[v4,4/5] iio: light: ROHM BU27008 color sensor

diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index 6fa31fcd71a1..7888fc439b2f 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -289,6 +289,20 @@  config JSA1212
 	  To compile this driver as a module, choose M here:
 	  the module will be called jsa1212.
 
+config ROHM_BU27008
+	tristate "ROHM BU27008 color (RGB+C/IR) sensor"
+	depends on I2C
+	select REGMAP_I2C
+	select IIO_GTS_HELPER
+	help
+	  Enable support for the ROHM BU27008 color sensor.
+	  The ROHM BU27008 is a sensor with 5 photodiodes (red, green,
+	  blue, clear and IR) with four configurable channels. Red and
+	  green being always available and two out of the rest three
+	  (blue, clear, IR) can be selected to be simultaneously measured.
+	  Typical application is adjusting LCD backlight of TVs,
+	  mobile phones and tablet PCs.
+
 config ROHM_BU27034
 	tristate "ROHM BU27034 ambient light sensor"
 	depends on I2C
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index 985f6feaccd4..82dec50a7e19 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -38,6 +38,7 @@  obj-$(CONFIG_MAX44009)		+= max44009.o
 obj-$(CONFIG_NOA1305)		+= noa1305.o
 obj-$(CONFIG_OPT3001)		+= opt3001.o
 obj-$(CONFIG_PA12203001)	+= pa12203001.o
+obj-$(CONFIG_ROHM_BU27008)	+= rohm-bu27008.o
 obj-$(CONFIG_ROHM_BU27034)	+= rohm-bu27034.o
 obj-$(CONFIG_RPR0521)		+= rpr0521.o
 obj-$(CONFIG_SI1133)		+= si1133.o
diff --git a/drivers/iio/light/rohm-bu27008.c b/drivers/iio/light/rohm-bu27008.c
new file mode 100644
index 000000000000..c04d845062ba
--- /dev/null
+++ b/drivers/iio/light/rohm-bu27008.c
@@ -0,0 +1,993 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * BU27008 ROHM Colour Sensor
+ *
+ * Copyright (c) 2023, ROHM Semiconductor.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/iio-gts-helper.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+#define BU27008_REG_SYSTEM_CONTROL	0x40
+#define BU27008_MASK_SW_RESET		BIT(7)
+#define BU27008_MASK_PART_ID		GENMASK(5, 0)
+#define BU27008_ID			0x1a
+#define BU27008_REG_MODE_CONTROL1	0x41
+#define BU27008_MASK_MEAS_MODE		GENMASK(2, 0)
+#define BU27008_MASK_CHAN_SEL		GENMASK(3, 2)
+
+#define BU27008_REG_MODE_CONTROL2	0x42
+#define BU27008_MASK_RGBC_GAIN		GENMASK(7, 3)
+#define BU27008_MASK_IR_GAIN_LO		GENMASK(2, 0)
+#define BU27008_SHIFT_IR_GAIN		3
+
+#define BU27008_REG_MODE_CONTROL3	0x43
+#define BU27008_MASK_VALID		BIT(7)
+#define BU27008_MASK_INT_EN		BIT(1)
+#define BU27008_INT_EN			BU27008_MASK_INT_EN
+#define BU27008_INT_DIS			0
+#define BU27008_MASK_MEAS_EN		BIT(0)
+#define BU27008_MEAS_EN			BIT(0)
+#define BU27008_MEAS_DIS		0
+
+#define BU27008_REG_DATA0_LO		0x50
+#define BU27008_REG_DATA1_LO		0x52
+#define BU27008_REG_DATA2_LO		0x54
+#define BU27008_REG_DATA3_LO		0x56
+#define BU27008_REG_DATA3_HI		0x57
+#define BU27008_REG_MANUFACTURER_ID	0x92
+#define BU27008_REG_MAX BU27008_REG_MANUFACTURER_ID
+
+/**
+ * enum bu27008_chan_type - BU27008 channel types
+ * @BU27008_RED:	Red channel. Always via data0.
+ * @BU27008_GREEN:	Green channel. Always via data1.
+ * @BU27008_BLUE:	Blue channel. Via data2 (when used).
+ * @BU27008_CLEAR:	Clear channel. Via data2 or data3 (when used).
+ * @BU27008_IR:		IR channel. Via data3 (when used).
+ * @BU27008_NUM_CHANS:	Number of channel types.
+ */
+enum bu27008_chan_type {
+	BU27008_RED,
+	BU27008_GREEN,
+	BU27008_BLUE,
+	BU27008_CLEAR,
+	BU27008_IR,
+	BU27008_NUM_CHANS
+};
+
+/**
+ * enum bu27008_chan - BU27008 physical data channel
+ * @BU27008_DATA0:		Always red.
+ * @BU27008_DATA0:		Always green.
+ * @BU27008_DATA0:		Blue or clear.
+ * @BU27008_DATA0:		IR or clear.
+ * @BU27008_NUM_HW_CHANS:	Number of physical channels
+ */
+enum bu27008_chan {
+	BU27008_DATA0,
+	BU27008_DATA1,
+	BU27008_DATA2,
+	BU27008_DATA3,
+	BU27008_NUM_HW_CHANS
+};
+
+/* We can always measure red and green at same time */
+#define ALWAYS_SCANNABLE (BIT(BU27008_RED) | BIT(BU27008_GREEN))
+
+/* We use these data channel configs. Ensure scan_masks below follow them too */
+#define BU27008_BLUE2_CLEAR3		0x0 /* buffer is R, G, B, C */
+#define BU27008_CLEAR2_IR3		0x1 /* buffer is R, G, C, IR */
+#define BU27008_BLUE2_IR3		0x2 /* buffer is R, G, B, IR */
+
+static const unsigned long bu27008_scan_masks[] = {
+	/* buffer is R, G, B, C */
+	ALWAYS_SCANNABLE | BIT(BU27008_BLUE) | BIT(BU27008_CLEAR),
+	/* buffer is R, G, C, IR */
+	ALWAYS_SCANNABLE | BIT(BU27008_CLEAR) | BIT(BU27008_IR),
+	/* buffer is R, G, B, IR */
+	ALWAYS_SCANNABLE | BIT(BU27008_BLUE) | BIT(BU27008_IR),
+	0
+};
+
+/*
+ * Available scales with gain 1x - 1024x, timings 55, 100, 200, 400 mS
+ * Time impacts to gain: 1x, 2x, 4x, 8x.
+ *
+ * => Max total gain is HWGAIN * gain by integration time (8 * 1024) = 8192
+ *
+ * Max amplification is (HWGAIN * MAX integration-time multiplier) 1024 * 8
+ * = 8192. With NANO scale we get rid of accuracy loss when we start with the
+ * scale 16.0 for HWGAIN1, INT-TIME 55 mS. This way the nano scale for MAX
+ * total gain 8192 will be 1953125
+ */
+#define BU27008_SCALE_1X 16
+
+/* See the data sheet for the "Gain Setting" table */
+#define BU27008_GSEL_1X		0x00
+#define BU27008_GSEL_4X		0x08
+#define BU27008_GSEL_8X		0x09
+#define BU27008_GSEL_16X	0x0a
+#define BU27008_GSEL_32X	0x0b
+#define BU27008_GSEL_64X	0x0c
+#define BU27008_GSEL_256X	0x18
+#define BU27008_GSEL_512X	0x19
+#define BU27008_GSEL_1024X	0x1a
+
+static const struct iio_gain_sel_pair bu27008_gains[] = {
+	GAIN_SCALE_GAIN(1, BU27008_GSEL_1X),
+	GAIN_SCALE_GAIN(4, BU27008_GSEL_4X),
+	GAIN_SCALE_GAIN(8, BU27008_GSEL_8X),
+	GAIN_SCALE_GAIN(16, BU27008_GSEL_16X),
+	GAIN_SCALE_GAIN(32, BU27008_GSEL_32X),
+	GAIN_SCALE_GAIN(64, BU27008_GSEL_64X),
+	GAIN_SCALE_GAIN(256, BU27008_GSEL_256X),
+	GAIN_SCALE_GAIN(512, BU27008_GSEL_512X),
+	GAIN_SCALE_GAIN(1024, BU27008_GSEL_1024X),
+};
+
+static const struct iio_gain_sel_pair bu27008_gains_ir[] = {
+	GAIN_SCALE_GAIN(2, BU27008_GSEL_1X),
+	GAIN_SCALE_GAIN(4, BU27008_GSEL_4X),
+	GAIN_SCALE_GAIN(8, BU27008_GSEL_8X),
+	GAIN_SCALE_GAIN(16, BU27008_GSEL_16X),
+	GAIN_SCALE_GAIN(32, BU27008_GSEL_32X),
+	GAIN_SCALE_GAIN(64, BU27008_GSEL_64X),
+	GAIN_SCALE_GAIN(256, BU27008_GSEL_256X),
+	GAIN_SCALE_GAIN(512, BU27008_GSEL_512X),
+	GAIN_SCALE_GAIN(1024, BU27008_GSEL_1024X),
+};
+
+#define BU27008_MEAS_MODE_100MS		0x00
+#define BU27008_MEAS_MODE_55MS		0x01
+#define BU27008_MEAS_MODE_200MS		0x02
+#define BU27008_MEAS_MODE_400MS		0x04
+#define BU27008_MEAS_TIME_MAX_MS	400
+
+static const struct iio_itime_sel_mul bu27008_itimes[] = {
+	GAIN_SCALE_ITIME_US(400000, BU27008_MEAS_MODE_400MS, 8),
+	GAIN_SCALE_ITIME_US(200000, BU27008_MEAS_MODE_200MS, 4),
+	GAIN_SCALE_ITIME_US(100000, BU27008_MEAS_MODE_100MS, 2),
+	GAIN_SCALE_ITIME_US(55000, BU27008_MEAS_MODE_55MS, 1),
+};
+
+/*
+ * All the RGBC channels share the same gain.
+ * IR gain can be fine-tuned from the gain set for the RGBC by 2 bit, but this
+ * would yield quite complex gain setting. Especially since not all bit
+ * compinations are supported. And in any case setting GAIN for RGBC will
+ * always also change the IR-gain.
+ *
+ * On top of this, the selector '0' which corresponds to hw-gain 1X on RGBC,
+ * corresponds to gain 2X on IR. Rest of the selctors correspond to same gains
+ * though. This, however, makes it not possible to use shared gain for all
+ * RGBC and IR settings even though they are all changed at the one go.
+ */
+#define BU27008_CHAN(color, data, separate_avail)				\
+{										\
+	.type = IIO_INTENSITY,							\
+	.modified = 1,								\
+	.channel2 = IIO_MOD_LIGHT_##color,					\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |				\
+			      BIT(IIO_CHAN_INFO_SCALE),				\
+	.info_mask_separate_available = (separate_avail),			\
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),			\
+	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME),	\
+	.address = BU27008_REG_##data##_LO,					\
+	.scan_index = BU27008_##color,						\
+	.scan_type = {								\
+		.sign = 's',							\
+		.realbits = 16,							\
+		.storagebits = 16,						\
+		.endianness = IIO_LE,						\
+	},									\
+}
+
+/* For raw reads we always configure DATA3 for CLEAR */
+static const struct iio_chan_spec bu27008_channels[] = {
+	BU27008_CHAN(RED, DATA0, BIT(IIO_CHAN_INFO_SCALE)),
+	BU27008_CHAN(GREEN, DATA1, BIT(IIO_CHAN_INFO_SCALE)),
+	BU27008_CHAN(BLUE, DATA2, BIT(IIO_CHAN_INFO_SCALE)),
+	BU27008_CHAN(CLEAR, DATA2, BIT(IIO_CHAN_INFO_SCALE)),
+	/*
+	 * We don't allow setting scale for IR (because of shared gain bits).
+	 * Hence we don't advertise available ones either.
+	 */
+	BU27008_CHAN(IR, DATA3, 0),
+	IIO_CHAN_SOFT_TIMESTAMP(BU27008_NUM_CHANS),
+};
+
+struct bu27008_data {
+	struct regmap *regmap;
+	struct iio_trigger *trig;
+	struct device *dev;
+	struct iio_gts gts;
+	struct iio_gts gts_ir;
+	int irq;
+
+	/*
+	 * Prevent changing gain/time config when scale is read/written.
+	 * Similarly, protect the integration_time read/change sequence.
+	 * Prevent changing gain/time when data is read.
+	 */
+	struct mutex mutex;
+};
+
+static const struct regmap_range bu27008_volatile_ranges[] = {
+	{
+		.range_min = BU27008_REG_SYSTEM_CONTROL,	/* SWRESET */
+		.range_max = BU27008_REG_SYSTEM_CONTROL,
+	}, {
+		.range_min = BU27008_REG_MODE_CONTROL3,		/* VALID */
+		.range_max = BU27008_REG_MODE_CONTROL3,
+	}, {
+		.range_min = BU27008_REG_DATA0_LO,		/* DATA */
+		.range_max = BU27008_REG_DATA3_HI,
+	},
+};
+
+static const struct regmap_access_table bu27008_volatile_regs = {
+	.yes_ranges = &bu27008_volatile_ranges[0],
+	.n_yes_ranges = ARRAY_SIZE(bu27008_volatile_ranges),
+};
+
+static const struct regmap_range bu27008_read_only_ranges[] = {
+	{
+		.range_min = BU27008_REG_DATA0_LO,
+		.range_max = BU27008_REG_DATA3_HI,
+	}, {
+		.range_min = BU27008_REG_MANUFACTURER_ID,
+		.range_max = BU27008_REG_MANUFACTURER_ID,
+	}
+};
+
+static const struct regmap_access_table bu27008_ro_regs = {
+	.no_ranges = &bu27008_read_only_ranges[0],
+	.n_no_ranges = ARRAY_SIZE(bu27008_read_only_ranges),
+};
+
+static const struct regmap_config bu27008_regmap = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = BU27008_REG_MAX,
+	.cache_type = REGCACHE_RBTREE,
+	.volatile_table = &bu27008_volatile_regs,
+	.wr_table = &bu27008_ro_regs,
+};
+
+#define BU27008_MAX_VALID_RESULT_WAIT_US	50000
+#define BU27008_VALID_RESULT_WAIT_QUANTA_US	1000
+
+static int bu27008_chan_read_data(struct bu27008_data *data, int reg, int *val)
+{
+	int ret, valid;
+	__le16 tmp;
+
+	ret = regmap_read_poll_timeout(data->regmap, BU27008_REG_MODE_CONTROL3,
+				       valid, (valid & BU27008_MASK_VALID),
+				       BU27008_VALID_RESULT_WAIT_QUANTA_US,
+				       BU27008_MAX_VALID_RESULT_WAIT_US);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, reg, &tmp, sizeof(tmp));
+	if (ret)
+		dev_err(data->dev, "Reading channel data failed\n");
+
+	*val = le16_to_cpu(tmp);
+
+	return ret;
+}
+
+static int bu27008_get_gain(struct bu27008_data *data, struct iio_gts *gts, int *gain)
+{
+	int ret, sel;
+
+	ret = regmap_read(data->regmap, BU27008_REG_MODE_CONTROL2, &sel);
+	if (ret)
+		return ret;
+
+	sel = FIELD_GET(BU27008_MASK_RGBC_GAIN, sel);
+
+	ret = iio_gts_find_gain_by_sel(gts, sel);
+	if (ret < 0) {
+		dev_err(data->dev, "unknown gain value 0x%x\n", sel);
+		return ret;
+	}
+
+	*gain = ret;
+
+	return 0;
+}
+
+static int bu27008_write_gain_sel(struct bu27008_data *data, int sel)
+{
+	int regval;
+
+	regval = FIELD_PREP(BU27008_MASK_RGBC_GAIN, sel);
+
+	/*
+	 * We do always set also the LOW bits of IR-gain because othervice we
+	 * would risk resulting an invalid GAIN register value.
+	 *
+	 * We could allow setting separate gains for RGBC and IR when the
+	 * values were such that HW could support both gain settings.
+	 * Eg, when the shared bits were same for both gain values.
+	 *
+	 * This, however, has a negligible benefit compared to the increased
+	 * software complexity when we would need to go through the gains
+	 * for both channels separately when the integration time changes.
+	 * This would end up with nasty logic for computing gain values for
+	 * both channels - and rejecting them if shared bits changed.
+	 *
+	 * We should then build the logic by guessing what a user prefers.
+	 * RGBC or IR gains correctly set while other jumps to odd value?
+	 * Maybe look-up a value where both gains are somehow optimized
+	 * <what this somehow is, is ATM unknown to us>. Or maybe user would
+	 * expect us to reject changes when optimal gains can't be set to both
+	 * channels w/given integration time. At best that would result
+	 * solution that works well for a very specific subset of
+	 * configurations but causes unexpected corner-cases.
+	 *
+	 * So, we keep it simple. Always set same selector to IR and RGBC.
+	 * We disallow setting IR (as I expect that most of the users are
+	 * interested in RGBC). This way we can show the user that the scales
+	 * for RGBC and IR channels are different (1X Vs 2X with sel 0) while
+	 * still keeping the operation deterministic.
+	 */
+	regval |= FIELD_PREP(BU27008_MASK_IR_GAIN_LO, sel);
+
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL2,
+				  BU27008_MASK_RGBC_GAIN, regval);
+}
+
+static int bu27008_set_gain(struct bu27008_data *data, int gain)
+{
+	int ret;
+
+	ret = iio_gts_find_sel_by_gain(&data->gts, gain);
+	if (ret < 0)
+		return ret;
+
+	return bu27008_write_gain_sel(data, ret);
+}
+
+static int bu27008_get_int_time_sel(struct bu27008_data *data, int *sel)
+{
+	int ret, val;
+
+	ret = regmap_read(data->regmap, BU27008_REG_MODE_CONTROL1, &val);
+	*sel = FIELD_GET(BU27008_MASK_MEAS_MODE, val);
+
+	return ret;
+}
+
+static int bu27008_set_int_time_sel(struct bu27008_data *data, int sel)
+{
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL1,
+				  BU27008_MASK_MEAS_MODE, sel);
+}
+
+static int bu27008_get_int_time_us(struct bu27008_data *data)
+{
+	int ret, sel;
+
+	ret = bu27008_get_int_time_sel(data, &sel);
+	if (ret)
+		return ret;
+
+	return iio_gts_find_int_time_by_sel(&data->gts, sel);
+}
+
+static int _bu27008_get_scale(struct bu27008_data *data, bool ir, int *val,
+			      int *val2)
+{
+	struct iio_gts *gts;
+	int gain, ret;
+
+	if (ir)
+		gts = &data->gts_ir;
+	else
+		gts = &data->gts;
+
+	ret = bu27008_get_gain(data, gts, &gain);
+	if (ret)
+		return ret;
+
+	ret = bu27008_get_int_time_us(data);
+	if (ret < 0)
+		return ret;
+
+	return iio_gts_get_scale(gts, gain, ret, val, val2);
+}
+
+static int bu27008_get_scale(struct bu27008_data *data, bool ir, int *val,
+			     int *val2)
+{
+	int ret;
+
+	mutex_lock(&data->mutex);
+	ret = _bu27008_get_scale(data, ir, val, val2);
+	mutex_unlock(&data->mutex);
+
+	return ret;
+}
+
+static int bu27008_set_int_time(struct bu27008_data *data, int time)
+{
+	int ret;
+
+	ret = iio_gts_find_sel_by_int_time(&data->gts, time);
+	if (ret < 0)
+		return ret;
+
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL1,
+				  BU27008_MASK_MEAS_MODE, ret);
+}
+
+/* Try to change the time so that the scale is maintained */
+static int bu27008_try_set_int_time(struct bu27008_data *data, int int_time_new)
+{
+	int ret, old_time_sel, new_time_sel,  old_gain, new_gain;
+
+	mutex_lock(&data->mutex);
+
+	ret = bu27008_get_int_time_sel(data, &old_time_sel);
+	if (ret < 0)
+		goto unlock_out;
+
+	if (!iio_gts_valid_time(&data->gts, int_time_new)) {
+		dev_dbg(data->dev, "Unsupported integration time %u\n",
+			int_time_new);
+
+		ret = -EINVAL;
+		goto unlock_out;
+	}
+
+	/* If we already use requested time, then we're done */
+	new_time_sel = iio_gts_find_sel_by_int_time(&data->gts, int_time_new);
+	if (new_time_sel == old_time_sel)
+		goto unlock_out;
+
+	ret = bu27008_get_gain(data, &data->gts, &old_gain);
+	if (ret)
+		goto unlock_out;
+
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&data->gts, old_gain,
+				old_time_sel, new_time_sel, &new_gain);
+	if (ret) {
+		int scale1, scale2;
+		bool ok;
+
+		_bu27008_get_scale(data, false, &scale1, &scale2);
+		dev_dbg(data->dev,
+			"Can't support time %u with current scale %u %u\n",
+			int_time_new, scale1, scale2);
+
+		if (new_gain < 0)
+			goto unlock_out;
+
+		/*
+		 * If caller requests for integration time change and we
+		 * can't support the scale - then the caller should be
+		 * prepared to 'pick up the pieces and deal with the
+		 * fact that the scale changed'.
+		 */
+		ret = iio_find_closest_gain_low(&data->gts, new_gain, &ok);
+		if (!ok)
+			dev_dbg(data->dev, "optimal gain out of range\n");
+
+		if (ret < 0) {
+			dev_dbg(data->dev,
+				 "Total gain increase. Risk of saturation");
+			ret = iio_gts_get_min_gain(&data->gts);
+			if (ret < 0)
+				goto unlock_out;
+		}
+		new_gain = ret;
+		dev_dbg(data->dev, "scale changed, new gain %u\n", new_gain);
+	}
+
+	ret = bu27008_set_gain(data, new_gain);
+	if (ret)
+		goto unlock_out;
+
+	ret = bu27008_set_int_time(data, int_time_new);
+
+unlock_out:
+	mutex_unlock(&data->mutex);
+
+	return ret;
+}
+
+static int bu27008_meas_set(struct bu27008_data *data, int state)
+{
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				  BU27008_MASK_MEAS_EN, state);
+}
+
+static int bu27008_chan_cfg(struct bu27008_data *data,
+			    struct iio_chan_spec const *chan)
+{
+	int chan_sel;
+
+	if (chan->scan_index == BU27008_BLUE)
+		chan_sel = BU27008_BLUE2_CLEAR3;
+	else
+		chan_sel = BU27008_CLEAR2_IR3;
+
+	chan_sel = FIELD_PREP(BU27008_MASK_CHAN_SEL, chan_sel);
+
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				  BU27008_MASK_CHAN_SEL, chan_sel);
+}
+
+static int bu27008_read_one(struct bu27008_data *data, struct iio_dev *idev,
+			    struct iio_chan_spec const *chan, int *val, int *val2)
+{
+	int ret, int_time;
+
+	ret = bu27008_chan_cfg(data, chan);
+	if (ret)
+		return ret;
+
+	ret = bu27008_meas_set(data, BU27008_MEAS_EN);
+	if (ret)
+		return ret;
+
+	int_time = bu27008_get_int_time_us(data);
+	if (int_time < 0)
+		int_time = BU27008_MEAS_TIME_MAX_MS;
+	else
+		int_time /= USEC_PER_MSEC;
+
+	msleep(int_time);
+
+	ret = bu27008_chan_read_data(data, chan->address, val);
+	if (!ret)
+		ret = IIO_VAL_INT;
+
+	if (bu27008_meas_set(data, BU27008_MEAS_DIS))
+		dev_warn(data->dev, "measurement disabling failed\n");
+
+	return ret;
+}
+
+static int bu27008_read_raw(struct iio_dev *idev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct bu27008_data *data = iio_priv(idev);
+	int busy, ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+	{
+		busy = iio_device_claim_direct_mode(idev);
+		if (busy)
+			return -EBUSY;
+
+		mutex_lock(&data->mutex);
+		ret = bu27008_read_one(data, idev, chan, val, val2);
+		mutex_unlock(&data->mutex);
+
+		iio_device_release_direct_mode(idev);
+
+		return ret;
+	}
+	case IIO_CHAN_INFO_SCALE:
+		ret = bu27008_get_scale(data, chan->scan_index == BU27008_IR,
+					val, val2);
+		if (ret)
+			return ret;
+
+		return IIO_VAL_INT_PLUS_NANO;
+
+	case IIO_CHAN_INFO_INT_TIME:
+		ret = bu27008_get_int_time_us(data);
+		if (ret < 0)
+			return ret;
+
+		*val = 0;
+		*val2 = ret;
+
+		return IIO_VAL_INT_PLUS_MICRO;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+/* Called if the new scale could not be supported with existing int-time */
+static int bu27008_try_find_new_time_gain(struct bu27008_data *data, int val,
+					  int val2, int *gain_sel)
+{
+	int i, ret, new_time_sel;
+
+	for (i = 0; i < data->gts.num_itime; i++) {
+		new_time_sel = data->gts.itime_table[i].sel;
+		ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts,
+					new_time_sel, val, val2 * 1000, gain_sel);
+		if (!ret)
+			break;
+	}
+	if (i == data->gts.num_itime) {
+		dev_err(data->dev, "Can't support scale %u %u\n", val, val2);
+
+		return -EINVAL;
+	}
+
+	return bu27008_set_int_time_sel(data, new_time_sel);
+}
+
+static int bu27008_set_scale(struct bu27008_data *data,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2)
+{
+	int ret, gain_sel, time_sel;
+
+	if (chan->scan_index == BU27008_IR)
+		return -EINVAL;
+
+	mutex_lock(&data->mutex);
+
+	ret = bu27008_get_int_time_sel(data, &time_sel);
+	if (ret < 0)
+		goto unlock_out;
+
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts, time_sel,
+						val, val2 * 1000, &gain_sel);
+	if (ret) {
+		ret = bu27008_try_find_new_time_gain(data, val, val2, &gain_sel);
+		if (ret)
+			goto unlock_out;
+
+	}
+	ret = bu27008_write_gain_sel(data, gain_sel);
+
+unlock_out:
+	mutex_unlock(&data->mutex);
+
+	return ret;
+}
+
+static int bu27008_write_raw(struct iio_dev *idev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	struct bu27008_data *data = iio_priv(idev);
+	int ret;
+
+	/*
+	 * Do not allow changing scale when measurement is ongoing as doing so
+	 * could make values in the buffer inconsistent.
+	 */
+	ret = iio_device_claim_direct_mode(idev);
+	if (ret)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		ret = bu27008_set_scale(data, chan, val, val2);
+		break;
+	case IIO_CHAN_INFO_INT_TIME:
+		if (val)
+			ret = -EINVAL;
+		else
+			ret = bu27008_try_set_int_time(data, val2);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	iio_device_release_direct_mode(idev);
+
+	return ret;
+}
+
+static int bu27008_read_avail(struct iio_dev *idev,
+			      struct iio_chan_spec const *chan, const int **vals,
+			      int *type, int *length, long mask)
+{
+	struct bu27008_data *data = iio_priv(idev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_INT_TIME:
+		return iio_gts_avail_times(&data->gts, vals, type, length);
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->channel2 == IIO_MOD_LIGHT_IR)
+			return iio_gts_all_avail_scales(&data->gts_ir, vals,
+							type, length);
+		return iio_gts_all_avail_scales(&data->gts, vals, type, length);
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info bu27008_info = {
+	.read_raw = &bu27008_read_raw,
+	.write_raw = &bu27008_write_raw,
+	.read_avail = &bu27008_read_avail,
+	.validate_trigger = iio_validate_own_trigger,
+};
+
+static int bu27008_chip_init(struct bu27008_data *data)
+{
+	int ret;
+
+	ret = regmap_write_bits(data->regmap, BU27008_REG_SYSTEM_CONTROL,
+				BU27008_MASK_SW_RESET, BU27008_MASK_SW_RESET);
+	if (ret)
+		return dev_err_probe(data->dev, ret, "Sensor reset failed\n");
+
+	/*
+	 * The data-sheet does not tell how long performing the IC reset takes.
+	 * However, the data-sheet says the minimum time it takes the IC to be
+	 * able to take inputs after power is applied, is 100 uS. I'd assume
+	 * > 1 mS is enough.
+	 */
+	msleep(1);
+
+	ret = regmap_reinit_cache(data->regmap, &bu27008_regmap);
+	if (ret) {
+		dev_err(data->dev, "Failed to reinit reg cache\n");
+		return ret;
+	}
+
+	return ret;
+}
+
+static int bu27008_set_drdy_irq(struct bu27008_data *data, int state)
+{
+	return regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				 BU27008_MASK_INT_EN, state);
+}
+
+static int bu27008_trigger_set_state(struct iio_trigger *trig,
+				     bool state)
+{
+	struct bu27008_data *data = iio_trigger_get_drvdata(trig);
+	int ret = 0;
+
+	if (state)
+		ret = bu27008_set_drdy_irq(data, BU27008_INT_EN);
+	else
+		ret = bu27008_set_drdy_irq(data, BU27008_INT_DIS);
+	if (ret)
+		dev_err(data->dev, "Failed to set trigger state\n");
+
+	return ret;
+}
+
+static const struct iio_trigger_ops bu27008_trigger_ops = {
+	.set_trigger_state = bu27008_trigger_set_state,
+};
+
+static irqreturn_t bu27008_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *idev = pf->indio_dev;
+	struct bu27008_data *data = iio_priv(idev);
+	struct {
+		__le16 chan[BU27008_NUM_HW_CHANS];
+		s64 ts __aligned(8);
+	} raw;
+	int ret, dummy;
+
+	memset(&raw, 0, sizeof(raw));
+
+	/*
+	 * After some measurements, it seems reading the
+	 * BU27008_REG_MODE_CONTROL3 debounces the IRQ line
+	 */
+	ret = regmap_read(data->regmap, BU27008_REG_MODE_CONTROL3, &dummy);
+	if (ret < 0)
+		goto err_read;
+
+	ret = regmap_bulk_read(data->regmap, BU27008_REG_DATA0_LO, &raw.chan,
+			       sizeof(raw.chan));
+	if (ret < 0)
+		goto err_read;
+
+	iio_push_to_buffers_with_timestamp(idev, &raw, pf->timestamp);
+err_read:
+	iio_trigger_notify_done(idev->trig);
+
+	enable_irq(data->irq);
+
+	return IRQ_HANDLED;
+}
+
+static int bu27008_buffer_preenable(struct iio_dev *idev)
+{
+	struct bu27008_data *data = iio_priv(idev);
+	int chan_sel, ret;
+
+	/* Configure channel selection */
+	if (test_bit(BU27008_BLUE, idev->active_scan_mask)) {
+		if (test_bit(BU27008_CLEAR, idev->active_scan_mask))
+			chan_sel = BU27008_BLUE2_CLEAR3;
+		else
+			chan_sel = BU27008_BLUE2_IR3;
+	} else {
+		chan_sel = BU27008_CLEAR2_IR3;
+	}
+
+	chan_sel = FIELD_PREP(BU27008_MASK_CHAN_SEL, chan_sel);
+
+	ret = regmap_update_bits(data->regmap, BU27008_REG_MODE_CONTROL3,
+				 BU27008_MASK_CHAN_SEL, chan_sel);
+	if (ret)
+		return ret;
+
+	return bu27008_meas_set(data, BU27008_MEAS_EN);
+}
+
+static int bu27008_buffer_postdisable(struct iio_dev *idev)
+{
+	struct bu27008_data *data = iio_priv(idev);
+
+	return bu27008_meas_set(data, BU27008_MEAS_DIS);
+}
+
+static const struct iio_buffer_setup_ops bu27008_buffer_ops = {
+	.preenable = bu27008_buffer_preenable,
+	.postdisable = bu27008_buffer_postdisable,
+};
+
+static irqreturn_t bu27008_data_rdy_poll(int irq, void *private)
+{
+	/*
+	 * The BU27008 keeps IRQ asserted until we read the VALID bit from
+	 * a register. We need to keep the IRQ disabled until this
+	 */
+	disable_irq_nosync(irq);
+	iio_trigger_poll(private);
+
+	return IRQ_HANDLED;
+}
+
+static int bu27008_probe(struct i2c_client *i2c)
+{
+	struct device *dev = &i2c->dev;
+	struct iio_trigger *itrig;
+	struct bu27008_data *data;
+	struct regmap *regmap;
+	unsigned int part_id, reg;
+	struct iio_dev *idev;
+	char *name;
+	int ret;
+
+	regmap = devm_regmap_init_i2c(i2c, &bu27008_regmap);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "Failed to initialize Regmap\n");
+
+	idev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!idev)
+		return -ENOMEM;
+
+	ret = devm_regulator_get_enable(dev, "vdd");
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to get regulator\n");
+
+	data = iio_priv(idev);
+
+	ret = regmap_read(regmap, BU27008_REG_SYSTEM_CONTROL, &reg);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to access sensor\n");
+
+	part_id = FIELD_GET(BU27008_MASK_PART_ID, reg);
+
+	if (part_id != BU27008_ID)
+		dev_warn(dev, "unknown device 0x%x\n", part_id);
+
+	ret = devm_iio_init_iio_gts(dev, BU27008_SCALE_1X, 0, bu27008_gains,
+				    ARRAY_SIZE(bu27008_gains), bu27008_itimes,
+				    ARRAY_SIZE(bu27008_itimes), &data->gts);
+	if (ret)
+		return ret;
+
+	ret = devm_iio_init_iio_gts(dev, BU27008_SCALE_1X, 0, bu27008_gains_ir,
+				    ARRAY_SIZE(bu27008_gains_ir), bu27008_itimes,
+				    ARRAY_SIZE(bu27008_itimes), &data->gts_ir);
+	if (ret)
+		return ret;
+
+	mutex_init(&data->mutex);
+	data->regmap = regmap;
+	data->dev = dev;
+	data->irq = i2c->irq;
+
+	idev->channels = bu27008_channels;
+	idev->num_channels = ARRAY_SIZE(bu27008_channels);
+	idev->name = "bu27008";
+	idev->info = &bu27008_info;
+	idev->modes = INDIO_DIRECT_MODE;
+	idev->available_scan_masks = bu27008_scan_masks;
+
+	ret = bu27008_chip_init(data);
+	if (ret)
+		return ret;
+
+	if (i2c->irq) {
+		ret = devm_iio_triggered_buffer_setup(dev, idev,
+						      &iio_pollfunc_store_time,
+						      bu27008_trigger_handler,
+						      &bu27008_buffer_ops);
+		if (ret)
+			return dev_err_probe(dev, ret,
+				     "iio_triggered_buffer_setup_ext FAIL\n");
+
+		itrig = devm_iio_trigger_alloc(dev, "%sdata-rdy-dev%d",
+					       idev->name, iio_device_id(idev));
+		if (!itrig)
+			return -ENOMEM;
+
+		data->trig = itrig;
+
+		itrig->ops = &bu27008_trigger_ops;
+		iio_trigger_set_drvdata(itrig, data);
+
+		name = devm_kasprintf(dev, GFP_KERNEL, "%s-bu27008",
+				      dev_name(dev));
+
+		ret = devm_request_irq(dev, i2c->irq,
+				       &bu27008_data_rdy_poll,
+				       0, name, itrig);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "Could not request IRQ\n");
+
+		ret = devm_iio_trigger_register(dev, itrig);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "Trigger registration failed\n");
+
+		/* set default trigger */
+		idev->trig = iio_trigger_get(itrig);
+	} else {
+		dev_info(dev, "No IRQ, buffered mode disabled\n");
+	}
+
+	ret = devm_iio_device_register(dev, idev);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Unable to register iio device\n");
+
+	return 0;
+}
+
+static const struct of_device_id bu27008_of_match[] = {
+	{ .compatible = "rohm,bu27008" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, bu27008_of_match);
+
+static struct i2c_driver bu27008_i2c_driver = {
+	.driver = {
+		.name = "bu27008",
+		.of_match_table = bu27008_of_match,
+	},
+	.probe_new = bu27008_probe,
+};
+module_i2c_driver(bu27008_i2c_driver);
+
+MODULE_DESCRIPTION("ROHM BU27008 colour sensor driver");
+MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(IIO_GTS_HELPER);