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>
---
 drivers/iio/adc/ad7779.c | 242 +++++++++++++++++++++++++++++----------
 1 file changed, 183 insertions(+), 59 deletions(-)

diff --git a/drivers/iio/adc/ad7779.c b/drivers/iio/adc/ad7779.c
index 845adc510239..a69fda1f4581 100644
--- a/drivers/iio/adc/ad7779.c
+++ b/drivers/iio/adc/ad7779.c
@@ -31,6 +31,8 @@
 #include <linux/iio/triggered_buffer.h>
 #include <linux/iio/trigger_consumer.h>
 
+#include <linux/iio/backend.h>
+
 #define AD7779_SPI_READ_CMD			BIT(7)
 
 #define AD7779_DISABLE_SD			BIT(7)
@@ -116,6 +118,12 @@
 #define AD7779_CRC8_POLY			0x07
 DECLARE_CRC8_TABLE(ad7779_crc8_table);
 
+enum ad7779_data_lines {
+	AD7779_4LINES = 4,
+	AD7779_2LINES = 2,
+	AD7779_1LINE = 1,
+};
+
 enum ad7779_filter {
 	AD7779_SINC3,
 	AD7779_SINC5,
@@ -157,6 +165,8 @@ struct ad7779_state {
 	u8			reg_rx_buf[3];
 	u8			reg_tx_buf[3];
 	u8			reset_buf[8];
+
+	struct iio_backend *back;
 };
 
 static const char * const ad7779_filter_type[] = {
@@ -630,12 +640,38 @@ 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),
@@ -650,7 +686,7 @@ static const struct iio_chan_spec_ext_info ad7779_ext_filter[] = {
 	{ }
 };
 
-#define AD777x_CHAN_S(index, _ext_info)					\
+#define AD777X_CHAN_S(index, _ext_info)					\
 	{								\
 		.type = IIO_VOLTAGE,					\
 		.info_mask_separate = BIT(IIO_CHAN_INFO_CALIBSCALE)  |	\
@@ -669,32 +705,33 @@ static const struct iio_chan_spec_ext_info ad7779_ext_filter[] = {
 		},							\
 	}
 
-#define AD777x_CHAN_NO_FILTER_S(index)					\
-	AD777x_CHAN_S(index, NULL)
+#define AD777X_CHAN_NO_FILTER_S(index)					\
+	AD777X_CHAN_S(index, NULL)
+
+#define AD777X_CHAN_FILTER_S(index)					\
+	AD777X_CHAN_S(index, ad7779_ext_filter)
 
-#define AD777x_CHAN_FILTER_S(index)					\
-	AD777x_CHAN_S(index, ad7779_ext_filter)
 static const struct iio_chan_spec ad7779_channels[] = {
-	AD777x_CHAN_NO_FILTER_S(0),
-	AD777x_CHAN_NO_FILTER_S(1),
-	AD777x_CHAN_NO_FILTER_S(2),
-	AD777x_CHAN_NO_FILTER_S(3),
-	AD777x_CHAN_NO_FILTER_S(4),
-	AD777x_CHAN_NO_FILTER_S(5),
-	AD777x_CHAN_NO_FILTER_S(6),
-	AD777x_CHAN_NO_FILTER_S(7),
+	AD777X_CHAN_NO_FILTER_S(0),
+	AD777X_CHAN_NO_FILTER_S(1),
+	AD777X_CHAN_NO_FILTER_S(2),
+	AD777X_CHAN_NO_FILTER_S(3),
+	AD777X_CHAN_NO_FILTER_S(4),
+	AD777X_CHAN_NO_FILTER_S(5),
+	AD777X_CHAN_NO_FILTER_S(6),
+	AD777X_CHAN_NO_FILTER_S(7),
 	IIO_CHAN_SOFT_TIMESTAMP(8),
 };
 
 static const struct iio_chan_spec ad7779_channels_filter[] = {
-	AD777x_CHAN_FILTER_S(0),
-	AD777x_CHAN_FILTER_S(1),
-	AD777x_CHAN_FILTER_S(2),
-	AD777x_CHAN_FILTER_S(3),
-	AD777x_CHAN_FILTER_S(4),
-	AD777x_CHAN_FILTER_S(5),
-	AD777x_CHAN_FILTER_S(6),
-	AD777x_CHAN_FILTER_S(7),
+	AD777X_CHAN_FILTER_S(0),
+	AD777X_CHAN_FILTER_S(1),
+	AD777X_CHAN_FILTER_S(2),
+	AD777X_CHAN_FILTER_S(3),
+	AD777X_CHAN_FILTER_S(4),
+	AD777X_CHAN_FILTER_S(5),
+	AD777X_CHAN_FILTER_S(6),
+	AD777X_CHAN_FILTER_S(7),
 	IIO_CHAN_SOFT_TIMESTAMP(8),
 };
 
@@ -752,6 +789,126 @@ 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,
+				 unsigned int num_lanes)
+{
+	struct ad7779_state *st = iio_priv(indio_dev);
+	int ret;
+
+	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_conf_channels(struct iio_dev *indio_dev, const struct ad7779_state *st)
+{
+	struct iio_chan_spec *channels;
+	struct device *dev = &st->spi->dev;
+	int num_channels = ARRAY_SIZE(ad7779_channels);
+
+	channels = devm_kcalloc(dev, num_channels, sizeof(*channels), GFP_KERNEL);
+	if (!channels)
+		return -ENOMEM;
+
+	memcpy(channels, st->chip_info->channels, num_channels * sizeof(struct iio_chan_spec));
+
+	for (int i = 0; i < 8; i++)
+		channels[i].scan_type.endianness = IIO_CPU;
+
+	indio_dev->channels = channels;
+
+	return 0;
+}
+
+static int setup_irq(struct ad7779_state *st, struct iio_dev *indio_dev)
+{
+	int ret;
+	struct device *dev = &st->spi->dev;
+
+	indio_dev->info = &ad7779_info;
+	indio_dev->channels = st->chip_info->channels;
+
+	st->trig = devm_iio_trigger_alloc(dev, "%s-dev%d", indio_dev->name,
+					  iio_device_id(indio_dev));
+	if (!st->trig)
+		return -ENOMEM;
+
+	st->trig->ops = &ad7779_trigger_ops;
+
+	iio_trigger_set_drvdata(st->trig, st);
+
+	ret = devm_request_irq(dev, st->spi->irq, iio_trigger_generic_data_rdy_poll,
+			       IRQF_ONESHOT | IRQF_NO_AUTOEN, indio_dev->name,
+			       st->trig);
+	if (ret)
+		return dev_err_probe(dev, ret, "request IRQ %d failed\n",
+					st->spi->irq);
+
+	ret = devm_iio_trigger_register(dev, st->trig);
+	if (ret)
+		return ret;
+
+	indio_dev->trig = iio_trigger_get(st->trig);
+
+	init_completion(&st->completion);
+
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
+					      &iio_pollfunc_store_time,
+					      &ad7779_trigger_handler,
+					      &ad7779_buffer_setup_ops);
+	if (ret)
+		return ret;
+
+	ret = ad7779_spi_write_mask(st, AD7779_REG_DOUT_FORMAT,
+				    AD7779_DCLK_CLK_DIV_MSK,
+				    FIELD_PREP(AD7779_DCLK_CLK_DIV_MSK, 7));
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int setup_back(struct ad7779_state *st, struct iio_dev *indio_dev)
+{
+	struct device *dev = &st->spi->dev;
+	int ret = -EINVAL;
+	int num_lanes;
+
+	indio_dev->info = &ad7779_info_data;
+
+	ret = ad7779_conf_channels(indio_dev, st);
+	if (ret)
+		return ret;
+
+	st->back = devm_iio_backend_get(dev, NULL);
+	if (IS_ERR(st->back)) {
+		dev_err_probe(dev, ret, "failed to get iio backend");
+		return PTR_ERR(st->back);
+	}
+
+	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;
+
+	ret = device_property_read_u32(dev, "adi,num-lanes", &num_lanes);
+	if (ret < 0)
+		return ad7779_set_data_lines(indio_dev, 4);
+
+	return ad7779_set_data_lines(indio_dev, num_lanes);
+}
+
 static int ad7779_probe(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev;
@@ -760,9 +917,6 @@ static int ad7779_probe(struct spi_device *spi)
 	struct device *dev = &spi->dev;
 	int ret = -EINVAL;
 
-	if (!spi->irq)
-		return dev_err_probe(dev, ret, "DRDY irq not present\n");
-
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
 	if (!indio_dev)
 		return -ENOMEM;
@@ -804,45 +958,14 @@ static int ad7779_probe(struct spi_device *spi)
 		return ret;
 
 	indio_dev->name = st->chip_info->name;
-	indio_dev->info = &ad7779_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
-	indio_dev->channels = st->chip_info->channels;
 	indio_dev->num_channels = ARRAY_SIZE(ad7779_channels);
 
-	st->trig = devm_iio_trigger_alloc(dev, "%s-dev%d", indio_dev->name,
-					  iio_device_id(indio_dev));
-	if (!st->trig)
-		return -ENOMEM;
-
-	st->trig->ops = &ad7779_trigger_ops;
-
-	iio_trigger_set_drvdata(st->trig, st);
-
-	ret = devm_request_irq(dev, spi->irq, iio_trigger_generic_data_rdy_poll,
-			       IRQF_ONESHOT | IRQF_NO_AUTOEN, indio_dev->name,
-			       st->trig);
-	if (ret)
-		return dev_err_probe(dev, ret, "request IRQ %d failed\n",
-				     st->spi->irq);
-
-	ret = devm_iio_trigger_register(dev, st->trig);
-	if (ret)
-		return ret;
-
-	indio_dev->trig = iio_trigger_get(st->trig);
-
-	init_completion(&st->completion);
-
-	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
-					      &iio_pollfunc_store_time,
-					      &ad7779_trigger_handler,
-					      &ad7779_buffer_setup_ops);
-	if (ret)
-		return ret;
+	if (device_property_present(dev, "io-backends"))
+		ret = setup_back(st, indio_dev);
+	else
+		ret = setup_irq(st, indio_dev);
 
-	ret = ad7779_spi_write_mask(st, AD7779_REG_DOUT_FORMAT,
-				    AD7779_DCLK_CLK_DIV_MSK,
-				    FIELD_PREP(AD7779_DCLK_CLK_DIV_MSK, 7));
 	if (ret)
 		return ret;
 
@@ -936,3 +1059,4 @@ 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

Hi Ioana,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ioana-Risteiu/iio-adc-adi-axi-adc-add-axi_adc_num_lanes_set/20250807-032923
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
patch link:    https://lore.kernel.org/r/20250806192502.10120-4-Ioana.Risteiu%40analog.com
patch subject: [PATCH v2 3/3] iio: adc: update ad7779 to use IIO backend
config: x86_64-randconfig-161-20250809 (https://download.01.org/0day-ci/archive/20250809/202508090909.tqDX7ah1-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202508090909.tqDX7ah1-lkp@intel.com/

smatch warnings:
drivers/iio/adc/ad7779.c:893 setup_back() warn: passing zero to 'dev_err_probe'

vim +/dev_err_probe +893 drivers/iio/adc/ad7779.c

1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  879  static int setup_back(struct ad7779_state *st, struct iio_dev *indio_dev)
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  880  {
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  881  	struct device *dev = &st->spi->dev;
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  882  	int ret = -EINVAL;
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  883  	int num_lanes;
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  884  
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  885  	indio_dev->info = &ad7779_info_data;
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  886  
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  887  	ret = ad7779_conf_channels(indio_dev, st);
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  888  	if (ret)
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  889  		return ret;
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  890  
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  891  	st->back = devm_iio_backend_get(dev, NULL);
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  892  	if (IS_ERR(st->back)) {
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06 @893  		dev_err_probe(dev, ret, "failed to get iio backend");

s/ret/PTR_ERR(st->back)/

1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  894  		return PTR_ERR(st->back);

Change this to:

	if (IS_ERR(st->back))
		return dev_err_probe(dev, PTR_ERR(st->back),
				     "failed to get iio backend");

1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  895  	}
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  896  
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  897  	ret = devm_iio_backend_request_buffer(dev, st->back, indio_dev);
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  898  	if (ret)
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  899  		return ret;
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  900  
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  901  	ret = devm_iio_backend_enable(dev, st->back);
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  902  	if (ret)
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  903  		return ret;
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  904  
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  905  	ret = device_property_read_u32(dev, "adi,num-lanes", &num_lanes);
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  906  	if (ret < 0)
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  907  		return ad7779_set_data_lines(indio_dev, 4);
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  908  
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  909  	return ad7779_set_data_lines(indio_dev, num_lanes);
1d61d2e4f96ac5 Ioana Risteiu 2025-08-06  910  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

On Wed, 6 Aug 2025 22:25:00 +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>
Hi Ionna,

>  
> +static int ad7779_set_data_lines(struct iio_dev *indio_dev,
> +				 unsigned int num_lanes)
> +{
> +	struct ad7779_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	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_conf_channels(struct iio_dev *indio_dev, const struct ad7779_state *st)

As per other branch of thread.  This needs a name that makes it more
obvious it's a probe time setup rather that anything to do with configuring
channels at runtime.

> +{
> +	struct iio_chan_spec *channels;
> +	struct device *dev = &st->spi->dev;
> +	int num_channels = ARRAY_SIZE(ad7779_channels);
> +
> +	channels = devm_kcalloc(dev, num_channels, sizeof(*channels), GFP_KERNEL);
devm_kmemdup_array()?

> +	if (!channels)
> +		return -ENOMEM;
> +
> +	memcpy(channels, st->chip_info->channels, num_channels * sizeof(struct iio_chan_spec));
> +
> +	for (int i = 0; i < 8; i++)

Andy got this, but make sure to get that 8 from somewhere. It's num_channels I think. 
Though given most of this code collapses into a single call to devm_kmemdup_array()
I think that local variable may not make much sense. ARRAY_SIZE may be clearer.

> +		channels[i].scan_type.endianness = IIO_CPU;
> +
> +	indio_dev->channels = channels;
> +
> +	return 0;
> +}
> +
> +static int setup_irq(struct ad7779_state *st, struct iio_dev *indio_dev)

As below. Do this in a precursor patch and give it a better name!
Pretty much everything in IIO driver gets namespaced with a driver
specific prefix. Makes future problems with new generic functions
much less likely and makes it clear what is local to the driver.

> +{
> +	int ret;
> +	struct device *dev = &st->spi->dev;
> +
> +	indio_dev->info = &ad7779_info;
> +	indio_dev->channels = st->chip_info->channels;
> +
> +	st->trig = devm_iio_trigger_alloc(dev, "%s-dev%d", indio_dev->name,
> +					  iio_device_id(indio_dev));
> +	if (!st->trig)
> +		return -ENOMEM;
> +
> +	st->trig->ops = &ad7779_trigger_ops;
> +
> +	iio_trigger_set_drvdata(st->trig, st);
> +
> +	ret = devm_request_irq(dev, st->spi->irq, iio_trigger_generic_data_rdy_poll,
> +			       IRQF_ONESHOT | IRQF_NO_AUTOEN, indio_dev->name,
> +			       st->trig);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "request IRQ %d failed\n",
> +					st->spi->irq);
> +
> +	ret = devm_iio_trigger_register(dev, st->trig);
> +	if (ret)
> +		return ret;
> +
> +	indio_dev->trig = iio_trigger_get(st->trig);
> +
> +	init_completion(&st->completion);
> +
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
> +					      &iio_pollfunc_store_time,
> +					      &ad7779_trigger_handler,
> +					      &ad7779_buffer_setup_ops);
> +	if (ret)
> +		return ret;
> +
> +	ret = ad7779_spi_write_mask(st, AD7779_REG_DOUT_FORMAT,
> +				    AD7779_DCLK_CLK_DIV_MSK,
> +				    FIELD_PREP(AD7779_DCLK_CLK_DIV_MSK, 7));

return ad7779_spi_write_mask...

> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +static int setup_back(struct ad7779_state *st, struct iio_dev *indio_dev)
> +{
> +	struct device *dev = &st->spi->dev;
> +	int ret = -EINVAL;
> +	int num_lanes;
> +
> +	indio_dev->info = &ad7779_info_data;
> +
> +	ret = ad7779_conf_channels(indio_dev, st);
> +	if (ret)
> +		return ret;
> +
> +	st->back = devm_iio_backend_get(dev, NULL);
> +	if (IS_ERR(st->back)) {
> +		dev_err_probe(dev, ret, "failed to get iio backend");
ret == 0 which isn't what you want.
> +		return PTR_ERR(st->back);

I think Andy pointed this out as well.  I'm not being too careful to not
duplicate unless I happen to remember he covered something in the earlier
review.

> +	}
> +
> +	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;
> +
> +	ret = device_property_read_u32(dev, "adi,num-lanes", &num_lanes);
> +	if (ret < 0)

Whilst it's a bit fiddly as this is an array read underneath, the fact
num_lanes is not null is enough to ensure if (ret) is fine here.

> +		return ad7779_set_data_lines(indio_dev, 4);
> +
> +	return ad7779_set_data_lines(indio_dev, num_lanes);
> +}
> +
>  static int ad7779_probe(struct spi_device *spi)
>  {
>  	struct iio_dev *indio_dev;
> @@ -760,9 +917,6 @@ static int ad7779_probe(struct spi_device *spi)
>  	struct device *dev = &spi->dev;
>  	int ret = -EINVAL;
>  
> -	if (!spi->irq)
> -		return dev_err_probe(dev, ret, "DRDY irq not present\n");
> -
>  	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
>  	if (!indio_dev)
>  		return -ENOMEM;
> @@ -804,45 +958,14 @@ static int ad7779_probe(struct spi_device *spi)
>  		return ret;
>  
>  	indio_dev->name = st->chip_info->name;
> -	indio_dev->info = &ad7779_info;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
> -	indio_dev->channels = st->chip_info->channels;
>  	indio_dev->num_channels = ARRAY_SIZE(ad7779_channels);
>  
> -	st->trig = devm_iio_trigger_alloc(dev, "%s-dev%d", indio_dev->name,
> -					  iio_device_id(indio_dev));
> -	if (!st->trig)
> -		return -ENOMEM;
> -
> -	st->trig->ops = &ad7779_trigger_ops;
> -
> -	iio_trigger_set_drvdata(st->trig, st);
> -
> -	ret = devm_request_irq(dev, spi->irq, iio_trigger_generic_data_rdy_poll,
> -			       IRQF_ONESHOT | IRQF_NO_AUTOEN, indio_dev->name,
> -			       st->trig);
> -	if (ret)
> -		return dev_err_probe(dev, ret, "request IRQ %d failed\n",
> -				     st->spi->irq);
> -
> -	ret = devm_iio_trigger_register(dev, st->trig);
> -	if (ret)
> -		return ret;
> -
> -	indio_dev->trig = iio_trigger_get(st->trig);
> -
> -	init_completion(&st->completion);
> -
> -	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
> -					      &iio_pollfunc_store_time,
> -					      &ad7779_trigger_handler,
> -					      &ad7779_buffer_setup_ops);
> -	if (ret)
> -		return ret;
> +	if (device_property_present(dev, "io-backends"))
> +		ret = setup_back(st, indio_dev);
> +	else
> +		ret = setup_irq(st, indio_dev);

Do the factoring out of the setup_irq stuff in a precursor patch.
Then this one will just make it conditional as part of adding the new backend stuff.

setup_irq isn't a good name. It does a bunch of things that aren't
directly related to the irq.  Prefix the function as well
ad7779_setup_without_backend() maybe?


>  
> -	ret = ad7779_spi_write_mask(st, AD7779_REG_DOUT_FORMAT,
> -				    AD7779_DCLK_CLK_DIV_MSK,
> -				    FIELD_PREP(AD7779_DCLK_CLK_DIV_MSK, 7));
>  	if (ret)
>  		return ret;
>  
> @@ -936,3 +1059,4 @@ 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");

On Wed, Aug 06, 2025 at 10:25:00PM +0300, Ioana Risteiu wrote:
> Add a new functionality to ad7779 driver that streams data through data
> output interface using IIO backend interface.

...

> +enum ad7779_data_lines {
> +	AD7779_4LINES = 4,
> +	AD7779_2LINES = 2,
> +	AD7779_1LINE = 1,

Reversed ordering in enum is not a thing I see everyday in C, maybe a bit
confusing to the reader.

> +};

Seems like it's 1:1, why enum at all?

...

> -#define AD777x_CHAN_S(index, _ext_info)					\
> +#define AD777X_CHAN_S(index, _ext_info)					\
>  	{								\
>  		.type = IIO_VOLTAGE,					\
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_CALIBSCALE)  |	\

Unneeded change.

...

> -#define AD777x_CHAN_NO_FILTER_S(index)					\
> -	AD777x_CHAN_S(index, NULL)
> +#define AD777X_CHAN_NO_FILTER_S(index)					\
> +	AD777X_CHAN_S(index, NULL)

Why?!

> +#define AD777X_CHAN_FILTER_S(index)					\
> +	AD777X_CHAN_S(index, ad7779_ext_filter)
>  
> -#define AD777x_CHAN_FILTER_S(index)					\
> -	AD777x_CHAN_S(index, ad7779_ext_filter)

Ditto.

>  static const struct iio_chan_spec ad7779_channels[] = {
> -	AD777x_CHAN_NO_FILTER_S(0),
> -	AD777x_CHAN_NO_FILTER_S(1),
> -	AD777x_CHAN_NO_FILTER_S(2),
> -	AD777x_CHAN_NO_FILTER_S(3),
> -	AD777x_CHAN_NO_FILTER_S(4),
> -	AD777x_CHAN_NO_FILTER_S(5),
> -	AD777x_CHAN_NO_FILTER_S(6),
> -	AD777x_CHAN_NO_FILTER_S(7),
> +	AD777X_CHAN_NO_FILTER_S(0),
> +	AD777X_CHAN_NO_FILTER_S(1),
> +	AD777X_CHAN_NO_FILTER_S(2),
> +	AD777X_CHAN_NO_FILTER_S(3),
> +	AD777X_CHAN_NO_FILTER_S(4),
> +	AD777X_CHAN_NO_FILTER_S(5),
> +	AD777X_CHAN_NO_FILTER_S(6),
> +	AD777X_CHAN_NO_FILTER_S(7),
>  	IIO_CHAN_SOFT_TIMESTAMP(8),
>  };

Ditto.

>  static const struct iio_chan_spec ad7779_channels_filter[] = {
> -	AD777x_CHAN_FILTER_S(0),
> -	AD777x_CHAN_FILTER_S(1),
> -	AD777x_CHAN_FILTER_S(2),
> -	AD777x_CHAN_FILTER_S(3),
> -	AD777x_CHAN_FILTER_S(4),
> -	AD777x_CHAN_FILTER_S(5),
> -	AD777x_CHAN_FILTER_S(6),
> -	AD777x_CHAN_FILTER_S(7),
> +	AD777X_CHAN_FILTER_S(0),
> +	AD777X_CHAN_FILTER_S(1),
> +	AD777X_CHAN_FILTER_S(2),
> +	AD777X_CHAN_FILTER_S(3),
> +	AD777X_CHAN_FILTER_S(4),
> +	AD777X_CHAN_FILTER_S(5),
> +	AD777X_CHAN_FILTER_S(6),
> +	AD777X_CHAN_FILTER_S(7),
>  	IIO_CHAN_SOFT_TIMESTAMP(8),
>  };

Ditto.

...

> +static int ad7779_conf_channels(struct iio_dev *indio_dev, const struct ad7779_state *st)
> +{
> +	struct iio_chan_spec *channels;
> +	struct device *dev = &st->spi->dev;
> +	int num_channels = ARRAY_SIZE(ad7779_channels);
> +
> +	channels = devm_kcalloc(dev, num_channels, sizeof(*channels), GFP_KERNEL);

Doesn't sound like a right place for devm. Is this function called only at probe stage?

> +	if (!channels)
> +		return -ENOMEM;
> +
> +	memcpy(channels, st->chip_info->channels, num_channels * sizeof(struct iio_chan_spec));

kmemdup_array()?

> +	for (int i = 0; i < 8; i++)

Why i is signed?
What is the magic 8? ARRAY_SIZE()?

> +		channels[i].scan_type.endianness = IIO_CPU;
> +
> +	indio_dev->channels = channels;
> +
> +	return 0;
> +}

...

> +	if (ret)
> +		return ret;
> +
> +	return 0;

return ...


...

> +	st->back = devm_iio_backend_get(dev, NULL);
> +	if (IS_ERR(st->back)) {
> +		dev_err_probe(dev, ret, "failed to get iio backend");

Huh?!

> +		return PTR_ERR(st->back);

Pattern is

		return dev_err_probe(...);

> +	}

-- 
With Best Regards,
Andy Shevchenko

> 
> > +static int ad7779_conf_channels(struct iio_dev *indio_dev, const struct ad7779_state *st)
> > +{
> > +	struct iio_chan_spec *channels;
> > +	struct device *dev = &st->spi->dev;
> > +	int num_channels = ARRAY_SIZE(ad7779_channels);
> > +
> > +	channels = devm_kcalloc(dev, num_channels, sizeof(*channels), GFP_KERNEL);  
> 
> Doesn't sound like a right place for devm. Is this function called only at probe stage?
Yup.  So probably wants a name that doesn't sound like a runtime thing.  setup_channels maybe?

>