On Wed, 11 Aug 2021 18:18:02 -0300
Lucas Stankus [off-list ref] wrote:

ADXL313 is a small, thin, low power, 3-axis accelerometer with high
resolution measurement up to +/-4g. It includes an integrated 32-level
FIFO and has activity and inactivity sensing capabilities.

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL313.pdf
Signed-off-by: Lucas Stankus <lucas.p.stankus@gmail.com>
Reviewed-by: Alexandru Ardelean <redacted>

Hi Lucas,

I took another close look at this and I would like you to not use scan_index
as you are here.  It has a meaning tightly coupled to 'scans' which only exist
as a concept once you have buffered mode. The preferred way to get channel
specific values is to use addr and add a level of indirection (so a lookup
structure of some type).  A few more trivial things to add to what Andy raised
inline below.

Jonathan


...

I'm not in general keen on seeing scan_index being set in a driver that isn't providing
a buffer.  Whilst some of the scan_type can have valid meaning without buffering,
scan_index should not.

The use you are making of it here, should use addr.  So put a channel enum value
into addr and use that to look up both the _raw address to read and anything else
channel specific.  That will give more consistent code than you currently have
with a mixture of addr and scan_index being used depending on the particular
thing being read about the channel.

+	.scan_type = {							\
+		.sign = 's',						\
+		.realbits = 13,						\
+		.storagebits = 16,					\
+		.endianness = IIO_LE,					\

sign, storagebits and endianness are things that are only likely to matter once buffered
supported is added (where they relect the datalayout).  For now please drop setting
them at all.

+	},								\
+}
+
+static const struct iio_chan_spec adxl313_channels[] = {
+	ADXL313_ACCEL_CHANNEL(0, ADXL313_REG_DATAX, X),
+	ADXL313_ACCEL_CHANNEL(1, ADXL313_REG_DATAY, Y),
+	ADXL313_ACCEL_CHANNEL(2, ADXL313_REG_DATAZ, Z),
+};
+
+static int adxl313_set_odr(struct adxl313_data *data,
+			   unsigned int freq1, unsigned int freq2)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(adxl313_odr_freqs); i++) {
+		if (adxl313_odr_freqs[i][0] == freq1 &&
+		    adxl313_odr_freqs[i][1] == freq2)
+			break;
+	}
+
+	if (i == ARRAY_SIZE(adxl313_odr_freqs))
+		return -EINVAL;
+
+	return regmap_update_bits(data->regmap, ADXL313_REG_BW_RATE,
+				  ADXL313_RATE_MSK,
+				  FIELD_PREP(ADXL313_RATE_MSK,
+					     ADXL313_RATE_BASE + i));
+}
+
+static int adxl313_read_axis(struct adxl313_data *data,
+			     struct iio_chan_spec const *chan)
+{
+	int ret;
+
+	mutex_lock(&data->lock);
+
+	ret = regmap_bulk_read(data->regmap,
+			       chan->address,
+			       &data->transf_buf, 2);

sizeof(data->trasf_buf)

+	if (ret)
+		goto unlock_ret;
+
+	ret = le16_to_cpu(data->transf_buf);
+
+unlock_ret:
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
+static int adxl313_read_freq_avail(struct iio_dev *indio_dev,
+				   struct iio_chan_spec const *chan,
+				   const int **vals, int *type, int *length,
+				   long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*vals = (const int *)adxl313_odr_freqs;
+		*length = ARRAY_SIZE(adxl313_odr_freqs) * 2;
+		*type = IIO_VAL_INT_PLUS_MICRO;
+		return IIO_AVAIL_LIST;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int adxl313_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int *val, int *val2, long mask)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+	unsigned int regval;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = adxl313_read_axis(data, chan);
+		if (ret < 0)
+			return ret;
+
+		*val = sign_extend32(ret, chan->scan_type.realbits - 1);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		/*
+		 * Scale for any g range is given in datasheet as
+		 * 1024 LSB/g = 0.0009765625 * 9.80665 = 0.009576806640625 m/s^2
+		 */
+		*val = 0;
+		*val2 = 9576806;
+		return IIO_VAL_INT_PLUS_NANO;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		ret = regmap_read(data->regmap,
+				  ADXL313_REG_OFS_AXIS(chan->scan_index),

As mentioned above, don't use scan_index for this purpose.   There is no particular
reason the scan_index for a given channel won't be changed in future as part of some layout
optimization etc.  addr is for this purpose and often contains an enum value to that
gives a driver specific index of channels, then used to do things like you are doing here.

+				  &regval);
+		if (ret)
+			return ret;
+
+		/*
+		 * 8-bit resolution at +/- 0.5g, that is 4x accel data scale
+		 * factor at full resolution
+		 */
+		*val = sign_extend32(regval, 7) * 4;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		ret = regmap_read(data->regmap, ADXL313_REG_BW_RATE, &regval);
+		if (ret)
+			return ret;
+
+		ret = FIELD_GET(ADXL313_RATE_MSK, regval) - ADXL313_RATE_BASE;
+		*val = adxl313_odr_freqs[ret][0];
+		*val2 = adxl313_odr_freqs[ret][1];
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int adxl313_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	struct adxl313_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_CALIBBIAS:
+		/*
+		 * 8-bit resolution at +/- 0.5g, that is 4x accel data scale
+		 * factor at full resolution
+		 */
+		if (clamp_val(val, -128 * 4, 127 * 4) != val)
+			return -EINVAL;
+
+		return regmap_write(data->regmap,
+				    ADXL313_REG_OFS_AXIS(chan->scan_index),
+				    val / 4);
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		return adxl313_set_odr(data, val, val2);
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info adxl313_info = {
+	.read_raw	= adxl313_read_raw,
+	.write_raw	= adxl313_write_raw,
+	.read_avail	= adxl313_read_freq_avail
+};
+
+static int adxl313_setup(struct device *dev, struct adxl313_data *data,
+			 int (*interface_specific_setup)(struct device *,
+							 struct regmap *))
+{
+	unsigned int regval;
+	int ret;
+
+	/* Ensures the device is in a consistent state after start up */
+	ret = regmap_write(data->regmap, ADXL313_REG_SOFT_RESET,
+			   ADXL313_SOFT_RESET);
+	if (ret)
+		return ret;
+
+	if (interface_specific_setup) {
+		ret = interface_specific_setup(dev, data->regmap);
+		if (ret)
+			return ret;
+	}
+
+	ret = regmap_read(data->regmap, ADXL313_REG_DEVID0, &regval);
+	if (ret)
+		return ret;
+
+	if (regval != ADXL313_DEVID0) {
+		dev_err(dev, "Invalid manufacturer ID: 0x%02x\n", regval);
+		return -ENODEV;
+	}
+
+	ret = regmap_read(data->regmap, ADXL313_REG_DEVID1, &regval);
+	if (ret)
+		return ret;
+
+	if (regval != ADXL313_DEVID1) {
+		dev_err(dev, "Invalid mems ID: 0x%02x\n", regval);
+		return -ENODEV;
+	}
+
+	ret = regmap_read(data->regmap, ADXL313_REG_PARTID, &regval);
+	if (ret)
+		return ret;
+
+	if (regval != ADXL313_PARTID) {
+		dev_err(dev, "Invalid device ID: 0x%02x\n", regval);
+		return -ENODEV;
+	}
+
+	/* Sets the range to +/- 4g */
+	ret = regmap_update_bits(data->regmap, ADXL313_REG_DATA_FORMAT,
+				 ADXL313_RANGE_MSK,
+				 FIELD_PREP(ADXL313_RANGE_MSK,
+					    ADXL313_RANGE_4G));
+	if (ret)
+		return ret;
+
+	/* Enables full resolution */
+	ret = regmap_update_bits(data->regmap, ADXL313_REG_DATA_FORMAT,
+				 ADXL313_FULL_RES, ADXL313_FULL_RES);
+	if (ret)
+		return ret;
+
+	/* Enables measurement mode */
+	return regmap_update_bits(data->regmap, ADXL313_REG_POWER_CTL,
+				  ADXL313_POWER_CTL_MSK,
+				  ADXL313_MEASUREMENT_MODE);
+}
+
+int adxl313_core_probe(struct device *dev,
+		       struct regmap *regmap,
+		       const char *name,
+		       int (*interface_specific_setup)(struct device *,
+						       struct regmap *))
+{
+	struct adxl313_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->regmap = regmap;
+	mutex_init(&data->lock);
+
+	indio_dev->name = name;
+	indio_dev->info = &adxl313_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = adxl313_channels;
+	indio_dev->num_channels = ARRAY_SIZE(adxl313_channels);
+
+	ret = adxl313_setup(dev, data, interface_specific_setup);
+	if (ret) {
+		dev_err(dev, "ADXL313 setup failed\n");
+		return ret;
+	}
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+EXPORT_SYMBOL_GPL(adxl313_core_probe);
+
+MODULE_AUTHOR("Lucas Stankus [off-list ref]");
+MODULE_DESCRIPTION("ADXL313 3-Axis Digital Accelerometer core driver");
+MODULE_LICENSE("GPL v2");

Seeing as you are going to be doing a v4, please add explicit includes
 for mod_devicetable.h which contains the of_device_id struct definition.
Same for the i2c driver.

+
+#include "adxl313.h"
+

...