iio: potentiometer: add a driver for Maxim 5432-5435

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

Datasheet:
https://datasheets.maximintegrated.com/en/ds/MAX5432-MAX5435.pdf

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index ebc7c72..4cac017 100644 (file)
--- 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 8ff5513..091adf3 100644 (file)
--- 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 (file)
index 0000000..641b182
--- /dev/null
+++ b/drivers/iio/potentiometer/max5432.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Maxim Integrated MAX5432-MAX5435 digital potentiometer driver
+ * Copyright (C) 2019 Martin Kaiser <martin@kaiser.cx>
+ *
+ * Datasheet:
+ * https://datasheets.maximintegrated.com/en/ds/MAX5432-MAX5435.pdf
+ */
+
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/limits.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 MAX5432_OHM_50K   (50  * 1000)
+#define MAX5432_OHM_100K  (100 * 1000)
+
+/* Update the volatile (currently active) setting. */
+#define MAX5432_CMD_VREG  0x11
+
+struct max5432_data {
+       struct i2c_client *client;
+       unsigned long ohm;
+};
+
+static const struct iio_chan_spec max5432_channels[] = {
+       {
+               .type = IIO_RESISTANCE,
+               .indexed = 1,
+               .output = 1,
+               .channel = 0,
+               .address = MAX5432_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;
+
+       if (unlikely(data->ohm > INT_MAX))
+               return -ERANGE;
+
+       *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 = (unsigned long)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 *)MAX5432_OHM_50K  },
+       { .compatible = "maxim,max5433", .data = (void *)MAX5432_OHM_100K },
+       { .compatible = "maxim,max5434", .data = (void *)MAX5432_OHM_50K  },
+       { .compatible = "maxim,max5435", .data = (void *)MAX5432_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@kaiser.cx>");
+MODULE_DESCRIPTION("max5432-max5435 digital potentiometers");
+MODULE_LICENSE("GPL v2");