[PATCH v3 RFC v3] dt-bindings: iio: adc: add ad7816/7/8 digital temperature sensor / ADC

[PATCH v3 RFC v3] dt-bindings: iio: adc: add ad7816/7/8 digital temperature sensor / ADC

[Taha Narimani]

Document the Analog Devices AD7816, AD7817, and AD7818 digital
temperature sensor and ADC bindings in YAML format.

Please note that the driver for this device is currently in drivers/staging.
This patch is sent as an RFC to clean up and standardize the device tree
bindings prior to any major driver refactoring.

While reviewing the AD7816/7/8 datasheet to correctly document the properties,
it was noted that the current staging driver attempts to request a 'busy' GPIO
for both AD7816 and AD7817. However, the AD7816 is an 8-pin device and does
not possess a BUSY pin (only the 16-pin AD7817 has it). Therefore, in this
binding, busy-gpios is strictly limited to adi,ad7817.

This resolves the checkpatch.pl warnings regarding undocumented DT
compatible strings.

Signed-off-by: Taha Narimani <tahanarimani3443@gmail.com>
---
Changes in v3:
  - Removed redundant conditional check around gpiod_get_value() as suggested by Andy Shevchenko and Dan Carpenter.
  - Switched to dev_err_probe() to avoid deferred probe spamming.
  - Introduced local struct device *dev pointer in probe and kept the GPIO request on a single line for better readability.
  - Added the missing Fixes tag requested by Jonathan Cameron.

 .../bindings/iio/adc/adi,ad7816.yaml          | 105 ++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad7816.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7816.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7816.yaml
new file mode 100644
index 0000000..48563e4
--- /dev/null
Changes in v3:
  - Removed redundant conditional check around gpiod_get_value() as suggested by Andy Shevchenko and Dan Carpenter.
  - Switched to dev_err_probe() to avoid deferred probe spamming.
  - Introduced local struct device *dev pointer in probe and kept the GPIO request on a single line for better readability.
  - Added the missing Fixes tag requested by Jonathan Cameron.

+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7816.yaml
@@ -0,0 +1,105 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,ad7816.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD7816/7/8 digital temperature sensor / ADC
+
+maintainers:
+  - Taha Narimani <tahanarimani3443@gmail.com>
+
+description: |
+  Analog Devices AD7816, AD7817, and AD7818 10-Bit general purpose ADC and
+  temperature sensor. The device communicates via an SPI interface.
+
+properties:
+  compatible:
+    enum:
+      - adi,ad7816
+      - adi,ad7817
+      - adi,ad7818
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 12500000
+
+  vdd-supply:
+    description: Main power supply.
+
+  vref-supply:
+    description: |
+      Optional external reference voltage supply. If not provided, the
+      internal reference is used. Applicable for AD7816 and AD7817.
+
+  rdwr-gpios:
+    maxItems: 1
+    description: GPIO connected to the RD/WR pin.
+
+  convert-gpios:
+    maxItems: 1
+    description: GPIO connected to the CONVST (Convert Start) pin.
+
+  busy-gpios:
+    maxItems: 1
+    description: GPIO connected to the BUSY pin. Only applicable for AD7817.
+
+  interrupts:
+    maxItems: 1
+    description: OTI (Over Temperature Indicator) interrupt. Active low.
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+  - rdwr-gpios
+  - convert-gpios
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,ad7817
+    then:
+      required:
+        - busy-gpios
+    else:
+      properties:
+        busy-gpios: false
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,ad7818
+    then:
+      properties:
+        vref-supply: false
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,ad7817";
+            reg = <0>;
+            spi-max-frequency = <1000000>;
+            vdd-supply = <&vcc>;
+            vref-supply = <&vref>;
+            rdwr-gpios = <&gpio 5 GPIO_ACTIVE_HIGH>;
+            convert-gpios = <&gpio 6 GPIO_ACTIVE_HIGH>;
+            busy-gpios = <&gpio 7 GPIO_ACTIVE_HIGH>;
+            interrupts = <20 IRQ_TYPE_LEVEL_LOW>;
+            interrupt-parent = <&gpio>;
+        };
+    };
-- 
2.53.0

[PATCH v3] staging: iio: adc: ad7816: Use devm_gpiod_get_optional() for busy GPIO

[Taha Narimani]

The driver currently utilizes devm_gpiod_get() for the 'busy' line,
which makes the GPIO mandatory. However, the busy pin is hardware-optional
depending on the specific board configuration.

Switch to devm_gpiod_get_optional() to allow boards that do not have
this pin wired up to still probe the driver successfully. Clean up
the redundant busy_pin conditional checks as gpiod_get_value() safely
handles NULL descriptors. Additionally, use dev_err_probe() to prevent
bootlog spamming during deferred probing.

Fixes: 3e5971b2ddb6 ("base: original ad7816.c")
Signed-off-by: Taha Narimani <tahanarimani3443@gmail.com>
---
Changes in v3:
  - Removed redundant conditional check around gpiod_get_value() as suggested by Andy Shevchenko and Dan Carpenter.
  - Switched to dev_err_probe() to avoid deferred probe spamming.
  - Introduced local struct device *dev pointer in probe and kept the GPIO request on a single line for better readability.
  - Added the missing Fixes tag requested by Jonathan Cameron.

 drivers/staging/iio/adc/ad7816.c | 67 +++++++++++++-------------------
 1 file changed, 28 insertions(+), 39 deletions(-)

diff --git a/drivers/staging/iio/adc/ad7816.c b/drivers/staging/iio/adc/ad7816.c
index 988eee3..807cf57 100644
--- a/drivers/staging/iio/adc/ad7816.c
Changes in v3:
  - Removed redundant conditional check around gpiod_get_value() as suggested by Andy Shevchenko and Dan Carpenter.
  - Switched to dev_err_probe() to avoid deferred probe spamming.
  - Introduced local struct device *dev pointer in probe and kept the GPIO request on a single line for better readability.
  - Added the missing Fixes tag requested by Jonathan Cameron.

+++ b/drivers/staging/iio/adc/ad7816.c
@@ -22,20 +22,20 @@
 /*
  * AD7816 config masks
  */
-#define AD7816_FULL			0x1
-#define AD7816_PD			0x2
-#define AD7816_CS_MASK			0x7
-#define AD7816_CS_MAX			0x4
+#define AD7816_FULL                     0x1
+#define AD7816_PD                       0x2
+#define AD7816_CS_MASK                  0x7
+#define AD7816_CS_MAX                   0x4
 
 /*
  * AD7816 temperature masks
  */
-#define AD7816_VALUE_OFFSET		6
-#define AD7816_BOUND_VALUE_BASE		0x8
-#define AD7816_BOUND_VALUE_MIN		-95
-#define AD7816_BOUND_VALUE_MAX		152
-#define AD7816_TEMP_FLOAT_OFFSET	2
-#define AD7816_TEMP_FLOAT_MASK		0x3
+#define AD7816_VALUE_OFFSET             6
+#define AD7816_BOUND_VALUE_BASE         0x8
+#define AD7816_BOUND_VALUE_MIN          -95
+#define AD7816_BOUND_VALUE_MAX          152
+#define AD7816_TEMP_FLOAT_OFFSET        2
+#define AD7816_TEMP_FLOAT_MASK          0x3
 
 /*
  * struct ad7816_chip_info - chip specific information
@@ -48,7 +48,7 @@ struct ad7816_chip_info {
 	struct gpio_desc *convert_pin;
 	struct gpio_desc *busy_pin;
 	u8  oti_data[AD7816_CS_MAX + 1];
-	u8  channel_id;	/* 0 always be temperature */
+	u8  channel_id; /* 0 always be temperature */
 	u8  mode;
 };
 
@@ -84,10 +84,8 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data)
 		gpiod_set_value(chip->convert_pin, 1);
 	}
 
-if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
-		while (gpiod_get_value(chip->busy_pin))
-			cpu_relax();
-	}
+	while (gpiod_get_value(chip->busy_pin))
+		cpu_relax();
 
 	gpiod_set_value(chip->rdwr_pin, 0);
 	gpiod_set_value(chip->rdwr_pin, 1);
@@ -254,8 +252,8 @@ static const struct attribute_group ad7816_attribute_group = {
  * temperature bound events
  */
 
-#define IIO_EVENT_CODE_AD7816_OTI IIO_UNMOD_EVENT_CODE(IIO_TEMP,	\
-						       0,		\
+#define IIO_EVENT_CODE_AD7816_OTI IIO_UNMOD_EVENT_CODE(IIO_TEMP,        \
+						       0,               \
 						       IIO_EV_TYPE_THRESH, \
 						       IIO_EV_DIR_FALLING)
 
@@ -351,11 +349,12 @@ static const struct iio_info ad7816_info = {
 
 static int ad7816_probe(struct spi_device *spi_dev)
 {
+	struct device *dev = &spi_dev->dev;
 	struct ad7816_chip_info *chip;
 	struct iio_dev *indio_dev;
 	int i, ret;
 
-	indio_dev = devm_iio_device_alloc(&spi_dev->dev, sizeof(*chip));
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*chip));
 	if (!indio_dev)
 		return -ENOMEM;
 	chip = iio_priv(indio_dev);
@@ -365,31 +364,22 @@ static int ad7816_probe(struct spi_device *spi_dev)
 		chip->oti_data[i] = 203;
 
 	chip->id = spi_get_device_id(spi_dev)->driver_data;
-	chip->rdwr_pin = devm_gpiod_get(&spi_dev->dev, "rdwr", GPIOD_OUT_HIGH);
+	chip->rdwr_pin = devm_gpiod_get(dev, "rdwr", GPIOD_OUT_HIGH);
 	if (IS_ERR(chip->rdwr_pin)) {
 		ret = PTR_ERR(chip->rdwr_pin);
-		dev_err(&spi_dev->dev, "Failed to request rdwr GPIO: %d\n",
-			ret);
+		dev_err(dev, "Failed to request rdwr GPIO: %d\n", ret);
 		return ret;
 	}
-	chip->convert_pin = devm_gpiod_get(&spi_dev->dev, "convert",
-					   GPIOD_OUT_HIGH);
+	chip->convert_pin = devm_gpiod_get(dev, "convert", GPIOD_OUT_HIGH);
 	if (IS_ERR(chip->convert_pin)) {
 		ret = PTR_ERR(chip->convert_pin);
-		dev_err(&spi_dev->dev, "Failed to request convert GPIO: %d\n",
-			ret);
+		dev_err(dev, "Failed to request convert GPIO: %d\n", ret);
 		return ret;
 	}
-	if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
-		chip->busy_pin = devm_gpiod_get(&spi_dev->dev, "busy",
-						GPIOD_IN);
-		if (IS_ERR(chip->busy_pin)) {
-			ret = PTR_ERR(chip->busy_pin);
-			dev_err(&spi_dev->dev, "Failed to request busy GPIO: %d\n",
-				ret);
-			return ret;
-		}
-	}
+
+	chip->busy_pin = devm_gpiod_get_optional(dev, "busy", GPIOD_IN);
+	if (IS_ERR(chip->busy_pin))
+		return dev_err_probe(dev, PTR_ERR(chip->busy_pin), "Failed to request busy GPIO\n");
 
 	indio_dev->name = spi_get_device_id(spi_dev)->name;
 	indio_dev->info = &ad7816_info;
@@ -397,7 +387,7 @@ static int ad7816_probe(struct spi_device *spi_dev)
 
 	if (spi_dev->irq) {
 		/* Only low trigger is supported in ad7816/7/8 */
-		ret = devm_request_threaded_irq(&spi_dev->dev, spi_dev->irq,
+		ret = devm_request_threaded_irq(dev, spi_dev->irq,
 						NULL,
 						&ad7816_event_handler,
 						IRQF_TRIGGER_LOW | IRQF_ONESHOT,
@@ -407,11 +397,11 @@ static int ad7816_probe(struct spi_device *spi_dev)
 			return ret;
 	}
 
-	ret = devm_iio_device_register(&spi_dev->dev, indio_dev);
+	ret = devm_iio_device_register(dev, indio_dev);
 	if (ret)
 		return ret;
 
-	dev_info(&spi_dev->dev, "%s temperature sensor and ADC registered.\n",
+	dev_info(dev, "%s temperature sensor and ADC registered.\n",
 		 indio_dev->name);
 
 	return 0;
@@ -431,7 +421,6 @@ static const struct spi_device_id ad7816_id[] = {
 	{ "ad7818", ID_AD7818 },
 	{ }
 };
-
 MODULE_DEVICE_TABLE(spi, ad7816_id);
 
 static struct spi_driver ad7816_driver = {
-- 
2.53.0

Re: [PATCH v3] staging: iio: adc: ad7816: Use devm_gpiod_get_optional() for busy GPIO

[Dan Carpenter]

On Fri, Jul 10, 2026 at 04:00:01PM +0000, Taha Narimani wrote:
>  /*
>   * struct ad7816_chip_info - chip specific information
> @@ -48,7 +48,7 @@ struct ad7816_chip_info {
>  	struct gpio_desc *convert_pin;
>  	struct gpio_desc *busy_pin;
>  	u8  oti_data[AD7816_CS_MAX + 1];
> -	u8  channel_id;	/* 0 always be temperature */
> +	u8  channel_id; /* 0 always be temperature */

What changed here??

>  	u8  mode;
>  };
>  
> @@ -84,10 +84,8 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data)
>  		gpiod_set_value(chip->convert_pin, 1);
>  	}
>  
> -if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
> -		while (gpiod_get_value(chip->busy_pin))
> -			cpu_relax();

This patch doesn't apply.  Not sure what went wrong but maybe it's
related to this?

> -	}
> +	while (gpiod_get_value(chip->busy_pin))
> +		cpu_relax();
>  
>  	gpiod_set_value(chip->rdwr_pin, 0);
>  	gpiod_set_value(chip->rdwr_pin, 1);

regards,
dan carpenter

Re: [PATCH v3] staging: iio: adc: ad7816: Use devm_gpiod_get_optional() for busy GPIO

[Maxwell Doose]

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Hi Taha,

On Fri Jul 10, 2026 at 11:00 AM CDT
Taha Narimani <tahanarimani3443@gmail.com> wrote:

> The driver currently utilizes devm_gpiod_get() for the 'busy' line,
> which makes the GPIO mandatory. However, the busy pin is hardware-optional
> depending on the specific board configuration.
>
> Switch to devm_gpiod_get_optional() to allow boards that do not have
> this pin wired up to still probe the driver successfully. Clean up
> the redundant busy_pin conditional checks as gpiod_get_value() safely
> handles NULL descriptors. Additionally, use dev_err_probe() to prevent
> bootlog spamming during deferred probing.
>
> Fixes: 3e5971b2ddb6 ("base: original ad7816.c")

If this is a fix, then why are we making style changes?

> Signed-off-by: Taha Narimani <tahanarimani3443@gmail.com>
> ---
> Changes in v3:
>   - Removed redundant conditional check around gpiod_get_value() as suggested by Andy Shevchenko and Dan Carpenter.
>   - Switched to dev_err_probe() to avoid deferred probe spamming.
>   - Introduced local struct device *dev pointer in probe and kept the GPIO request on a single line for better readability.

Unless someone requested this during review this doesn't make sense.
Please see my above comment, and I'd also suggest to take a look at
Documentation/process/submitting-patches.rst.

>   - Added the missing Fixes tag requested by Jonathan Cameron.
>
>  drivers/staging/iio/adc/ad7816.c | 67 +++++++++++++-------------------
>  1 file changed, 28 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/staging/iio/adc/ad7816.c b/drivers/staging/iio/adc/ad7816.c
> index 988eee3..807cf57 100644
> --- a/drivers/staging/iio/adc/ad7816.c
> Changes in v3:
>   - Removed redundant conditional check around gpiod_get_value() as suggested by Andy Shevchenko and Dan Carpenter.
>   - Switched to dev_err_probe() to avoid deferred probe spamming.
>   - Introduced local struct device *dev pointer in probe and kept the GPIO request on a single line for better readability.
>   - Added the missing Fixes tag requested by Jonathan Cameron.
>

Wrong spot for this + causes the patch to not apply. It should be below
the --- right after the list of tags.

> +++ b/drivers/staging/iio/adc/ad7816.c
> @@ -22,20 +22,20 @@
>  /*
>   * AD7816 config masks
>   */
> -#define AD7816_FULL			0x1
> -#define AD7816_PD			0x2
> -#define AD7816_CS_MASK			0x7
> -#define AD7816_CS_MAX			0x4
> +#define AD7816_FULL                     0x1
> +#define AD7816_PD                       0x2
> +#define AD7816_CS_MASK                  0x7
> +#define AD7816_CS_MAX                   0x4
>  

Nothing changed? Seems like a stray change.

>  /*
>   * AD7816 temperature masks
>   */
> -#define AD7816_VALUE_OFFSET		6
> -#define AD7816_BOUND_VALUE_BASE		0x8
> -#define AD7816_BOUND_VALUE_MIN		-95
> -#define AD7816_BOUND_VALUE_MAX		152
> -#define AD7816_TEMP_FLOAT_OFFSET	2
> -#define AD7816_TEMP_FLOAT_MASK		0x3
> +#define AD7816_VALUE_OFFSET             6
> +#define AD7816_BOUND_VALUE_BASE         0x8
> +#define AD7816_BOUND_VALUE_MIN          -95
> +#define AD7816_BOUND_VALUE_MAX          152
> +#define AD7816_TEMP_FLOAT_OFFSET        2
> +#define AD7816_TEMP_FLOAT_MASK          0x3
>  

Ditto.

>  /*
>   * struct ad7816_chip_info - chip specific information
> @@ -48,7 +48,7 @@ struct ad7816_chip_info {
>  	struct gpio_desc *convert_pin;
>  	struct gpio_desc *busy_pin;
>  	u8  oti_data[AD7816_CS_MAX + 1];
> -	u8  channel_id;	/* 0 always be temperature */
> +	u8  channel_id; /* 0 always be temperature */
>  	u8  mode;
>  };
>  

Here as well.

> @@ -84,10 +84,8 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data)
>  		gpiod_set_value(chip->convert_pin, 1);
>  	}
>  
> -if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
> -		while (gpiod_get_value(chip->busy_pin))
> -			cpu_relax();
> -	}
> +	while (gpiod_get_value(chip->busy_pin))
> +		cpu_relax();
>

Can you explain why we're removing this check? There also seems to be a
spot in _probe() where the check gets removed as well.

>  	gpiod_set_value(chip->rdwr_pin, 0);
>  	gpiod_set_value(chip->rdwr_pin, 1);
> @@ -254,8 +252,8 @@ static const struct attribute_group ad7816_attribute_group = {
>   * temperature bound events
>   */
>  
> -#define IIO_EVENT_CODE_AD7816_OTI IIO_UNMOD_EVENT_CODE(IIO_TEMP,	\
> -						       0,		\
> +#define IIO_EVENT_CODE_AD7816_OTI IIO_UNMOD_EVENT_CODE(IIO_TEMP,        \
> +						       0,               \
>  						       IIO_EV_TYPE_THRESH, \
>  						       IIO_EV_DIR_FALLING)
>  

Seems like another stray change.

> @@ -351,11 +349,12 @@ static const struct iio_info ad7816_info = {
>  
>  static int ad7816_probe(struct spi_device *spi_dev)
>  {
> +	struct device *dev = &spi_dev->dev;

Again, why are we doing style changes? This seems to be a fix instead of
a style patch.

>  	struct ad7816_chip_info *chip;
>  	struct iio_dev *indio_dev;
>  	int i, ret;
>  
> -	indio_dev = devm_iio_device_alloc(&spi_dev->dev, sizeof(*chip));
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*chip));
>  	if (!indio_dev)
>  		return -ENOMEM;
>  	chip = iio_priv(indio_dev);

...

> @@ -431,7 +421,6 @@ static const struct spi_device_id ad7816_id[] = {
>  	{ "ad7818", ID_AD7818 },
>  	{ }
>  };
> -

Stray change.

>  MODULE_DEVICE_TABLE(spi, ad7816_id);
>  
>  static struct spi_driver ad7816_driver = {


-- 
best regards,
max


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Re: [PATCH v3 RFC v3] dt-bindings: iio: adc: add ad7816/7/8 digital temperature sensor / ADC

[Krzysztof Kozlowski]

On 10/07/2026 18:00, Taha Narimani wrote:
> Document the Analog Devices AD7816, AD7817, and AD7818 digital
> temperature sensor and ADC bindings in YAML format.
> 
> Please note that the driver for this device is currently in drivers/staging.

So you should not send it.


> This patch is sent as an RFC to clean up and standardize the device tree
> bindings prior to any major driver refactoring.
> 
> While reviewing the AD7816/7/8 datasheet to correctly document the properties,
> it was noted that the current staging driver attempts to request a 'busy' GPIO
> for both AD7816 and AD7817. However, the AD7816 is an 8-pin device and does
> not possess a BUSY pin (only the 16-pin AD7817 has it). Therefore, in this
> binding, busy-gpios is strictly limited to adi,ad7817.
> 
> This resolves the checkpatch.pl warnings regarding undocumented DT
> compatible strings.

That's not necessary.

Best regards,
Krzysztof