iio: max31856: add option for setting mains filter rejection frequency

This sensor has an embedded notch filter for reducing interferences caused
by the power mains. This filter can be tuned to reject either 50Hz or 60Hz
(and harmonics).

Currently the said setting is left alone (the sensor defaults to 60Hz).
This patch introduces a IIO attribute that allows the user to set the said
filter to the desired frequency.

NOTE: this has been intentionally not tied to any DT property to allow
the configuration of this setting from userspace, e.g. with a GUI or by
reading a configuration file, or maybe reading a GPIO tied to a physical
switch or accessing some device that can autodetect the line frequency.

Cc: Hartmut Knaack <[email protected]>
Cc: Lars-Peter Clausen <[email protected]>
Cc: Peter Meerwald-Stadler <[email protected]>
Cc: Colin Ian King <[email protected]>
Cc: Patrick Havelange <[email protected]>
Cc: Matt Weber <[email protected]>
Cc: Matt Ranostay <[email protected]>
Cc: Chuhong Yuan <[email protected]>
Cc: Daniel Gomez <[email protected]>
Cc: [email protected]
Signed-off-by: Andrea Merello <[email protected]>
Reviewed-by: Matt Ranostay <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>

0 files changed, 0 insertions, 0 deletions