iio: add mcp4725 I2C DAC driver

v5:
* fix warnings (Jonathan Cameron)

v4:
* remove unused indio_dev pointer in mcp4725_data (Jonathan Cameron)
* use u16 instead of unsigned short in mcp4725_data (Jonathan Cameron)
* #include mcp4725.h from linux/iio/dac/

v3:
* move from staging to drivers/iio
* switch to chan_spec
* dev_get_drvdata() -> dev_to_iio_dev()
* annotate probe() and remove() with __devinit and __devexit

v2 (based on comments from Jonathan Cameron and Lars-Peter Clausen):
* did NOT switch to chan_spec yet
* rebase to staging-next tree, update iio header locations
* dropped dac.h #include, not needed
* strict_strtol() -> kstrtol()
* call iio_device_unregister() in remove()
* everything in one patch

Signed-off-by: Peter Meerwald <[e-mail]>
Acked-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/iio/dac/Kconfig

···
 	  This driver can also be built as a module.  If so, the module
 	  will be called max517.
 
+config MCP4725
+	tristate "MCP4725 DAC driver"
+	depends on I2C
+	---help---
+	  Say Y here if you want to build a driver for the Microchip
+	  MCP 4725 12-bit digital-to-analog converter (DAC) with I2C
+	  interface.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called mcp4725.
+
 endmenu

drivers/iio/dac/Makefile

···
 obj-$(CONFIG_AD5791) += ad5791.o
 obj-$(CONFIG_AD5686) += ad5686.o
 obj-$(CONFIG_MAX517) += max517.o
+obj-$(CONFIG_MCP4725) += mcp4725.o

drivers/iio/dac/mcp4725.c

···
+/*
+ * mcp4725.c - Support for Microchip MCP4725
+ *
+ * Copyright (C) 2012 Peter Meerwald <[e-mail]>
+ *
+ * Based on max517 by Roland Stigge <[e-mail]>
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License.  See the file COPYING in the main
+ * directory of this archive for more details.
+ *
+ * driver for the Microchip I2C 12-bit digital-to-analog converter (DAC)
+ * (7-bit I2C slave address 0x60, the three LSBs can be configured in
+ * hardware)
+ *
+ * writing the DAC value to EEPROM is not supported
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#include <linux/iio/dac/mcp4725.h>
+
+#define MCP4725_DRV_NAME "mcp4725"
+
+struct mcp4725_data {
+	struct i2c_client *client;
+	u16 vref_mv;
+	u16 dac_value;
+};
+
+#ifdef CONFIG_PM_SLEEP
+static int mcp4725_suspend(struct device *dev)
+{
+	u8 outbuf[2];
+
+	outbuf[0] = 0x3 << 4; /* power-down bits, 500 kOhm resistor */
+	outbuf[1] = 0;
+
+	return i2c_master_send(to_i2c_client(dev), outbuf, 2);
+}
+
+static int mcp4725_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct mcp4725_data *data = iio_priv(indio_dev);
+	u8 outbuf[2];
+
+	/* restore previous DAC value */
+	outbuf[0] = (data->dac_value >> 8) & 0xf;
+	outbuf[1] = data->dac_value & 0xff;
+
+	return i2c_master_send(to_i2c_client(dev), outbuf, 2);
+}
+
+static SIMPLE_DEV_PM_OPS(mcp4725_pm_ops, mcp4725_suspend, mcp4725_resume);
+#define MCP4725_PM_OPS (&mcp4725_pm_ops)
+#else
+#define MCP4725_PM_OPS NULL
+#endif
+
+static const struct iio_chan_spec mcp4725_channel = {
+	.type		= IIO_VOLTAGE,
+	.indexed	= 1,
+	.output		= 1,
+	.channel	= 0,
+	.info_mask	= IIO_CHAN_INFO_RAW_SEPARATE_BIT |
+			  IIO_CHAN_INFO_SCALE_SHARED_BIT,
+	.scan_type	= IIO_ST('u', 12, 16, 0),
+};
+
+static int mcp4725_set_value(struct iio_dev *indio_dev, int val)
+{
+	struct mcp4725_data *data = iio_priv(indio_dev);
+	u8 outbuf[2];
+	int ret;
+
+	if (val >= (1 << 12) || val < 0)
+		return -EINVAL;
+
+	outbuf[0] = (val >> 8) & 0xf;
+	outbuf[1] = val & 0xff;
+
+	ret = i2c_master_send(data->client, outbuf, 2);
+	if (ret < 0)
+		return ret;
+	else if (ret != 2)
+		return -EIO;
+	else
+		return 0;
+}
+
+static int mcp4725_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct mcp4725_data *data = iio_priv(indio_dev);
+	unsigned long scale_uv;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*val = data->dac_value;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		scale_uv = (data->vref_mv * 1000) >> 12;
+		*val =  scale_uv / 1000000;
+		*val2 = scale_uv % 1000000;
+		return IIO_VAL_INT_PLUS_MICRO;
+	}
+	return -EINVAL;
+}
+
+static int mcp4725_write_raw(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan,
+			       int val, int val2, long mask)
+{
+	struct mcp4725_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = mcp4725_set_value(indio_dev, val);
+		data->dac_value = val;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static const struct iio_info mcp4725_info = {
+	.read_raw = mcp4725_read_raw,
+	.write_raw = mcp4725_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int __devinit mcp4725_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct mcp4725_data *data;
+	struct iio_dev *indio_dev;
+	struct mcp4725_platform_data *platform_data = client->dev.platform_data;
+	u8 inbuf[3];
+	int err;
+
+	if (!platform_data || !platform_data->vref_mv) {
+		dev_err(&client->dev, "invalid platform data");
+		err = -EINVAL;
+		goto exit;
+	}
+
+	indio_dev = iio_device_alloc(sizeof(*data));
+	if (indio_dev == NULL) {
+		err = -ENOMEM;
+		goto exit;
+	}
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->info = &mcp4725_info;
+	indio_dev->channels = &mcp4725_channel;
+	indio_dev->num_channels = 1;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	data->vref_mv = platform_data->vref_mv;
+
+	/* read current DAC value */
+	err = i2c_master_recv(client, inbuf, 3);
+	if (err < 0) {
+		dev_err(&client->dev, "failed to read DAC value");
+		goto exit_free_device;
+	}
+	data->dac_value = (inbuf[1] << 4) | (inbuf[2] >> 4);
+
+	err = iio_device_register(indio_dev);
+	if (err)
+		goto exit_free_device;
+
+	dev_info(&client->dev, "MCP4725 DAC registered\n");
+
+	return 0;
+
+exit_free_device:
+	iio_device_free(indio_dev);
+exit:
+	return err;
+}
+
+static int __devexit mcp4725_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+
+	iio_device_unregister(indio_dev);
+	iio_device_free(indio_dev);
+
+	return 0;
+}
+
+static const struct i2c_device_id mcp4725_id[] = {
+	{ "mcp4725", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mcp4725_id);
+
+static struct i2c_driver mcp4725_driver = {
+	.driver = {
+		.name	= MCP4725_DRV_NAME,
+		.pm	= MCP4725_PM_OPS,
+	},
+	.probe		= mcp4725_probe,
+	.remove		= __devexit_p(mcp4725_remove),
+	.id_table	= mcp4725_id,
+};
+module_i2c_driver(mcp4725_driver);
+
+MODULE_AUTHOR("Peter Meerwald <[e-mail]>");
+MODULE_DESCRIPTION("MCP4725 12-bit DAC");
+MODULE_LICENSE("GPL");

include/linux/iio/dac/mcp4725.h

···
+/*
+ * MCP4725 DAC driver
+ *
+ * Copyright (C) 2012 Peter Meerwald <[e-mail]>
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#ifndef IIO_DAC_MCP4725_H_
+#define IIO_DAC_MCP4725_H_
+
+struct mcp4725_platform_data {
+	u16 vref_mv;
+};
+
+#endif /* IIO_DAC_MCP4725_H_ */