From: Vasileios Amoiridis <vassilisamir@gmail.com>

Add triggered buffer and soft timestamp support. The available scan mask
enables all the channels of the sensor in order to follow the operation of
the sensor. The sensor basically starts to capture from all channels
as long as it enters into FORCED mode.

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
---
 drivers/iio/chemical/Kconfig       |   2 +
 drivers/iio/chemical/bme680.h      |   2 +
 drivers/iio/chemical/bme680_core.c | 168 ++++++++++++++++++++++++++++-
 3 files changed, 171 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/chemical/Kconfig b/drivers/iio/chemical/Kconfig
index 678a6adb9a75..447b205f57bd 100644
--- a/drivers/iio/chemical/Kconfig
+++ b/drivers/iio/chemical/Kconfig
@@ -50,6 +50,8 @@ config BME680
 	select REGMAP
 	select BME680_I2C if I2C
 	select BME680_SPI if SPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Say yes here to build support for Bosch Sensortec BME680 sensor with
 	  temperature, pressure, humidity and gas sensing capability.
diff --git a/drivers/iio/chemical/bme680.h b/drivers/iio/chemical/bme680.h
index 95d39c154d59..e7eed2962baa 100644
--- a/drivers/iio/chemical/bme680.h
+++ b/drivers/iio/chemical/bme680.h
@@ -64,6 +64,8 @@
 
 #define BME680_STARTUP_TIME_US			2000
 
+#define BME680_NUM_CHANNELS			4
+
 /* Calibration Parameters */
 #define BME680_T2_LSB_REG	0x8A
 #define BME680_H2_MSB_REG	0xE1
diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index 7d6f4d8c5fe4..df6ae4355902 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -18,8 +18,11 @@
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 
+#include <linux/iio/buffer.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
 
 #include <asm/unaligned.h>
 
@@ -108,6 +111,13 @@ static const char *const bme680_supply_names[] = {
 
 #define BME680_NUM_SUPPLIES ARRAY_SIZE(bme680_supply_names)
 
+enum bme680_scan {
+	BME680_TEMP,
+	BME680_PRESS,
+	BME680_HUMID,
+	BME680_GAS,
+};
+
 struct bme680_data {
 	struct regmap *regmap;
 	struct bme680_calib bme680;
@@ -122,8 +132,11 @@ struct bme680_data {
 	struct regulator_bulk_data supplies[BME680_NUM_SUPPLIES];
 	int ambient_temp;
 
+	u8 buffer[ALIGN(sizeof(s32) * BME680_NUM_CHANNELS, sizeof(s64))
+		  + sizeof(s64)] __aligned(sizeof(s64));
+
 	union {
-		u8 buf[3];
+		u8 buf[15];
 		unsigned int check;
 		__be16 be16;
 		u8 bme680_cal_buf_1[BME680_CALIB_RANGE_1_LEN];
@@ -160,6 +173,13 @@ static const struct iio_chan_spec bme680_channels[] = {
 				      BIT(IIO_CHAN_INFO_RAW) |
 				      BIT(IIO_CHAN_INFO_SCALE) |
 				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 16,
+			.storagebits = 16,
+			.endianness = IIO_CPU,
+		},
 	},
 	{
 		.type = IIO_PRESSURE,
@@ -168,6 +188,13 @@ static const struct iio_chan_spec bme680_channels[] = {
 				      BIT(IIO_CHAN_INFO_RAW) |
 				      BIT(IIO_CHAN_INFO_SCALE) |
 				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
 	},
 	{
 		.type = IIO_HUMIDITYRELATIVE,
@@ -176,11 +203,26 @@ static const struct iio_chan_spec bme680_channels[] = {
 				      BIT(IIO_CHAN_INFO_RAW) |
 				      BIT(IIO_CHAN_INFO_SCALE) |
 				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+		.scan_index = 2,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
 	},
 	{
 		.type = IIO_RESISTANCE,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+		.scan_index = 3,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
 	},
+	IIO_CHAN_SOFT_TIMESTAMP(4),
 };
 
 static int bme680_read_calib(struct bme680_data *data,
@@ -997,6 +1039,121 @@ static const struct iio_info bme680_info = {
 	.attrs = &bme680_attribute_group,
 };
 
+static const unsigned long bme680_avail_scan_masks[] = {
+	BIT(BME680_GAS) | BIT(BME680_HUMID) | BIT(BME680_PRESS) | BIT(BME680_TEMP),
+	0
+};
+
+static irqreturn_t bme680_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct bme680_data *data = iio_priv(indio_dev);
+	u32 adc_temp, adc_press, adc_humid, comp_press, comp_humid;
+	s32 *chans = (s32 *)data->buffer;
+	u16 adc_gas_res, gas_regs_val;
+	s32 t_fine, comp_gas_res;
+	s16 comp_temp;
+	u8 gas_range;
+	int ret;
+
+	guard(mutex)(&data->lock);
+
+	ret = bme680_set_mode(data, BME680_FORCED);
+	if (ret < 0)
+		goto out;
+
+	ret = bme680_wait_for_eoc(data);
+	if (ret)
+		goto out;
+
+	/* Burst read data regs */
+	ret = regmap_bulk_read(data->regmap, BME680_REG_MEAS_STAT_0,
+			       data->buf, sizeof(data->buf));
+	if (ret) {
+		dev_err(data->dev, "failed to burst read sensor data\n");
+		goto out;
+	}
+	if (data->buf[0] & BME680_GAS_MEAS_BIT) {
+		dev_err(data->dev, "gas measurement incomplete\n");
+		goto out;
+	}
+
+	/* Temperature calculations */
+	adc_temp = FIELD_GET(BME680_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[5]));
+	if (adc_temp == BME680_MEAS_SKIPPED) {
+		dev_err(data->dev, "reading temperature skipped\n");
+		goto out;
+	}
+	comp_temp = bme680_compensate_temp(data, adc_temp);
+	t_fine = bme680_calc_t_fine(data, adc_temp);
+
+	/* Pressure calculations */
+	adc_press = FIELD_GET(BME680_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[2]));
+	if (adc_press == BME680_MEAS_SKIPPED) {
+		dev_err(data->dev, "reading pressure skipped\n");
+		goto out;
+	}
+	comp_press = bme680_compensate_press(data, adc_press, t_fine);
+	pr_info("comp_press: %d\n", comp_press);
+
+	/* Humidity calculations */
+	adc_humid = get_unaligned_be16(&data->buf[8]);
+	if (adc_humid == BME680_MEAS_SKIPPED) {
+		dev_err(data->dev, "reading humidity skipped\n");
+		goto out;
+	}
+	comp_humid = bme680_compensate_humid(data, adc_humid, t_fine);
+	pr_info("comp_humid: %d\n", comp_humid);
+
+	/* Gas calculations */
+	gas_regs_val = get_unaligned_be16(&data->buf[13]);
+	adc_gas_res = FIELD_GET(BME680_ADC_GAS_RES, gas_regs_val);
+	if ((gas_regs_val & BME680_GAS_STAB_BIT) == 0) {
+		dev_err(data->dev, "heater failed to reach the target temperature\n");
+		goto out;
+	}
+	gas_range = FIELD_GET(BME680_GAS_RANGE_MASK, gas_regs_val);
+	comp_gas_res = bme680_compensate_gas(data, adc_gas_res, gas_range);
+	pr_info("comp_gas_res: %d\n", comp_gas_res);
+
+	chans[0] = comp_temp;
+	chans[1] = comp_press;
+	chans[2] = comp_humid;
+	chans[3] = comp_gas_res;
+
+	/* Push to buffer */
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
+					   iio_get_time_ns(indio_dev));
+out:
+	iio_trigger_notify_done(indio_dev->trig);
+	return IRQ_HANDLED;
+}
+
+static int bme680_buffer_preenable(struct iio_dev *indio_dev)
+{
+	struct bme680_data *data = iio_priv(indio_dev);
+
+	pm_runtime_get_sync(data->dev);
+
+	return 0;
+}
+
+static int bme680_buffer_postdisable(struct iio_dev *indio_dev)
+{
+	struct bme680_data *data = iio_priv(indio_dev);
+
+	pm_runtime_mark_last_busy(data->dev);
+	pm_runtime_put_autosuspend(data->dev);
+
+	return 0;
+}
+
+static const struct iio_buffer_setup_ops bme680_buffer_setup_ops = {
+	.preenable = bme680_buffer_preenable,
+	.postdisable = bme680_buffer_postdisable,
+};
+
 static void bme680_regulators_disable(void *data)
 {
 	struct regulator_bulk_data *supplies = data;
@@ -1032,6 +1189,7 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
 	indio_dev->name = name;
 	indio_dev->channels = bme680_channels;
 	indio_dev->num_channels = ARRAY_SIZE(bme680_channels);
+	indio_dev->available_scan_masks = bme680_avail_scan_masks;
 	indio_dev->info = &bme680_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
@@ -1088,6 +1246,14 @@ int bme680_core_probe(struct device *dev, struct regmap *regmap,
 		return dev_err_probe(dev, ret,
 				     "failed to set gas config data\n");
 
+	ret = devm_iio_triggered_buffer_setup(data->dev, indio_dev,
+					      iio_pollfunc_store_time,
+					      bme680_trigger_handler,
+					      &bme680_buffer_setup_ops);
+	if (ret)
+		return dev_err_probe(data->dev, ret,
+				     "iio triggered buffer setup failed\n");
+
 	/* Enable runtime PM */
 	pm_runtime_get_noresume(dev);
 	pm_runtime_set_active(dev);
-- 
2.43.0

On Thu, Oct 10, 2024 at 11:00:29PM +0200, vamoirid wrote:
> From: Vasileios Amoiridis <vassilisamir@gmail.com>
> 
> Add triggered buffer and soft timestamp support. The available scan mask
> enables all the channels of the sensor in order to follow the operation of
> the sensor. The sensor basically starts to capture from all channels
> as long as it enters into FORCED mode.

...

>  	struct regulator_bulk_data supplies[BME680_NUM_SUPPLIES];
>  	int ambient_temp;
>  
> +	u8 buffer[ALIGN(sizeof(s32) * BME680_NUM_CHANNELS, sizeof(s64))
> +		  + sizeof(s64)] __aligned(sizeof(s64));

Can it be represented as a structure?
We also have aligned_s64 for the timestamp.

>  	union {
> -		u8 buf[3];
> +		u8 buf[15];
>  		unsigned int check;
>  		__be16 be16;
>  		u8 bme680_cal_buf_1[BME680_CALIB_RANGE_1_LEN];

...

> +static irqreturn_t bme680_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct bme680_data *data = iio_priv(indio_dev);
> +	u32 adc_temp, adc_press, adc_humid, comp_press, comp_humid;

> +	s32 *chans = (s32 *)data->buffer;

With the structure in place this becomes much more readable.

> +	u16 adc_gas_res, gas_regs_val;
> +	s32 t_fine, comp_gas_res;
> +	s16 comp_temp;
> +	u8 gas_range;
> +	int ret;
> +
> +	guard(mutex)(&data->lock);
> +
> +	ret = bme680_set_mode(data, BME680_FORCED);
> +	if (ret < 0)
> +		goto out;
> +
> +	ret = bme680_wait_for_eoc(data);
> +	if (ret)
> +		goto out;
> +
> +	/* Burst read data regs */
> +	ret = regmap_bulk_read(data->regmap, BME680_REG_MEAS_STAT_0,
> +			       data->buf, sizeof(data->buf));
> +	if (ret) {
> +		dev_err(data->dev, "failed to burst read sensor data\n");
> +		goto out;
> +	}
> +	if (data->buf[0] & BME680_GAS_MEAS_BIT) {
> +		dev_err(data->dev, "gas measurement incomplete\n");
> +		goto out;
> +	}
> +
> +	/* Temperature calculations */
> +	adc_temp = FIELD_GET(BME680_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[5]));
> +	if (adc_temp == BME680_MEAS_SKIPPED) {
> +		dev_err(data->dev, "reading temperature skipped\n");
> +		goto out;
> +	}
> +	comp_temp = bme680_compensate_temp(data, adc_temp);
> +	t_fine = bme680_calc_t_fine(data, adc_temp);
> +
> +	/* Pressure calculations */
> +	adc_press = FIELD_GET(BME680_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[2]));
> +	if (adc_press == BME680_MEAS_SKIPPED) {
> +		dev_err(data->dev, "reading pressure skipped\n");
> +		goto out;
> +	}
> +	comp_press = bme680_compensate_press(data, adc_press, t_fine);

> +	pr_info("comp_press: %d\n", comp_press);

No debugging in the production code. Or if you really need that, it should
use dev_dbg().

> +	/* Humidity calculations */
> +	adc_humid = get_unaligned_be16(&data->buf[8]);
> +	if (adc_humid == BME680_MEAS_SKIPPED) {
> +		dev_err(data->dev, "reading humidity skipped\n");
> +		goto out;
> +	}
> +	comp_humid = bme680_compensate_humid(data, adc_humid, t_fine);

> +	pr_info("comp_humid: %d\n", comp_humid);

Ditto.

> +
> +	/* Gas calculations */
> +	gas_regs_val = get_unaligned_be16(&data->buf[13]);
> +	adc_gas_res = FIELD_GET(BME680_ADC_GAS_RES, gas_regs_val);
> +	if ((gas_regs_val & BME680_GAS_STAB_BIT) == 0) {
> +		dev_err(data->dev, "heater failed to reach the target temperature\n");
> +		goto out;
> +	}
> +	gas_range = FIELD_GET(BME680_GAS_RANGE_MASK, gas_regs_val);
> +	comp_gas_res = bme680_compensate_gas(data, adc_gas_res, gas_range);
> +	pr_info("comp_gas_res: %d\n", comp_gas_res);
> +
> +	chans[0] = comp_temp;
> +	chans[1] = comp_press;
> +	chans[2] = comp_humid;
> +	chans[3] = comp_gas_res;
> +
> +	/* Push to buffer */
> +	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> +					   iio_get_time_ns(indio_dev));
> +out:
> +	iio_trigger_notify_done(indio_dev->trig);
> +	return IRQ_HANDLED;
> +}

-- 
With Best Regards,
Andy Shevchenko

On Fri, Oct 11, 2024 at 01:37:56PM +0300, Andy Shevchenko wrote:
> On Thu, Oct 10, 2024 at 11:00:29PM +0200, vamoirid wrote:
> > From: Vasileios Amoiridis <vassilisamir@gmail.com>
> > 
> > Add triggered buffer and soft timestamp support. The available scan mask
> > enables all the channels of the sensor in order to follow the operation of
> > the sensor. The sensor basically starts to capture from all channels
> > as long as it enters into FORCED mode.
> 
> ...
> 
> >  	struct regulator_bulk_data supplies[BME680_NUM_SUPPLIES];
> >  	int ambient_temp;
> >  
> > +	u8 buffer[ALIGN(sizeof(s32) * BME680_NUM_CHANNELS, sizeof(s64))
> > +		  + sizeof(s64)] __aligned(sizeof(s64));
> 
> Can it be represented as a structure?
> We also have aligned_s64 for the timestamp.
>

Hi Andy,

The same approach was used also for the bmp280 driver and since I was
working on the bmp280 as well, I did it here. You think the
representation as a struct would look better? Personally I like the
nature of this one because of the ALIGN() but I have no problem of using
a struct here.

> >  	union {
> > -		u8 buf[3];
> > +		u8 buf[15];
> >  		unsigned int check;
> >  		__be16 be16;
> >  		u8 bme680_cal_buf_1[BME680_CALIB_RANGE_1_LEN];
> 
> ...
> 
> > +static irqreturn_t bme680_trigger_handler(int irq, void *p)
> > +{
> > +	struct iio_poll_func *pf = p;
> > +	struct iio_dev *indio_dev = pf->indio_dev;
> > +	struct bme680_data *data = iio_priv(indio_dev);
> > +	u32 adc_temp, adc_press, adc_humid, comp_press, comp_humid;
> 
> > +	s32 *chans = (s32 *)data->buffer;
> 
> With the structure in place this becomes much more readable.
> 
> > +	u16 adc_gas_res, gas_regs_val;
> > +	s32 t_fine, comp_gas_res;
> > +	s16 comp_temp;
> > +	u8 gas_range;
> > +	int ret;
> > +
> > +	guard(mutex)(&data->lock);
> > +
> > +	ret = bme680_set_mode(data, BME680_FORCED);
> > +	if (ret < 0)
> > +		goto out;
> > +
> > +	ret = bme680_wait_for_eoc(data);
> > +	if (ret)
> > +		goto out;
> > +
> > +	/* Burst read data regs */
> > +	ret = regmap_bulk_read(data->regmap, BME680_REG_MEAS_STAT_0,
> > +			       data->buf, sizeof(data->buf));
> > +	if (ret) {
> > +		dev_err(data->dev, "failed to burst read sensor data\n");
> > +		goto out;
> > +	}
> > +	if (data->buf[0] & BME680_GAS_MEAS_BIT) {
> > +		dev_err(data->dev, "gas measurement incomplete\n");
> > +		goto out;
> > +	}
> > +
> > +	/* Temperature calculations */
> > +	adc_temp = FIELD_GET(BME680_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[5]));
> > +	if (adc_temp == BME680_MEAS_SKIPPED) {
> > +		dev_err(data->dev, "reading temperature skipped\n");
> > +		goto out;
> > +	}
> > +	comp_temp = bme680_compensate_temp(data, adc_temp);
> > +	t_fine = bme680_calc_t_fine(data, adc_temp);
> > +
> > +	/* Pressure calculations */
> > +	adc_press = FIELD_GET(BME680_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[2]));
> > +	if (adc_press == BME680_MEAS_SKIPPED) {
> > +		dev_err(data->dev, "reading pressure skipped\n");
> > +		goto out;
> > +	}
> > +	comp_press = bme680_compensate_press(data, adc_press, t_fine);
> 
> > +	pr_info("comp_press: %d\n", comp_press);
> 
> No debugging in the production code. Or if you really need that, it should
> use dev_dbg().
> 

ACK. I shouldn't have forgotten those here..

> > +	/* Humidity calculations */
> > +	adc_humid = get_unaligned_be16(&data->buf[8]);
> > +	if (adc_humid == BME680_MEAS_SKIPPED) {
> > +		dev_err(data->dev, "reading humidity skipped\n");
> > +		goto out;
> > +	}
> > +	comp_humid = bme680_compensate_humid(data, adc_humid, t_fine);
> 
> > +	pr_info("comp_humid: %d\n", comp_humid);
> 
> Ditto.
> 

ACK.

> > +
> > +	/* Gas calculations */
> > +	gas_regs_val = get_unaligned_be16(&data->buf[13]);
> > +	adc_gas_res = FIELD_GET(BME680_ADC_GAS_RES, gas_regs_val);
> > +	if ((gas_regs_val & BME680_GAS_STAB_BIT) == 0) {
> > +		dev_err(data->dev, "heater failed to reach the target temperature\n");
> > +		goto out;
> > +	}
> > +	gas_range = FIELD_GET(BME680_GAS_RANGE_MASK, gas_regs_val);
> > +	comp_gas_res = bme680_compensate_gas(data, adc_gas_res, gas_range);
> > +	pr_info("comp_gas_res: %d\n", comp_gas_res);
> > +
> > +	chans[0] = comp_temp;
> > +	chans[1] = comp_press;
> > +	chans[2] = comp_humid;
> > +	chans[3] = comp_gas_res;
> > +
> > +	/* Push to buffer */
> > +	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> > +					   iio_get_time_ns(indio_dev));
> > +out:
> > +	iio_trigger_notify_done(indio_dev->trig);
> > +	return IRQ_HANDLED;
> > +}
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

Cheers,
Vasilis

On Fri, 11 Oct 2024 21:07:20 +0200
Vasileios Aoiridis <vassilisamir@gmail.com> wrote:

> On Fri, Oct 11, 2024 at 01:37:56PM +0300, Andy Shevchenko wrote:
> > On Thu, Oct 10, 2024 at 11:00:29PM +0200, vamoirid wrote:  
> > > From: Vasileios Amoiridis <vassilisamir@gmail.com>
> > > 
> > > Add triggered buffer and soft timestamp support. The available scan mask
> > > enables all the channels of the sensor in order to follow the operation of
> > > the sensor. The sensor basically starts to capture from all channels
> > > as long as it enters into FORCED mode.  
> > 
> > ...
> >   
> > >  	struct regulator_bulk_data supplies[BME680_NUM_SUPPLIES];
> > >  	int ambient_temp;
> > >  
> > > +	u8 buffer[ALIGN(sizeof(s32) * BME680_NUM_CHANNELS, sizeof(s64))
> > > +		  + sizeof(s64)] __aligned(sizeof(s64));  
> > 
> > Can it be represented as a structure?
> > We also have aligned_s64 for the timestamp.
> >  
> 
> Hi Andy,
> 
> The same approach was used also for the bmp280 driver and since I was
> working on the bmp280 as well, I did it here. You think the
> representation as a struct would look better? Personally I like the
> nature of this one because of the ALIGN() but I have no problem of using
> a struct here.

Depends if you can enable sufficiently few channels that the timestamp
moves.  If that is the case, a structure is missleading as a representation
of this buffer so I prefer the above fun as it doesn't give the wrong
impression (by giving no impression at all of the data layout!)

Jonathan

On Sat, 12 Oct 2024 13:04:02 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 11 Oct 2024 21:07:20 +0200
> Vasileios Aoiridis <vassilisamir@gmail.com> wrote:
> 
> > On Fri, Oct 11, 2024 at 01:37:56PM +0300, Andy Shevchenko wrote:  
> > > On Thu, Oct 10, 2024 at 11:00:29PM +0200, vamoirid wrote:    
> > > > From: Vasileios Amoiridis <vassilisamir@gmail.com>
> > > > 
> > > > Add triggered buffer and soft timestamp support. The available scan mask
> > > > enables all the channels of the sensor in order to follow the operation of
> > > > the sensor. The sensor basically starts to capture from all channels
> > > > as long as it enters into FORCED mode.    
> > > 
> > > ...
> > >     
> > > >  	struct regulator_bulk_data supplies[BME680_NUM_SUPPLIES];
> > > >  	int ambient_temp;
> > > >  
> > > > +	u8 buffer[ALIGN(sizeof(s32) * BME680_NUM_CHANNELS, sizeof(s64))
> > > > +		  + sizeof(s64)] __aligned(sizeof(s64));    
> > > 
> > > Can it be represented as a structure?
> > > We also have aligned_s64 for the timestamp.
> > >    
> > 
> > Hi Andy,
> > 
> > The same approach was used also for the bmp280 driver and since I was
> > working on the bmp280 as well, I did it here. You think the
> > representation as a struct would look better? Personally I like the
> > nature of this one because of the ALIGN() but I have no problem of using
> > a struct here.  
> 
> Depends if you can enable sufficiently few channels that the timestamp
> moves.  If that is the case, a structure is missleading as a representation
> of this buffer so I prefer the above fun as it doesn't give the wrong
> impression (by giving no impression at all of the data layout!)
Looks like you always write them all to the buffer. So structure indeed
appropriate here. (I should have read the code before commenting!)

J
> 
> Jonathan