struct iio_buffer_setup_ops — buffer setup related callbacks
struct iio_buffer_setup_ops {
  int (* preenable) (struct iio_dev *);
  int (* postenable) (struct iio_dev *);
  int (* predisable) (struct iio_dev *);
  int (* postdisable) (struct iio_dev *);
  bool (* validate_scan_mask) (struct iio_dev *indio_dev,const unsigned long *scan_mask);
};  [DRIVER] function to run prior to marking buffer enabled
[DRIVER] function to run after marking buffer enabled
[DRIVER] function to run prior to marking buffer disabled
[DRIVER] function to run after marking buffer disabled
[DRIVER] function callback to check whether a given scan mask is valid for the device.