staging:iio:accel:sca3000 Fix clearing of flag + setting of size of scan.

Not clearing the stuff_to_read flag can lead to a false flag being set
on restarting the buffer if the data was not all read the previous time.

The size of the scan is needed to ensure the function
iio_buffer_read_first_n_outer actually tries to read the data.

This stuff has been broken for some time so not stable material.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>

drivers/staging/iio/accel/sca3000.c

@@ -1491,6 +1491,19 @@ int __sca3000_hw_ring_state_set(struct iio_dev *indio_dev, bool state)
  **/
 static int sca3000_hw_ring_preenable(struct iio_dev *indio_dev)
 {
+	/*
+	 * Set stuff to read to indicate no data present.
+	 * Need for cases where the interrupt had fired at the
+	 * end of a cycle, but the data was never read.
+	 */
+	indio_dev->buffer->stufftoread = 0;
+	/*
+	 * Needed to ensure the core will actually read data
+	 * from the device rather than assuming no channels
+	 * are enabled.
+	 */
+	indio_dev->buffer->bytes_per_datum = 6;
+
 	return __sca3000_hw_ring_state_set(indio_dev, 1);
 }