iio: adc: ad7380: prepare driver for single-ended parts support

ad738x family contains single-ended parts that have a 2:1 mux in front
of ADC, so the number of IIO channels is different from the number of
simultaneous channels that can be sampled.

To prepare the support for single-ended parts, introduce a new
num_simultaneous_channels variable. For currently supported parts,
num_simultaneous_channels is equal to num_channels minus 1 (the
timestamps channel)

Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240731-ad7380-add-single-ended-chips-v2-4-cd63bf05744c@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: justeph

drivers/iio/adc/ad7380.c

@@ -80,6 +80,7 @@ struct ad7380_chip_info {
 	const char *name;
 	const struct iio_chan_spec *channels;
 	unsigned int num_channels;
+	unsigned int num_simult_channels;
 	const char * const *vcm_supplies;
 	unsigned int num_vcm_supplies;
 	const unsigned long *available_scan_masks;
@@ -208,6 +209,7 @@ static const struct ad7380_chip_info ad7380_chip_info = {
 	.name = "ad7380",
 	.channels = ad7380_channels,
 	.num_channels = ARRAY_SIZE(ad7380_channels),
+	.num_simult_channels = 2,
 	.available_scan_masks = ad7380_2_channel_scan_masks,
 	.timing_specs = &ad7380_timing,
 };
@@ -216,6 +218,7 @@ static const struct ad7380_chip_info ad7381_chip_info = {
 	.name = "ad7381",
 	.channels = ad7381_channels,
 	.num_channels = ARRAY_SIZE(ad7381_channels),
+	.num_simult_channels = 2,
 	.available_scan_masks = ad7380_2_channel_scan_masks,
 	.timing_specs = &ad7380_timing,
 };
@@ -224,6 +227,7 @@ static const struct ad7380_chip_info ad7383_chip_info = {
 	.name = "ad7383",
 	.channels = ad7383_channels,
 	.num_channels = ARRAY_SIZE(ad7383_channels),
+	.num_simult_channels = 2,
 	.vcm_supplies = ad7380_2_channel_vcm_supplies,
 	.num_vcm_supplies = ARRAY_SIZE(ad7380_2_channel_vcm_supplies),
 	.available_scan_masks = ad7380_2_channel_scan_masks,
@@ -234,6 +238,7 @@ static const struct ad7380_chip_info ad7384_chip_info = {
 	.name = "ad7384",
 	.channels = ad7384_channels,
 	.num_channels = ARRAY_SIZE(ad7384_channels),
+	.num_simult_channels = 2,
 	.vcm_supplies = ad7380_2_channel_vcm_supplies,
 	.num_vcm_supplies = ARRAY_SIZE(ad7380_2_channel_vcm_supplies),
 	.available_scan_masks = ad7380_2_channel_scan_masks,
@@ -244,6 +249,7 @@ static const struct ad7380_chip_info ad7380_4_chip_info = {
 	.name = "ad7380-4",
 	.channels = ad7380_4_channels,
 	.num_channels = ARRAY_SIZE(ad7380_4_channels),
+	.num_simult_channels = 4,
 	.available_scan_masks = ad7380_4_channel_scan_masks,
 	.timing_specs = &ad7380_4_timing,
 };
@@ -252,6 +258,7 @@ static const struct ad7380_chip_info ad7381_4_chip_info = {
 	.name = "ad7381-4",
 	.channels = ad7381_4_channels,
 	.num_channels = ARRAY_SIZE(ad7381_4_channels),
+	.num_simult_channels = 4,
 	.available_scan_masks = ad7380_4_channel_scan_masks,
 	.timing_specs = &ad7380_4_timing,
 };
@@ -260,6 +267,7 @@ static const struct ad7380_chip_info ad7383_4_chip_info = {
 	.name = "ad7383-4",
 	.channels = ad7383_4_channels,
 	.num_channels = ARRAY_SIZE(ad7383_4_channels),
+	.num_simult_channels = 4,
 	.vcm_supplies = ad7380_4_channel_vcm_supplies,
 	.num_vcm_supplies = ARRAY_SIZE(ad7380_4_channel_vcm_supplies),
 	.available_scan_masks = ad7380_4_channel_scan_masks,
@@ -270,6 +278,7 @@ static const struct ad7380_chip_info ad7384_4_chip_info = {
 	.name = "ad7384-4",
 	.channels = ad7384_4_channels,
 	.num_channels = ARRAY_SIZE(ad7384_4_channels),
+	.num_simult_channels = 4,
 	.vcm_supplies = ad7380_4_channel_vcm_supplies,
 	.num_vcm_supplies = ARRAY_SIZE(ad7380_4_channel_vcm_supplies),
 	.available_scan_masks = ad7380_4_channel_scan_masks,
@@ -407,7 +416,7 @@ static void ad7380_update_xfers(struct ad7380_state *st,
 	 */
 	st->xfer[1].bits_per_word = scan_type->realbits;
 	st->xfer[1].len = BITS_TO_BYTES(scan_type->storagebits) *
-			  (st->chip_info->num_channels - 1);
+			  st->chip_info->num_simult_channels;
 }
 
 static int ad7380_triggered_buffer_preenable(struct iio_dev *indio_dev)