[PATCH v4 0/4] Add IIO backend support for AD7779

[PATCH v4 0/4] Add IIO backend support for AD7779

[Ioana Risteiu]

  - Add axi_adc_num_lanes_set in the adi_axi_adc_ops structure to support
  setting number of lanes used by AXI ADC.
  - Add the generic io-backends property to the AD7779 binding to enable
  support for the IIO backend framework.
  - Add the adi,num-lanes property to set the number of lanes used by
  AD7779.
  - Move the initialization specific to communication without iio-backend
  into a separate setup function.
  - Add a new functionality to ad7779 driver that streams data through data
  output interface using IIO backend interface.

Ioana Risteiu (4):
  iio: adc: adi-axi-adc: add axi_adc_num_lanes_set
  dt-bindings: iio: adc: add IIO backend support
  iio: adc: extract setup function without backend
  iio: adc: update ad7779 to use IIO backend

 .../bindings/iio/adc/adi,ad7779.yaml          |  44 +++-
 drivers/iio/adc/ad7779.c                      | 197 ++++++++++++++----
 drivers/iio/adc/adi-axi-adc.c                 |   1 +
 3 files changed, 203 insertions(+), 39 deletions(-)

-- 
2.47.2

[PATCH v4 1/4] iio: adc: adi-axi-adc: add axi_adc_num_lanes_set

[Ioana Risteiu]

Add axi_adc_num_lanes_set in the adi_axi_adc_ops structure to support
setting number of lanes used by AXI ADC. This operation is included in
the generic structure because the number of lanes is a configurable
parameter of the generic AXI ADC IP core, not specific to a device.

Signed-off-by: Ioana Risteiu <Ioana.Risteiu@analog.com>
---
changes in v4:
 - improved patch description
 drivers/iio/adc/adi-axi-adc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
index 2d86bb0e08a7..20bb59c24acf 100644
--- a/drivers/iio/adc/adi-axi-adc.c
+++ b/drivers/iio/adc/adi-axi-adc.c
@@ -617,6 +617,7 @@ static const struct iio_backend_ops adi_axi_adc_ops = {
 	.chan_status = axi_adc_chan_status,
 	.interface_type_get = axi_adc_interface_type_get,
 	.oversampling_ratio_set = axi_adc_oversampling_ratio_set,
+	.num_lanes_set = axi_adc_num_lanes_set,
 	.debugfs_reg_access = iio_backend_debugfs_ptr(axi_adc_reg_access),
 	.debugfs_print_chan_status = iio_backend_debugfs_ptr(axi_adc_debugfs_print_chan_status),
 };
-- 
2.47.2

[PATCH v4 2/4] dt-bindings: iio: adc: add IIO backend support

[Ioana Risteiu]

Add the generic io-backends property to the AD7779 binding to enable
support for the IIO backend framework.

Also add the adi,num-lanes property to set the number of lanes used by
AD7779.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Ioana Risteiu <Ioana.Risteiu@analog.com>
---
changes in v4:
 - included previously omitted reviewers from earlier patches
 - modified the logic for handling adi,num-lanes in devicetree
 .../bindings/iio/adc/adi,ad7779.yaml          | 44 ++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7779.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7779.yaml
index 044f92f39cfa..ba3f7b2bd6cf 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7779.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7779.yaml
@@ -80,11 +80,36 @@ properties:
   reset-gpios:
     maxItems: 1
 
+  io-backends:
+    maxItems: 1
+
+  adi,num-lanes:
+    description:
+      Number of lanes on which the data is sent on the output when the data
+      output interface is used.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [1, 2, 4]
+    default: 4
+
 required:
   - compatible
   - reg
   - clocks
-  - interrupts
+
+allOf:
+  - if:
+      not:
+        required:
+          - io-backends
+    then:
+      properties:
+        adi,num-lanes: false
+
+oneOf:
+  - required:
+      - interrupts
+  - required:
+      - io-backends
 
 unevaluatedProperties: false
 
@@ -107,4 +132,21 @@ examples:
           clocks = <&adc_clk>;
         };
     };
+
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+          compatible = "adi,ad7779";
+          reg = <0>;
+          start-gpios = <&gpio0 87 GPIO_ACTIVE_LOW>;
+          reset-gpios = <&gpio0 93 GPIO_ACTIVE_LOW>;
+          clocks = <&adc_clk>;
+          io-backends = <&iio_backend>;
+          adi,num-lanes = <4>;
+        };
+    };
 ...
-- 
2.47.2

[PATCH v4 3/4] iio: adc: extract setup function without backend

[Ioana Risteiu]

Refactor probe function by moving the initialization specific to
communication without iio-backend into a separate setup function.

The purpose of this modification is better code organization. No
functional changes intended.

Signed-off-by: Ioana Risteiu <Ioana.Risteiu@analog.com>
---
no changes in v4.
 drivers/iio/adc/ad7779.c | 83 ++++++++++++++++++++++------------------
 1 file changed, 45 insertions(+), 38 deletions(-)

diff --git a/drivers/iio/adc/ad7779.c b/drivers/iio/adc/ad7779.c
index 845adc510239..f7e681c0e8c0 100644
--- a/drivers/iio/adc/ad7779.c
+++ b/drivers/iio/adc/ad7779.c
@@ -752,6 +752,50 @@ static int ad7779_conf(struct ad7779_state *st, struct gpio_desc *start_gpio)
 	return 0;
 }
 
+static int ad7779_setup_without_backend(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;
+
+	return ad7779_spi_write_mask(st, AD7779_REG_DOUT_FORMAT,
+				    AD7779_DCLK_CLK_DIV_MSK,
+				    FIELD_PREP(AD7779_DCLK_CLK_DIV_MSK, 7));
+}
+
 static int ad7779_probe(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev;
@@ -760,9 +804,6 @@ 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 +845,11 @@ 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;
+	ret = ad7779_setup_without_backend(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;
 
-- 
2.47.2

[PATCH v4 4/4] iio: adc: update ad7779 to use IIO backend

[Ioana Risteiu]

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 v4:
 - grouped includes in alphabetical order
 - reordered fields in struct ad7779_state
 - modified logic of setting the number of lanes 
 - validating devicetree value
 drivers/iio/adc/ad7779.c | 116 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 115 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7779.c b/drivers/iio/adc/ad7779.c
index f7e681c0e8c0..adca490061c9 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 +786,49 @@ 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 = -EINVAL;
+
+	if (num_lanes != AD7779_1LINE &&
+		num_lanes != AD7779_2LINES &&
+		num_lanes != AD7779_4LINES)
+		return 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_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 (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 +873,39 @@ 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 = -EINVAL;
+	int 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 +958,10 @@ 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;
@@ -943,3 +1056,4 @@ 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

Re: [PATCH v4 3/4] iio: adc: extract setup function without backend

[Andy Shevchenko]

On Wed, Aug 20, 2025 at 03:02:44PM +0300, Ioana Risteiu wrote:
> Refactor probe function by moving the initialization specific to
> communication without iio-backend into a separate setup function.
> 
> The purpose of this modification is better code organization. No
> functional changes intended.

...

> +	if (ret)
> +		return dev_err_probe(dev, ret, "request IRQ %d failed\n",
> +					st->spi->irq);

Something went wrong with the indentation.

...

> +	ret = ad7779_setup_without_backend(st, indio_dev);

>  

Now we have redundant blank line here, please remove it.

>  	if (ret)
>  		return ret;

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 1/4] iio: adc: adi-axi-adc: add axi_adc_num_lanes_set

[Andy Shevchenko]

On Wed, Aug 20, 2025 at 03:02:42PM +0300, Ioana Risteiu wrote:
> Add axi_adc_num_lanes_set in the adi_axi_adc_ops structure to support

axi_adc_num_lanes_set()

or I think even better to rephrase

"Assign num_lanes_set in the adi_axi_adc_ops to axi_adc_num_lanes_set()..."

> setting number of lanes used by AXI ADC. This operation is included in
> the generic structure because the number of lanes is a configurable
> parameter of the generic AXI ADC IP core, not specific to a device.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 4/4] iio: adc: update ad7779 to use IIO backend

[Andy Shevchenko]

On Wed, Aug 20, 2025 at 03:02:45PM +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,
> +				 unsigned int num_lanes)
> +{
> +	struct ad7779_state *st = iio_priv(indio_dev);

> +	int ret = -EINVAL;

In general the split assignment is easier to maintain and less prone to subtle
errors. In this case it's even worse as it's not needed...

> +	if (num_lanes != AD7779_1LINE &&
> +		num_lanes != AD7779_2LINES &&
> +		num_lanes != AD7779_4LINES)
> +		return ret;

...just return the error code directly here.

> +	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);

Indentation...

> +	if (!channels)
> +		return -ENOMEM;
> +
> +	for (int i = 0; i < ARRAY_SIZE(ad7779_channels); i++)

Why signed iterator?

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

...

> +static int ad7779_setup_backend(struct ad7779_state *st, struct iio_dev *indio_dev)
> +{
> +	struct device *dev = &st->spi->dev;

> +	int ret = -EINVAL;

Why?!

> +	int num_lanes;

Can it be negatie?

> +	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);
> +}

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 4/4] iio: adc: update ad7779 to use IIO backend

[Jonathan Cameron]

On Wed, 20 Aug 2025 17:18:05 +0300
Andy Shevchenko <andriy.shevchenko@intel.com> wrote:

> On Wed, Aug 20, 2025 at 03:02:45PM +0300, Ioana Risteiu wrote:
> > Add a new functionality to ad7779 driver that streams data through data
> > output interface using IIO backend interface.  

A few follow ups from me.

Jonathan

> ...
> 
> > +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 = -EINVAL;  
> 
> In general the split assignment is easier to maintain and less prone to subtle
> errors. In this case it's even worse as it's not needed...
> 
> > +	if (num_lanes != AD7779_1LINE &&
> > +		num_lanes != AD7779_2LINES &&
> > +		num_lanes != AD7779_4LINES)
> > +		return ret;  
> 
> ...just return the error code directly here.

Those enum values in general seem like a bad idea.  Just use numbers.
If the enum was used as a type it would be a different situation but here it
is used as a glorified way to give the 1 lane to the value 1 etc which just
makes it harder to read.


> 
> > +	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);  
> 
> Indentation...
> 
> > +	if (!channels)
> > +		return -ENOMEM;
> > +
> > +	for (int i = 0; i < ARRAY_SIZE(ad7779_channels); i++)  
> 
> Why signed iterator?
> 
> > +		channels[i].scan_type.endianness = IIO_CPU;
> > +
> > +	indio_dev->channels = channels;
> > +
> > +	return 0;
> > +}  
> 
> ...
> 
> > +static int ad7779_setup_backend(struct ad7779_state *st, struct iio_dev *indio_dev)
> > +{
> > +	struct device *dev = &st->spi->dev;  
> 
> > +	int ret = -EINVAL;  
> 
> Why?!
> 
> > +	int num_lanes;  
> 
> Can it be negatie?

Good spot.

Even beyond sign it needs to be a u32 given how it is used.

> 
> > +	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);
> > +}  
>