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Date: Sun, 21 Jul 2019 22:48:03 +0200 (CEST)
From: Peter Meerwald-Stadler <pmeerw@...erw.net>
To: Martin Kaiser <martin@...ser.cx>
cc: Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: potentiometer: add a driver for Maxim 5432-5435
On Sun, 21 Jul 2019, Martin Kaiser wrote:
> Add a driver for the Maxim Integrated MAX5432-MAX5435 family of digital
> potentiometers.
>
> These potentiometers are connected via I2C and have 32 wiper positions.
>
> Supported functionality
> - set the volatile wiper position
> - read the potentiometer scale
please see some minor comment below
> Datasheet:
> https://datasheets.maximintegrated.com/en/ds/MAX5432-MAX5435.pdf
>
> Signed-off-by: Martin Kaiser <martin@...ser.cx>
> ---
> .../bindings/iio/potentiometer/max5432.txt | 22 ++++
> drivers/iio/potentiometer/Kconfig | 11 ++
> drivers/iio/potentiometer/Makefile | 1 +
> drivers/iio/potentiometer/max5432.c | 131 +++++++++++++++++++++
> 4 files changed, 165 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/iio/potentiometer/max5432.txt
> create mode 100644 drivers/iio/potentiometer/max5432.c
>
> diff --git a/Documentation/devicetree/bindings/iio/potentiometer/max5432.txt b/Documentation/devicetree/bindings/iio/potentiometer/max5432.txt
> new file mode 100644
> index 000000000000..89ccc8fc7df1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/potentiometer/max5432.txt
> @@ -0,0 +1,22 @@
> +* Maxim Integrated MAX5432-MAX5435 Digital Potentiometers.
> +
> +The node for this driver must be a child node of an I2C controller, hence
> +all mandatory properties for your controller must be specified. See directory:
> +
> + Documentation/devicetree/bindings/i2c
> +
> +for more details.
> +
> +Required properties:
> + - compatible: Must be one of the following, depending on the
> + model:
> + "maxim,max5432"
> + "maxim,max5433"
> + "maxim,max5434"
> + "maxim,max5435"
> +
> +Example:
> +max5434@28 {
> + compatible = "maxim,max5434";
> + reg = <0x28>;
> +};
> diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
> index ebc7c72a5e36..4cac0173db8b 100644
> --- a/drivers/iio/potentiometer/Kconfig
> +++ b/drivers/iio/potentiometer/Kconfig
> @@ -26,6 +26,17 @@ config DS1803
> To compile this driver as a module, choose M here: the
> module will be called ds1803.
>
> +config MAX5432
> + tristate "Maxim MAX5432-MAX5435 Digital Potentiometer driver"
> + depends on I2C
> + help
> + Say yes here to build support for the Maxim
> + MAX5432, MAX5433, MAX5434 and MAX5435 digital
> + potentiometer chips.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called max5432.
> +
> config MAX5481
> tristate "Maxim MAX5481-MAX5484 Digital Potentiometer driver"
> depends on SPI
> diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
> index 8ff55138cf12..091adf3cdd0b 100644
> --- a/drivers/iio/potentiometer/Makefile
> +++ b/drivers/iio/potentiometer/Makefile
> @@ -6,6 +6,7 @@
> # When adding new entries keep the list in alphabetical order
> obj-$(CONFIG_AD5272) += ad5272.o
> obj-$(CONFIG_DS1803) += ds1803.o
> +obj-$(CONFIG_MAX5432) += max5432.o
> obj-$(CONFIG_MAX5481) += max5481.o
> obj-$(CONFIG_MAX5487) += max5487.o
> obj-$(CONFIG_MCP4018) += mcp4018.o
> diff --git a/drivers/iio/potentiometer/max5432.c b/drivers/iio/potentiometer/max5432.c
> new file mode 100644
> index 000000000000..959883297fb5
> --- /dev/null
> +++ b/drivers/iio/potentiometer/max5432.c
> @@ -0,0 +1,131 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Maxim Integrated MAX5432-MAX5435 digital potentiometer driver
> + * Copyright (C) 2019 Martin Kaiser <martin@...ser.cx>
> + *
> + * Datasheet:
> + * https://datasheets.maximintegrated.com/en/ds/MAX5432-MAX5435.pdf
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +
> +/* All chip variants have 32 wiper positions. */
> +#define MAX5432_MAX_POS 31
> +
> +#define OHM_50K (50 * 1000)
> +#define OHM_100K (100 * 1000)
MAX5432_ prefix please
> +
> +/* Update the volatile (currently active) setting. */
> +#define CMD_VREG 0x11
MAX5432_ prefix please
> +
> +struct max5432_data {
> + struct i2c_client *client;
> + u32 ohm;
> +};
> +
> +static const struct iio_chan_spec max5432_channels[] = {
> + {
> + .type = IIO_RESISTANCE,
> + .indexed = 1,
> + .output = 1,
> + .channel = 0,
> + .address = CMD_VREG,
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> + }
> +};
> +
> +static int max5432_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct max5432_data *data = iio_priv(indio_dev);
> +
> + if (mask != IIO_CHAN_INFO_SCALE)
> + return -EINVAL;
> +
> + *val = data->ohm;
> + *val2 = MAX5432_MAX_POS;
> +
> + return IIO_VAL_FRACTIONAL;
> +}
> +
> +static int max5432_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int val, int val2, long mask)
> +{
> + struct max5432_data *data = iio_priv(indio_dev);
> + u8 data_byte;
> +
> + if (mask != IIO_CHAN_INFO_RAW)
> + return -EINVAL;
> +
> + if (val < 0 || val > MAX5432_MAX_POS)
> + return -EINVAL;
> +
> + if (val2 != 0)
> + return -EINVAL;
> +
> + /* Wiper position is in bits D7-D3. (D2-D0 are don't care bits.) */
> + data_byte = val << 3;
> + return i2c_smbus_write_byte_data(
> + data->client, chan->address, data_byte);
> +}
> +
> +static const struct iio_info max5432_info = {
> + .read_raw = max5432_read_raw,
> + .write_raw = max5432_write_raw,
> +};
> +
> +static int max5432_probe(
> + struct i2c_client *client, const struct i2c_device_id *id)
> +{
> + struct device *dev = &client->dev;
> + struct iio_dev *indio_dev;
> + struct max5432_data *data;
> +
> + indio_dev = devm_iio_device_alloc(dev, sizeof(struct max5432_data));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + i2c_set_clientdata(client, indio_dev);
> +
> + data = iio_priv(indio_dev);
> + data->client = client;
> + data->ohm = (u32)of_device_get_match_data(dev);
> +
> + indio_dev->dev.parent = dev;
> + indio_dev->info = &max5432_info;
> + indio_dev->channels = max5432_channels;
> + indio_dev->num_channels = ARRAY_SIZE(max5432_channels);
> + indio_dev->name = client->name;
> +
> + return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +static const struct of_device_id max5432_dt_ids[] = {
> + { .compatible = "maxim,max5432", .data = (void *)OHM_50K },
> + { .compatible = "maxim,max5433", .data = (void *)OHM_100K },
> + { .compatible = "maxim,max5434", .data = (void *)OHM_50K },
> + { .compatible = "maxim,max5435", .data = (void *)OHM_100K },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, max5432_dt_ids);
> +
> +static struct i2c_driver max5432_driver = {
> + .driver = {
> + .name = "max5432",
> + .of_match_table = of_match_ptr(max5432_dt_ids),
> + },
> + .probe = max5432_probe,
> +};
> +
> +module_i2c_driver(max5432_driver);
> +
> +MODULE_AUTHOR("Martin Kaiser <martin@...ser.cx>");
> +MODULE_DESCRIPTION("max5432-max5435 digital potentiometers");
> +MODULE_LICENSE("GPL v2");
>
--
Peter Meerwald-Stadler
Mobile: +43 664 24 44 418
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