--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Industrial I/O driver for Microchip digital potentiometers
+ *
+ * Copyright (c) 2018 Chris Coffey <cmc@babblebit.net>
+ * Based on: Slawomir Stepien's code from mcp4131.c
+ *
+ * Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/11195c.pdf
+ *
+ * DEVID #Wipers #Positions Resistance (kOhm)
+ * mcp41010 1 256 10
+ * mcp41050 1 256 50
+ * mcp41100 1 256 100
+ * mcp42010 2 256 10
+ * mcp42050 2 256 50
+ * mcp42100 2 256 100
+ */
+
+#include <linux/cache.h>
+#include <linux/err.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+
+#define MCP41010_MAX_WIPERS 2
+#define MCP41010_WRITE BIT(4)
+#define MCP41010_WIPER_MAX 255
+#define MCP41010_WIPER_CHANNEL BIT(0)
+
+struct mcp41010_cfg {
+ char name[16];
+ int wipers;
+ int kohms;
+};
+
+enum mcp41010_type {
+ MCP41010,
+ MCP41050,
+ MCP41100,
+ MCP42010,
+ MCP42050,
+ MCP42100,
+};
+
+static const struct mcp41010_cfg mcp41010_cfg[] = {
+ [MCP41010] = { .name = "mcp41010", .wipers = 1, .kohms = 10, },
+ [MCP41050] = { .name = "mcp41050", .wipers = 1, .kohms = 50, },
+ [MCP41100] = { .name = "mcp41100", .wipers = 1, .kohms = 100, },
+ [MCP42010] = { .name = "mcp42010", .wipers = 2, .kohms = 10, },
+ [MCP42050] = { .name = "mcp42050", .wipers = 2, .kohms = 50, },
+ [MCP42100] = { .name = "mcp42100", .wipers = 2, .kohms = 100, },
+};
+
+struct mcp41010_data {
+ struct spi_device *spi;
+ const struct mcp41010_cfg *cfg;
+ struct mutex lock; /* Protect write sequences */
+ unsigned int value[MCP41010_MAX_WIPERS]; /* Cache wiper values */
+ u8 buf[2] ____cacheline_aligned;
+};
+
+#define MCP41010_CHANNEL(ch) { \
+ .type = IIO_RESISTANCE, \
+ .indexed = 1, \
+ .output = 1, \
+ .channel = (ch), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+static const struct iio_chan_spec mcp41010_channels[] = {
+ MCP41010_CHANNEL(0),
+ MCP41010_CHANNEL(1),
+};
+
+static int mcp41010_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct mcp41010_data *data = iio_priv(indio_dev);
+ int channel = chan->channel;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ *val = data->value[channel];
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ *val = 1000 * data->cfg->kohms;
+ *val2 = MCP41010_WIPER_MAX;
+ return IIO_VAL_FRACTIONAL;
+ }
+
+ return -EINVAL;
+}
+
+static int mcp41010_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ int err;
+ struct mcp41010_data *data = iio_priv(indio_dev);
+ int channel = chan->channel;
+
+ if (mask != IIO_CHAN_INFO_RAW)
+ return -EINVAL;
+
+ if (val > MCP41010_WIPER_MAX || val < 0)
+ return -EINVAL;
+
+ mutex_lock(&data->lock);
+
+ data->buf[0] = MCP41010_WIPER_CHANNEL << channel;
+ data->buf[0] |= MCP41010_WRITE;
+ data->buf[1] = val & 0xff;
+
+ err = spi_write(data->spi, data->buf, sizeof(data->buf));
+ if (!err)
+ data->value[channel] = val;
+
+ mutex_unlock(&data->lock);
+
+ return err;
+}
+
+static const struct iio_info mcp41010_info = {
+ .read_raw = mcp41010_read_raw,
+ .write_raw = mcp41010_write_raw,
+};
+
+static int mcp41010_probe(struct spi_device *spi)
+{
+ int err;
+ struct device *dev = &spi->dev;
+ struct mcp41010_data *data;
+ struct iio_dev *indio_dev;
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+ spi_set_drvdata(spi, indio_dev);
+ data->spi = spi;
+ data->cfg = of_device_get_match_data(&spi->dev);
+ if (!data->cfg)
+ data->cfg = &mcp41010_cfg[spi_get_device_id(spi)->driver_data];
+
+ mutex_init(&data->lock);
+
+ indio_dev->dev.parent = dev;
+ indio_dev->info = &mcp41010_info;
+ indio_dev->channels = mcp41010_channels;
+ indio_dev->num_channels = data->cfg->wipers;
+ indio_dev->name = data->cfg->name;
+
+ err = devm_iio_device_register(dev, indio_dev);
+ if (err)
+ dev_info(&spi->dev, "Unable to register %s\n", indio_dev->name);
+
+ return err;
+}
+
+static const struct of_device_id mcp41010_match[] = {
+ { .compatible = "microchip,mcp41010", .data = &mcp41010_cfg[MCP41010] },
+ { .compatible = "microchip,mcp41050", .data = &mcp41010_cfg[MCP41050] },
+ { .compatible = "microchip,mcp41100", .data = &mcp41010_cfg[MCP41100] },
+ { .compatible = "microchip,mcp42010", .data = &mcp41010_cfg[MCP42010] },
+ { .compatible = "microchip,mcp42050", .data = &mcp41010_cfg[MCP42050] },
+ { .compatible = "microchip,mcp42100", .data = &mcp41010_cfg[MCP42100] },
+ {}
+};
+MODULE_DEVICE_TABLE(of, mcp41010_match);
+
+static const struct spi_device_id mcp41010_id[] = {
+ { "mcp41010", MCP41010 },
+ { "mcp41050", MCP41050 },
+ { "mcp41100", MCP41100 },
+ { "mcp42010", MCP42010 },
+ { "mcp42050", MCP42050 },
+ { "mcp42100", MCP42100 },
+ {}
+};
+MODULE_DEVICE_TABLE(spi, mcp41010_id);
+
+static struct spi_driver mcp41010_driver = {
+ .driver = {
+ .name = "mcp41010",
+ .of_match_table = mcp41010_match,
+ },
+ .probe = mcp41010_probe,
+ .id_table = mcp41010_id,
+};
+
+module_spi_driver(mcp41010_driver);
+
+MODULE_AUTHOR("Chris Coffey <cmc@babblebit.net>");
+MODULE_DESCRIPTION("MCP41010 digital potentiometer");
+MODULE_LICENSE("GPL v2");
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