--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Industrial I/O driver for Microchip digital potentiometers
+ * Copyright (c) 2018 Axentia Technologies AB
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * Datasheet: http://www.microchip.com/downloads/en/DeviceDoc/22147a.pdf
+ *
+ * DEVID #Wipers #Positions Resistor Opts (kOhm)
+ * mcp4017 1 128 5, 10, 50, 100
+ * mcp4018 1 128 5, 10, 50, 100
+ * mcp4019 1 128 5, 10, 50, 100
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+
+#define MCP4018_WIPER_MAX 127
+
+struct mcp4018_cfg {
+ int kohms;
+};
+
+enum mcp4018_type {
+ MCP4018_502,
+ MCP4018_103,
+ MCP4018_503,
+ MCP4018_104,
+};
+
+static const struct mcp4018_cfg mcp4018_cfg[] = {
+ [MCP4018_502] = { .kohms = 5, },
+ [MCP4018_103] = { .kohms = 10, },
+ [MCP4018_503] = { .kohms = 50, },
+ [MCP4018_104] = { .kohms = 100, },
+};
+
+struct mcp4018_data {
+ struct i2c_client *client;
+ const struct mcp4018_cfg *cfg;
+};
+
+static const struct iio_chan_spec mcp4018_channel = {
+ .type = IIO_RESISTANCE,
+ .indexed = 1,
+ .output = 1,
+ .channel = 0,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+};
+
+static int mcp4018_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct mcp4018_data *data = iio_priv(indio_dev);
+ s32 ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ ret = i2c_smbus_read_byte(data->client);
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = 1000 * data->cfg->kohms;
+ *val2 = MCP4018_WIPER_MAX;
+ return IIO_VAL_FRACTIONAL;
+ }
+
+ return -EINVAL;
+}
+
+static int mcp4018_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct mcp4018_data *data = iio_priv(indio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ if (val > MCP4018_WIPER_MAX || val < 0)
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return i2c_smbus_write_byte(data->client, val);
+}
+
+static const struct iio_info mcp4018_info = {
+ .read_raw = mcp4018_read_raw,
+ .write_raw = mcp4018_write_raw,
+};
+
+#ifdef CONFIG_OF
+
+#define MCP4018_COMPATIBLE(of_compatible, cfg) { \
+ .compatible = of_compatible, \
+ .data = &mcp4018_cfg[cfg], \
+}
+
+static const struct of_device_id mcp4018_of_match[] = {
+ MCP4018_COMPATIBLE("microchip,mcp4017-502", MCP4018_502),
+ MCP4018_COMPATIBLE("microchip,mcp4017-103", MCP4018_103),
+ MCP4018_COMPATIBLE("microchip,mcp4017-503", MCP4018_503),
+ MCP4018_COMPATIBLE("microchip,mcp4017-104", MCP4018_104),
+ MCP4018_COMPATIBLE("microchip,mcp4018-502", MCP4018_502),
+ MCP4018_COMPATIBLE("microchip,mcp4018-103", MCP4018_103),
+ MCP4018_COMPATIBLE("microchip,mcp4018-503", MCP4018_503),
+ MCP4018_COMPATIBLE("microchip,mcp4018-104", MCP4018_104),
+ MCP4018_COMPATIBLE("microchip,mcp4019-502", MCP4018_502),
+ MCP4018_COMPATIBLE("microchip,mcp4019-103", MCP4018_103),
+ MCP4018_COMPATIBLE("microchip,mcp4019-503", MCP4018_503),
+ MCP4018_COMPATIBLE("microchip,mcp4019-104", MCP4018_104),
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mcp4018_of_match);
+
+#endif
+
+static int mcp4018_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct device *dev = &client->dev;
+ struct mcp4018_data *data;
+ struct iio_dev *indio_dev;
+ const struct of_device_id *match;
+
+ if (!i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_BYTE)) {
+ dev_err(dev, "SMBUS Byte transfers not supported\n");
+ return -EOPNOTSUPP;
+ }
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+ data = iio_priv(indio_dev);
+ i2c_set_clientdata(client, indio_dev);
+ data->client = client;
+
+ match = of_match_device(of_match_ptr(mcp4018_of_match), dev);
+ if (match)
+ data->cfg = of_device_get_match_data(dev);
+ else
+ data->cfg = &mcp4018_cfg[id->driver_data];
+
+ indio_dev->dev.parent = dev;
+ indio_dev->info = &mcp4018_info;
+ indio_dev->channels = &mcp4018_channel;
+ indio_dev->num_channels = 1;
+ indio_dev->name = client->name;
+
+ return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct i2c_device_id mcp4018_id[] = {
+ { "mcp4017-502", MCP4018_502 },
+ { "mcp4017-103", MCP4018_103 },
+ { "mcp4017-503", MCP4018_503 },
+ { "mcp4017-104", MCP4018_104 },
+ { "mcp4018-502", MCP4018_502 },
+ { "mcp4018-103", MCP4018_103 },
+ { "mcp4018-503", MCP4018_503 },
+ { "mcp4018-104", MCP4018_104 },
+ { "mcp4019-502", MCP4018_502 },
+ { "mcp4019-103", MCP4018_103 },
+ { "mcp4019-503", MCP4018_503 },
+ { "mcp4019-104", MCP4018_104 },
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, mcp4018_id);
+
+static struct i2c_driver mcp4018_driver = {
+ .driver = {
+ .name = "mcp4018",
+ .of_match_table = of_match_ptr(mcp4018_of_match),
+ },
+ .probe = mcp4018_probe,
+ .id_table = mcp4018_id,
+};
+
+module_i2c_driver(mcp4018_driver);
+
+MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
+MODULE_DESCRIPTION("MCP4018 digital potentiometer");
+MODULE_LICENSE("GPL");
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