drivers/iio/adc/ltc2471.c

Source file repositories/reference/linux-study-clean/drivers/iio/adc/ltc2471.c

File Facts

System
Linux kernel
Corpus path
drivers/iio/adc/ltc2471.c
Extension
.c
Size
3623 bytes
Lines
158
Domain
Driver Families
Bucket
drivers/iio
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct ltc2471_data {
	struct i2c_client *client;
};

/* Reference voltage is 1.25V */
#define LTC2471_VREF 1250

/* Read two bytes from the I2C bus to obtain the ADC result */
static int ltc2471_get_value(struct i2c_client *client)
{
	int ret;
	__be16 buf;

	ret = i2c_master_recv(client, (char *)&buf, sizeof(buf));
	if (ret < 0)
		return ret;
	if (ret != sizeof(buf))
		return -EIO;

	/* MSB first */
	return be16_to_cpu(buf);
}

static int ltc2471_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan,
			    int *val, int *val2, long info)
{
	struct ltc2471_data *data = iio_priv(indio_dev);
	int ret;

	switch (info) {
	case IIO_CHAN_INFO_RAW:
		ret = ltc2471_get_value(data->client);
		if (ret < 0)
			return ret;
		*val = ret;
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
		if (chan->differential)
			/* Output ranges from -VREF to +VREF */
			*val = 2 * LTC2471_VREF;
		else
			/* Output ranges from 0 to VREF */
			*val = LTC2471_VREF;
		*val2 = 16;	/* 16 data bits */
		return IIO_VAL_FRACTIONAL_LOG2;

	case IIO_CHAN_INFO_OFFSET:
		/* Only differential chip has this property */
		*val = -LTC2471_VREF;
		return IIO_VAL_INT;

	default:
		return -EINVAL;
	}
}

static const struct iio_chan_spec ltc2471_channel[] = {
	{
		.type = IIO_VOLTAGE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
	},
};

static const struct iio_chan_spec ltc2473_channel[] = {
	{
		.type = IIO_VOLTAGE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
					    BIT(IIO_CHAN_INFO_OFFSET),
		.differential = 1,
	},
};

static const struct iio_info ltc2471_info = {
	.read_raw = ltc2471_read_raw,
};

static int ltc2471_i2c_probe(struct i2c_client *client)
{
	const struct i2c_device_id *id = i2c_client_get_device_id(client);
	struct iio_dev *indio_dev;
	struct ltc2471_data *data;
	int ret;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -EOPNOTSUPP;

Annotation

Implementation Notes