iio:st_pressure: temperature triggered buffering

BugLink: https://bugs.launchpad.net/bugs/1676356

Enable support for triggered buffering of temperature samples.
Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
(cherry picked from commit b4701fd6)
Signed-off-by: Shrirang Bagul <shrirang.bagul@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/iio/pressure/st_pressure_core.c

@@ -105,8 +105,6 @@
 #define ST_PRESS_LSB_PER_CELSIUS		480UL
 #define ST_PRESS_MILLI_CELSIUS_OFFSET		42500UL
 
-#define ST_PRESS_NUMBER_DATA_CHANNELS		1
-
 /* FULLSCALE */
 #define ST_PRESS_FS_AVL_1100MB			1100
 #define ST_PRESS_FS_AVL_1260MB			1260
@@ -226,7 +224,7 @@ static const struct iio_chan_spec st_press_1_channels[] = {
 		.type = IIO_PRESSURE,
 		.channel2 = IIO_NO_MOD,
 		.address = ST_PRESS_1_OUT_XL_ADDR,
-		.scan_index = ST_SENSORS_SCAN_X,
+		.scan_index = 0,
 		.scan_type = {
 			.sign = 'u',
 			.realbits = 24,
@@ -241,7 +239,7 @@ static const struct iio_chan_spec st_press_1_channels[] = {
 		.type = IIO_TEMP,
 		.channel2 = IIO_NO_MOD,
 		.address = ST_TEMP_1_OUT_L_ADDR,
-		.scan_index = -1,
+		.scan_index = 1,
 		.scan_type = {
 			.sign = 'u',
 			.realbits = 16,
@@ -254,7 +252,7 @@ static const struct iio_chan_spec st_press_1_channels[] = {
 			BIT(IIO_CHAN_INFO_OFFSET),
 		.modified = 0,
 	},
-	IIO_CHAN_SOFT_TIMESTAMP(1)
+	IIO_CHAN_SOFT_TIMESTAMP(2)
 };
 
 static const struct iio_chan_spec st_press_lps001wp_channels[] = {
@@ -262,7 +260,7 @@ static const struct iio_chan_spec st_press_lps001wp_channels[] = {
 		.type = IIO_PRESSURE,
 		.channel2 = IIO_NO_MOD,
 		.address = ST_PRESS_LPS001WP_OUT_L_ADDR,
-		.scan_index = ST_SENSORS_SCAN_X,
+		.scan_index = 0,
 		.scan_type = {
 			.sign = 'u',
 			.realbits = 16,
@@ -278,7 +276,7 @@ static const struct iio_chan_spec st_press_lps001wp_channels[] = {
 		.type = IIO_TEMP,
 		.channel2 = IIO_NO_MOD,
 		.address = ST_TEMP_LPS001WP_OUT_L_ADDR,
-		.scan_index = -1,
+		.scan_index = 1,
 		.scan_type = {
 			.sign = 'u',
 			.realbits = 16,
@@ -290,7 +288,7 @@ static const struct iio_chan_spec st_press_lps001wp_channels[] = {
 			BIT(IIO_CHAN_INFO_SCALE),
 		.modified = 0,
 	},
-	IIO_CHAN_SOFT_TIMESTAMP(1)
+	IIO_CHAN_SOFT_TIMESTAMP(2)
 };
 
 static const struct iio_chan_spec st_press_lps22hb_channels[] = {
@@ -660,7 +658,13 @@ int st_press_common_probe(struct iio_dev *indio_dev)
 	if (err < 0)
 		goto st_press_power_off;
 
-	press_data->num_data_channels = ST_PRESS_NUMBER_DATA_CHANNELS;
+	/*
+	 * Skip timestamping channel while declaring available channels to
+	 * common st_sensor layer. Look at st_sensors_get_buffer_element() to
+	 * see how timestamps are explicitly pushed as last samples block
+	 * element.
+	 */
+	press_data->num_data_channels = press_data->sensor_settings->num_ch - 1;
 	press_data->multiread_bit = press_data->sensor_settings->multi_read_bit;
 	indio_dev->channels = press_data->sensor_settings->ch;
 	indio_dev->num_channels = press_data->sensor_settings->num_ch;