low power mode and the gyro is powered down.
> > 
> > The second and third patch is where I have some questions.
> > Is it okay to create an sysfs entry that can enable and disable the wake
> > events from the accelerometer?  
> 
> On that I'm not sure - is there a standard way of configuring wake up events
> outside of IIO?
> 
> > 
> > The third patch is enabling us to set the threshold value.
> > Obviously this will need to be changed to represent a real value instead
> > of the raw register value.
> > Maybe I need to add a threshold avaliable sysfs entry?
> > Do I set it to a raw value calculated from the scale value or is some have
> > a better idea?  
> Yes, if a device is providing a _raw channel reading then threshold
> values should also be raw.
> 
> Available sysfs attribute makes sense if it helps a user, or userspace
> program to set the value.
> 
> > 
> > Finally is this the right approach to enable wake on accelerometer
> > events?
> > Please provide some idea's to how we could do it in the best and most
> > generic way.  
> 
> It's not something I've come across before, so hopefully someone else
> can provide guidance on this!
> 
> My only immediate thought is that perhaps this should be a device tree
> thing rather than userspace controlled?
doh. Should have read the patches first rather than just replying to the
cover letter ;) Ignore this bit!

> There also seems to be some existing infrastructure to control this
> in the power directory for a device.
> 
> Documentation/ABI/testing/sysfs-devices-power
> 
> Thanks,
> 
> Jonathan
> 
> > 
> > /Sean
> > 
> > Sean Nyekjaer (3):
> >   iio: imu: st_lsm6dsx: add wake on accelerometer threshold
> >   iio: imu: st_lsm6dsx: add wake on accelerometer enable hook in sysfs
> >   iio: imu: st_lsm6dsx: add wake on accelerometer threshold hook in
> >     sysfs
> > 
> >  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h      |   2 +
> >  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 135 +++++++++++++++++++
> >  2 files changed, 137 insertions(+)
> >   
>