[PATCH 0/2] iio: adc: add max11205 adc driver

[PATCH 0/2] iio: adc: add max11205 adc driver

[Ramona Bolboaca]

Adding support for max11205 16-bit single-channel ultra-low power
delta-sigma adc.
The MAX11205 is compatible with the 2-wire interface and uses
SCLK and RDY/DOUT for serial communica- tions. In this mode, all
controls are implemented by tim- ing the high or low phase of the SCLK.
The 2-wire serial interface only allows for data to be read out through the
RDY/DOUT output.

Ramona Bolboaca (2):
  bindings: iio: adc: Add max11205 documentation file
  iio: adc: add max11205 adc driver

 .../bindings/iio/adc/maxim,max11205.yaml      |  65 ++++++
 MAINTAINERS                                   |   8 +
 drivers/iio/adc/Kconfig                       |  14 ++
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/max11205.c                    | 192 ++++++++++++++++++
 5 files changed, 280 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
 create mode 100644 drivers/iio/adc/max11205.c

-- 
2.25.1

[PATCH 1/2] bindings: iio: adc: Add max11205 documentation file

[Ramona Bolboaca]

Add bindings documentation file and MAINTAINERS entry for MAX11205.

Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
---
 .../bindings/iio/adc/maxim,max11205.yaml      | 65 +++++++++++++++++++
 MAINTAINERS                                   |  8 +++
 2 files changed, 73 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml b/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
new file mode 100644
index 000000000000..bddd18a44969
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/maxim,max11205.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim MAX11205 ADC
+
+maintainers:
+  - Ramona Bolboaca <ramona.bolboaca@analog.com>
+
+description: |
+  The MAX11205 is an ultra-low-power (< 300FA max
+  active current), high-resolution, serial-output ADC.
+
+  https://datasheets.maximintegrated.com/en/ds/MAX11205.pdf
+
+properties:
+  compatible:
+    enum:
+      - maxim,max11205a
+      - maxim,max11205b
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 5000000
+
+  spi-cpha: true
+
+  vref-supply:
+    description:
+      The regulator supply for the ADC reference voltage.
+
+required:
+  - compatible
+  - reg
+  - spi-max-frequency
+  - spi-cpha
+  - interrupts
+  - vref-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        max11205@0 {
+                      compatible = "maxim,max11205a";
+                      reg = <0>;
+                      spi-max-frequency = <5000000>;
+                      spi-cpha;
+                      interrupt-parent = <&gpio>;
+                      interrupts = <19 IRQ_TYPE_EDGE_FALLING>;
+                      vref-supply = <&max11205_vref>;
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index 96f47a7865d6..db1b5dc03988 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12341,6 +12341,14 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/iio/proximity/maxbotix,mb1232.yaml
 F:	drivers/iio/proximity/mb1232.c
 
+MAXIM MAX11205 DRIVER
+M:	Ramona Bolboaca <ramona.bolboaca@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
+F:	drivers/iio/adc/max11205.c
+
 MAXIM MAX17040 FAMILY FUEL GAUGE DRIVERS
 R:	Iskren Chernev <iskren.chernev@gmail.com>
 R:	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
-- 
2.25.1

[PATCH 2/2] iio: adc: add max11205 adc driver

[Ramona Bolboaca]

Adding support for max11205 16-bit single-channel ultra-low power
delta-sigma adc.
The MAX11205 is compatible with the 2-wire interface and uses
SCLK and RDY/DOUT for serial communica- tions. In this mode, all
controls are implemented by tim- ing the high or low phase of the SCLK.
The 2-wire serial interface only allows for data to be read out through the
RDY/DOUT output.

Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX11205.pdf
Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
---
 drivers/iio/adc/Kconfig    |  14 +++
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/max11205.c | 192 +++++++++++++++++++++++++++++++++++++
 3 files changed, 207 insertions(+)
 create mode 100644 drivers/iio/adc/max11205.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 7fe5930891e0..f0de4516a302 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -653,6 +653,20 @@ config MAX1118
 	  To compile this driver as a module, choose M here: the module will be
 	  called max1118.
 
+config MAX11205
+	tristate "Maxim max11205 ADC driver"
+	depends on SPI
+	select AD_SIGMA_DELTA
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+
+	help
+	  Say yes here to build support for Maxim max11205
+	  16-bit, single-channel ultra-low power delta-sigma ADC.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max11205.
+
 config MAX1241
 	tristate "Maxim max1241 ADC driver"
 	depends on SPI_MASTER
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 1772a549a3c8..bb681844e497 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_LTC2497) += ltc2497.o ltc2497-core.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX11100) += max11100.o
 obj-$(CONFIG_MAX1118) += max1118.o
+obj-$(CONFIG_MAX11205) += max11205.o
 obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
 obj-$(CONFIG_MAX9611) += max9611.o
diff --git a/drivers/iio/adc/max11205.c b/drivers/iio/adc/max11205.c
new file mode 100644
index 000000000000..b2d9f9085fde
--- /dev/null
+++ b/drivers/iio/adc/max11205.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max11205 16-Bit Delta-Sigma ADC
+ *
+ * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-max11205.pdf
+ * Copyright (C) 2022 Analog Devices, Inc.
+ * Author: Ramona Bolboaca <ramona.bolboaca@analog.com>
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/adc/ad_sigma_delta.h>
+
+#define MAX11205_BIT_SCALE	15
+#define MAX11205A_OUT_DATA_RATE	116
+#define MAX11205B_OUT_DATA_RATE	13
+
+enum chip_type {
+	TYPE_MAX11205A,
+	TYPE_MAX11205B,
+};
+
+struct chip_info {
+	unsigned int	out_data_rate;
+	const char	*name;
+};
+
+struct max11205_state {
+	const struct chip_info	*chip_info;
+	struct regulator	*vref;
+	struct ad_sigma_delta	sd;
+};
+
+static const struct ad_sigma_delta_info max11205_sigma_delta_info = {
+	.has_registers = false,
+	.irq_flags = IRQF_TRIGGER_FALLING,
+};
+
+static int max11205_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max11205_state *st = iio_priv(indio_dev);
+	int reg_mv;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		return ad_sigma_delta_single_conversion(indio_dev, chan, val);
+	case IIO_CHAN_INFO_SCALE:
+		reg_mv = regulator_get_voltage(st->vref);
+		if (reg_mv < 0)
+			return reg_mv;
+		reg_mv /= 1000;
+		*val = reg_mv;
+		*val2 = MAX11205_BIT_SCALE;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*val = st->chip_info->out_data_rate;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info max11205_iio_info = {
+	.read_raw = max11205_read_raw,
+	.validate_trigger = ad_sd_validate_trigger,
+};
+
+static const struct iio_chan_spec max11205_channels[] = {
+	{
+		.type = IIO_VOLTAGE,
+		.indexed = 1,
+		.scan_type = {
+			.sign = 's',
+			.realbits = 16,
+			.storagebits = 16,
+			.endianness = IIO_BE
+		},
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+		BIT(IIO_CHAN_INFO_SAMP_FREQ) |
+		BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static void max11205_reg_disable(void *reg)
+{
+	regulator_disable(reg);
+}
+
+static int max11205_probe(struct spi_device *spi)
+{
+	struct max11205_state *st;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+
+	ad_sd_init(&st->sd, indio_dev, spi, &max11205_sigma_delta_info);
+
+	st->chip_info = device_get_match_data(&spi->dev);
+
+	indio_dev->name = st->chip_info->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = max11205_channels;
+	indio_dev->num_channels = 1;
+	indio_dev->info = &max11205_iio_info;
+
+	st->vref = devm_regulator_get(&spi->dev, "vref");
+	if (IS_ERR(st->vref))
+		return dev_err_probe(&spi->dev, PTR_ERR(st->vref),
+				     "Failed to get vref regulator\n");
+
+	ret = regulator_enable(st->vref);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(&spi->dev, max11205_reg_disable, st->vref);
+	if (ret)
+		return ret;
+
+	ret = devm_ad_sd_setup_buffer_and_trigger(&spi->dev, indio_dev);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static void max11205_remove(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev = spi_get_drvdata(spi);
+	struct max11205_state *st = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	regulator_disable(st->vref);
+}
+
+static const struct spi_device_id max11205_spi_ids[] = {
+	{"max11205a", TYPE_MAX11205A},
+	{"max11205b", TYPE_MAX11205B},
+	{}
+};
+MODULE_DEVICE_TABLE(spi, max11205_spi_ids);
+
+static const struct chip_info max11205_chip_info[] = {
+	[TYPE_MAX11205A] = {
+		.out_data_rate = MAX11205A_OUT_DATA_RATE,
+		.name = "max11205a"
+	},
+	[TYPE_MAX11205B] = {
+		.out_data_rate = MAX11205B_OUT_DATA_RATE,
+		.name = "max11205b"
+	}
+};
+
+static const struct of_device_id max11205_dt_ids[] = {
+	{
+		.compatible = "maxim,max11205a",
+		.data = &max11205_chip_info[TYPE_MAX11205A],
+	},
+	{
+		.compatible = "maxim,max11205b",
+		.data = &max11205_chip_info[TYPE_MAX11205B],
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, max11205_dt_ids);
+
+static struct spi_driver max11205_spi_driver = {
+	.driver = {
+		.name = "max11205",
+		.of_match_table = max11205_dt_ids,
+	},
+	.probe = max11205_probe,
+	.remove = max11205_remove,
+	.id_table = max11205_spi_ids,
+};
+
+module_spi_driver(max11205_spi_driver);
+
+MODULE_AUTHOR("Ramona Bolboaca <ramona.bolboaca@analog.com>");
+MODULE_DESCRIPTION("MAX11205 ADC driver");
+MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS(IIO_AD_SIGMA_DELTA);
-- 
2.25.1

Re: [PATCH 1/2] bindings: iio: adc: Add max11205 documentation file

[Krzysztof Kozlowski]

On 24/08/2022 15:52, Ramona Bolboaca wrote:
> Add bindings documentation file and MAINTAINERS entry for MAX11205.
> 
> Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
> ---
>  .../bindings/iio/adc/maxim,max11205.yaml      | 65 +++++++++++++++++++
>  MAINTAINERS                                   |  8 +++
>  2 files changed, 73 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml b/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
> new file mode 100644
> index 000000000000..bddd18a44969
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
> @@ -0,0 +1,65 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/maxim,max11205.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Maxim MAX11205 ADC
> +
> +maintainers:
> +  - Ramona Bolboaca <ramona.bolboaca@analog.com>
> +
> +description: |
> +  The MAX11205 is an ultra-low-power (< 300FA max
> +  active current), high-resolution, serial-output ADC.
> +
> +  https://datasheets.maximintegrated.com/en/ds/MAX11205.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - maxim,max11205a
> +      - maxim,max11205b
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  spi-max-frequency:
> +    maximum: 5000000
> +
> +  spi-cpha: true

Both properties are good, but still you should reference
/schemas/spi/spi-peripheral-props.yaml in allOf and use
unevaluatedProperties:false. See other bindings for SPI devices.

> +
> +  vref-supply:
> +    description:
> +      The regulator supply for the ADC reference voltage.
> +
> +required:
> +  - compatible
> +  - reg
> +  - spi-max-frequency
> +  - spi-cpha
> +  - interrupts
> +  - vref-supply
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        max11205@0 {

adc
Node names should be generic.
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

> +                      compatible = "maxim,max11205a";

Messed up indentation. Use 4 spaces.

> +                      reg = <0>;
> +                      spi-max-frequency = <5000000>;
> +                      spi-cpha;

Best regards,
Krzysztof

Re: [PATCH 2/2] iio: adc: add max11205 adc driver

[Andy Shevchenko]

On Wed, Aug 24, 2022 at 3:56 PM Ramona Bolboaca
<ramona.bolboaca@analog.com> wrote:
>
> Adding support for max11205 16-bit single-channel ultra-low power
> delta-sigma adc.
> The MAX11205 is compatible with the 2-wire interface and uses
> SCLK and RDY/DOUT for serial communica- tions. In this mode, all
> controls are implemented by tim- ing the high or low phase of the SCLK.
> The 2-wire serial interface only allows for data to be read out through the
> RDY/DOUT output.

Is there any existing driver that can be extended to support this chip?

...

> +       st->chip_info = device_get_match_data(&spi->dev);

And if chip_info is NULL?

...

> +static void max11205_remove(struct spi_device *spi)
> +{
> +       struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +       struct max11205_state *st = iio_priv(indio_dev);

> +       iio_device_unregister(indio_dev);
> +       regulator_disable(st->vref);
> +}

Have you tested module removal?

> +

...

> +static const struct chip_info max11205_chip_info[] = {
> +       [TYPE_MAX11205A] = {
> +               .out_data_rate = MAX11205A_OUT_DATA_RATE,

> +               .name = "max11205a"

+ Comma

> +       },
> +       [TYPE_MAX11205B] = {
> +               .out_data_rate = MAX11205B_OUT_DATA_RATE,

> +               .name = "max11205b"

Ditto.

> +       }

Ditto.

> +};

...

> +

Redundant blank line.

> +module_spi_driver(max11205_spi_driver);

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2] bindings: iio: adc: Add max11205 documentation file

[Jonathan Cameron]

On Wed, 24 Aug 2022 15:52:02 +0300
Ramona Bolboaca <ramona.bolboaca@analog.com> wrote:

> Add bindings documentation file and MAINTAINERS entry for MAX11205.
> 
> Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
Hi Ramona,

Welcome to IIO. 

A few comments inline to add to what Krzysztof sent.

Thanks,

Jonathan

> ---
>  .../bindings/iio/adc/maxim,max11205.yaml      | 65 +++++++++++++++++++
>  MAINTAINERS                                   |  8 +++
>  2 files changed, 73 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml b/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
> new file mode 100644
> index 000000000000..bddd18a44969
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
> @@ -0,0 +1,65 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/maxim,max11205.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Maxim MAX11205 ADC
> +
> +maintainers:
> +  - Ramona Bolboaca <ramona.bolboaca@analog.com>
> +
> +description: |
> +  The MAX11205 is an ultra-low-power (< 300FA max
> +  active current), high-resolution, serial-output ADC.

Wrap lines nearer to 75-80 chars.

> +
> +  https://datasheets.maximintegrated.com/en/ds/MAX11205.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - maxim,max11205a
> +      - maxim,max11205b
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  spi-max-frequency:
> +    maximum: 5000000
> +
> +  spi-cpha: true
> +
> +  vref-supply:
> +    description:
> +      The regulator supply for the ADC reference voltage.

Might be worth mentioning it's a differential reference. I'm not 100% sure
how we handle those...  I guess as a regulator, but it's a little unusual.

Jonathan

> +
> +required:
> +  - compatible
> +  - reg
> +  - spi-max-frequency
> +  - spi-cpha
> +  - interrupts
> +  - vref-supply
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        max11205@0 {
> +                      compatible = "maxim,max11205a";
> +                      reg = <0>;
> +                      spi-max-frequency = <5000000>;
> +                      spi-cpha;
> +                      interrupt-parent = <&gpio>;
> +                      interrupts = <19 IRQ_TYPE_EDGE_FALLING>;
> +                      vref-supply = <&max11205_vref>;
> +        };
> +    };
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 96f47a7865d6..db1b5dc03988 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12341,6 +12341,14 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/iio/proximity/maxbotix,mb1232.yaml
>  F:	drivers/iio/proximity/mb1232.c
>  
> +MAXIM MAX11205 DRIVER
> +M:	Ramona Bolboaca <ramona.bolboaca@analog.com>
> +L:	linux-iio@vger.kernel.org
> +S:	Supported
> +W:	https://ez.analog.com/linux-software-drivers
> +F:	Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
> +F:	drivers/iio/adc/max11205.c
> +
>  MAXIM MAX17040 FAMILY FUEL GAUGE DRIVERS
>  R:	Iskren Chernev <iskren.chernev@gmail.com>
>  R:	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Re: [PATCH 2/2] iio: adc: add max11205 adc driver

[Jonathan Cameron]

On Wed, 24 Aug 2022 15:52:03 +0300
Ramona Bolboaca <ramona.bolboaca@analog.com> wrote:

> Adding support for max11205 16-bit single-channel ultra-low power
> delta-sigma adc.
> The MAX11205 is compatible with the 2-wire interface and uses
> SCLK and RDY/DOUT for serial communica- tions. In this mode, all
> controls are implemented by tim- ing the high or low phase of the SCLK.
> The 2-wire serial interface only allows for data to be read out through the
> RDY/DOUT output.
> 
> Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX11205.pdf
> Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
A few additional comments from me.

Jonathan

> ---
>  drivers/iio/adc/Kconfig    |  14 +++
>  drivers/iio/adc/Makefile   |   1 +
>  drivers/iio/adc/max11205.c | 192 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 207 insertions(+)
>  create mode 100644 drivers/iio/adc/max11205.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 7fe5930891e0..f0de4516a302 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -653,6 +653,20 @@ config MAX1118
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called max1118.
>  
> +config MAX11205
> +	tristate "Maxim max11205 ADC driver"
> +	depends on SPI
> +	select AD_SIGMA_DELTA
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +
> +	help
> +	  Say yes here to build support for Maxim max11205
> +	  16-bit, single-channel ultra-low power delta-sigma ADC.

Wrap consistently to 75-80 chars.

> +
> +	  To compile this driver as a module, choose M here: the module will be
> +	  called max11205.
> +
>  config MAX1241
>  	tristate "Maxim max1241 ADC driver"
>  	depends on SPI_MASTER

...

> diff --git a/drivers/iio/adc/max11205.c b/drivers/iio/adc/max11205.c
> new file mode 100644
> index 000000000000..b2d9f9085fde
> --- /dev/null
> +++ b/drivers/iio/adc/max11205.c
> @@ -0,0 +1,192 @@


> +static const struct ad_sigma_delta_info max11205_sigma_delta_info = {
> +	.has_registers = false,
> +	.irq_flags = IRQF_TRIGGER_FALLING,

Generally IRQ direction should come from firmware (dt etc) as, just because
a device will only provide a particular type of interrupt, it's possible
the board designer did some cheap level conversion or interupt sharing
by putting an inverter in the path to the SoC pin.

We have some historical drivers where we hard coded it (and now can't
change that as there may be boards relying on it) but if possible
avoid introducing it for new drivers.

> +};
,,,

>
> +
> +static void max11205_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +	struct max11205_state *st = iio_priv(indio_dev);
> +
> +	iio_device_unregister(indio_dev);

As Andy pointed out you have an issue here. Make sure you understand
what the devm_ device managed framework does.


> +	regulator_disable(st->vref);
> +}
> +
> +static const struct spi_device_id max11205_spi_ids[] = {
> +	{"max11205a", TYPE_MAX11205A},
Prefer space after { and before }

	{ "max11205a, TYPE_MAX11205A }, 

Driver doesn't currently support using this probing method though
for a reason that Andy raised.

> +	{"max11205b", TYPE_MAX11205B},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(spi, max11205_spi_ids);
> +