Add a new functionality to ad7779 driver that streams data through data
output interface using IIO backend interface.

Signed-off-by: Ioana Risteiu <Ioana.Risteiu@analog.com>
---
changes in v5:
 - fix indentation 
 - change num_lanes variable from int to u32 type
 - use unsigned int in for loop declaration
 drivers/iio/adc/ad7779.c | 115 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 114 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7779.c b/drivers/iio/adc/ad7779.c
index b4e56983201c..3776af1c65e9 100644
--- a/drivers/iio/adc/ad7779.c
+++ b/drivers/iio/adc/ad7779.c
@@ -25,6 +25,7 @@
 #include <linux/units.h>
 
 #include <linux/iio/iio.h>
+#include <linux/iio/backend.h>
 #include <linux/iio/buffer.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/trigger.h>
@@ -116,6 +117,12 @@
 #define AD7779_CRC8_POLY			0x07
 DECLARE_CRC8_TABLE(ad7779_crc8_table);
 
+enum ad7779_data_lines {
+	AD7779_1LINE = 1,
+	AD7779_2LINES = 2,
+	AD7779_4LINES = 4,
+};
+
 enum ad7779_filter {
 	AD7779_SINC3,
 	AD7779_SINC5,
@@ -145,6 +152,7 @@ struct ad7779_state {
 	struct completion completion;
 	unsigned int sampling_freq;
 	enum ad7779_filter filter_enabled;
+	struct iio_backend *back;
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
@@ -630,12 +638,38 @@ static int ad7779_reset(struct iio_dev *indio_dev, struct gpio_desc *reset_gpio)
 	return ret;
 }
 
+static int ad7779_update_scan_mode(struct iio_dev *indio_dev,
+				   const unsigned long *scan_mask)
+{
+	struct ad7779_state *st = iio_priv(indio_dev);
+	unsigned int c;
+	int ret;
+
+	for (c = 0; c < AD7779_NUM_CHANNELS; c++) {
+		if (test_bit(c, scan_mask))
+			ret = iio_backend_chan_enable(st->back, c);
+		else
+			ret = iio_backend_chan_disable(st->back, c);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static const struct iio_info ad7779_info = {
 	.read_raw = ad7779_read_raw,
 	.write_raw = ad7779_write_raw,
 	.debugfs_reg_access = &ad7779_reg_access,
 };
 
+static const struct iio_info ad7779_info_data = {
+	.read_raw = ad7779_read_raw,
+	.write_raw = ad7779_write_raw,
+	.debugfs_reg_access = &ad7779_reg_access,
+	.update_scan_mode = &ad7779_update_scan_mode,
+};
+
 static const struct iio_enum ad7779_filter_enum = {
 	.items = ad7779_filter_type,
 	.num_items = ARRAY_SIZE(ad7779_filter_type),
@@ -752,6 +786,48 @@ static int ad7779_conf(struct ad7779_state *st, struct gpio_desc *start_gpio)
 	return 0;
 }
 
+static int ad7779_set_data_lines(struct iio_dev *indio_dev, u32 num_lanes)
+{
+	struct ad7779_state *st = iio_priv(indio_dev);
+	int ret;
+
+	if (num_lanes != AD7779_1LINE &&
+		num_lanes != AD7779_2LINES &&
+		num_lanes != AD7779_4LINES)
+		return -EINVAL;
+
+	ret = ad7779_set_sampling_frequency(st, num_lanes * AD7779_DEFAULT_SAMPLING_1LINE);
+	if (ret)
+		return ret;
+
+	ret = iio_backend_num_lanes_set(st->back, num_lanes);
+	if (ret)
+		return ret;
+
+	return ad7779_spi_write_mask(st, AD7779_REG_DOUT_FORMAT,
+				     AD7779_DOUT_FORMAT_MSK,
+				     FIELD_PREP(AD7779_DOUT_FORMAT_MSK, 2 - ilog2(num_lanes)));
+}
+
+static int ad7779_setup_channels(struct iio_dev *indio_dev, const struct ad7779_state *st)
+{
+	struct iio_chan_spec *channels;
+	struct device *dev = &st->spi->dev;
+
+	channels = devm_kmemdup_array(dev, st->chip_info->channels,
+				      ARRAY_SIZE(ad7779_channels),
+				      sizeof(*channels), GFP_KERNEL);
+	if (!channels)
+		return -ENOMEM;
+
+	for (unsigned int i = 0; i < ARRAY_SIZE(ad7779_channels); i++)
+		channels[i].scan_type.endianness = IIO_CPU;
+
+	indio_dev->channels = channels;
+
+	return 0;
+}
+
 static int ad7779_setup_without_backend(struct ad7779_state *st, struct iio_dev *indio_dev)
 {
 	int ret;
@@ -796,6 +872,39 @@ static int ad7779_setup_without_backend(struct ad7779_state *st, struct iio_dev
 				     FIELD_PREP(AD7779_DCLK_CLK_DIV_MSK, 7));
 }
 
+static int ad7779_setup_backend(struct ad7779_state *st, struct iio_dev *indio_dev)
+{
+	struct device *dev = &st->spi->dev;
+	int ret;
+	u32 num_lanes;
+
+	indio_dev->info = &ad7779_info_data;
+
+	ret = ad7779_setup_channels(indio_dev, st);
+	if (ret)
+		return ret;
+
+	st->back = devm_iio_backend_get(dev, NULL);
+	if (IS_ERR(st->back))
+		return dev_err_probe(dev, PTR_ERR(st->back),
+				     "failed to get iio backend");
+
+	ret = devm_iio_backend_request_buffer(dev, st->back, indio_dev);
+	if (ret)
+		return ret;
+
+	ret = devm_iio_backend_enable(dev, st->back);
+	if (ret)
+		return ret;
+
+	num_lanes = 4;
+	ret = device_property_read_u32(dev, "adi,num-lanes", &num_lanes);
+	if (ret && ret != -EINVAL)
+		return ret;
+
+	return ad7779_set_data_lines(indio_dev, num_lanes);
+}
+
 static int ad7779_probe(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev;
@@ -848,7 +957,10 @@ static int ad7779_probe(struct spi_device *spi)
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->num_channels = ARRAY_SIZE(ad7779_channels);
 
-	ret = ad7779_setup_without_backend(st, indio_dev);
+	if (device_property_present(dev, "io-backends"))
+		ret = ad7779_setup_backend(st, indio_dev);
+	else
+		ret = ad7779_setup_without_backend(st, indio_dev);
 	if (ret)
 		return ret;
 
@@ -942,3 +1054,4 @@ module_spi_driver(ad7779_driver);
 MODULE_AUTHOR("Ramona Alexandra Nechita <ramona.nechita@analog.com>");
 MODULE_DESCRIPTION("Analog Devices AD7779 ADC");
 MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_BACKEND");
-- 
2.47.2

On Mon, 25 Aug 2025 13:51:19 +0300
Ioana Risteiu <Ioana.Risteiu@analog.com> wrote:

> Add a new functionality to ad7779 driver that streams data through data
> output interface using IIO backend interface.
> 
> Signed-off-by: Ioana Risteiu <Ioana.Risteiu@analog.com>
> ---
> changes in v5:
>  - fix indentation 
>  - change num_lanes variable from int to u32 type
>  - use unsigned int in for loop declaration
>  drivers/iio/adc/ad7779.c | 115 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 114 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ad7779.c b/drivers/iio/adc/ad7779.c
> index b4e56983201c..3776af1c65e9 100644
> --- a/drivers/iio/adc/ad7779.c
> +++ b/drivers/iio/adc/ad7779.c
> @@ -25,6 +25,7 @@
>  #include <linux/units.h>
>  
>  #include <linux/iio/iio.h>
> +#include <linux/iio/backend.h>
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/sysfs.h>
>  #include <linux/iio/trigger.h>
> @@ -116,6 +117,12 @@
>  #define AD7779_CRC8_POLY			0x07
>  DECLARE_CRC8_TABLE(ad7779_crc8_table);
>  
> +enum ad7779_data_lines {
> +	AD7779_1LINE = 1,
> +	AD7779_2LINES = 2,
> +	AD7779_4LINES = 4,

Probably crossed with the review I did earlier.
This enum doesn't add anything that I can see over just using the value inline.
If anything it hurts readability.

> +};

> +static int ad7779_set_data_lines(struct iio_dev *indio_dev, u32 num_lanes)
> +{
> +	struct ad7779_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (num_lanes != AD7779_1LINE &&
> +		num_lanes != AD7779_2LINES &&
> +		num_lanes != AD7779_4LINES)
> +		return -EINVAL;
	if (num_lanes != 4 && num_lanes != 2 && num_lanes != 1)
is much clearer to my eyes without the macros.

On Mon, Aug 25, 2025 at 01:51:19PM +0300, Ioana Risteiu wrote:
> Add a new functionality to ad7779 driver that streams data through data
> output interface using IIO backend interface.

...

> +static int ad7779_set_data_lines(struct iio_dev *indio_dev, u32 num_lanes)
> +{
> +	struct ad7779_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (num_lanes != AD7779_1LINE &&
> +		num_lanes != AD7779_2LINES &&
> +		num_lanes != AD7779_4LINES)

Wrong indentation.

> +		return -EINVAL;
> +
> +	ret = ad7779_set_sampling_frequency(st, num_lanes * AD7779_DEFAULT_SAMPLING_1LINE);
> +	if (ret)
> +		return ret;
> +
> +	ret = iio_backend_num_lanes_set(st->back, num_lanes);
> +	if (ret)
> +		return ret;
> +
> +	return ad7779_spi_write_mask(st, AD7779_REG_DOUT_FORMAT,
> +				     AD7779_DOUT_FORMAT_MSK,
> +				     FIELD_PREP(AD7779_DOUT_FORMAT_MSK, 2 - ilog2(num_lanes)));
> +}

...

> +static int ad7779_setup_channels(struct iio_dev *indio_dev, const struct ad7779_state *st)
> +{
> +	struct iio_chan_spec *channels;
> +	struct device *dev = &st->spi->dev;
> +
> +	channels = devm_kmemdup_array(dev, st->chip_info->channels,
> +				      ARRAY_SIZE(ad7779_channels),
> +				      sizeof(*channels), GFP_KERNEL);
> +	if (!channels)
> +		return -ENOMEM;
> +
> +	for (unsigned int i = 0; i < ARRAY_SIZE(ad7779_channels); i++)
> +		channels[i].scan_type.endianness = IIO_CPU;
> +
> +	indio_dev->channels = channels;

So, here I expect to see num_channels assignment as well as near to any other
channels assignment.

> +
> +	return 0;
> +}

Otherwise LGTM.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

-- 
With Best Regards,
Andy Shevchenko