For adding newer sensor some basic rework of the code is necessary.

This commit reworks the code and allows the sampling start/end code and
the position of value readout register to be altered. Later the start/end
functions will be used to configure the ths and start/stop the
sampling.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Philipp Rossak <redacted>
---
 drivers/iio/adc/sun4i-gpadc-iio.c | 44 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 39 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/sun4i-gpadc-iio.c b/drivers/iio/adc/sun4i-gpadc-iio.c
index 03804ff9c006..db57d9fffe48 100644
--- a/drivers/iio/adc/sun4i-gpadc-iio.c
+++ b/drivers/iio/adc/sun4i-gpadc-iio.c

@@ -49,6 +49,15 @@ static unsigned int sun6i_gpadc_chan_select(unsigned int chan)
 	return SUN6I_GPADC_CTRL1_ADC_CHAN_SELECT(chan);
 }
 
+struct sun4i_gpadc_iio;
+
+/*
+ * Prototypes for these functions, which enable these functions to be
+ * referenced in gpadc_data structures.
+ */

+static int sun4i_gpadc_sample_start(struct sun4i_gpadc_iio *info);
+static int sun4i_gpadc_sample_end(struct sun4i_gpadc_iio *info);
+
 struct gpadc_data {
 	int		temp_offset;
 	int		temp_scale;

@@ -56,6 +65,9 @@ struct gpadc_data {
 	unsigned int	tp_adc_select;
 	unsigned int	(*adc_chan_select)(unsigned int chan);
 	unsigned int	adc_chan_mask;
+	unsigned int	temp_data;