iio: Add IIO support for the Measurement Computing CIO-DAC family

The Measurement Computing CIO-DAC is a family of 16-bit and 12-bit analog output devices. The analog outputs are from AD660BN/AD7237 converters with each output buffered by an OP-27. Voltage ranges are configured via physical jumpers on the device.

This driver does not support the devices' simulataneous update mode; the XFER jumper option should be deselected for all analog output channels.

This driver provides IIO support for the Measurement Computing CIO-DAC
family: CIO-DAC16, CIO-DAC08, and PC104-DAC06. The base port addresses for the devices may be configured via the base array module parameter.

Signed-off-by William Breathitt Gray <[email protected]>

---
Changes in v2:
- Change description from "DAC driver" to the more apt "IIO driver"
- Update message body to reflect 16-bit DAC resolution
- Change chan_out_states to hold ints in order to match val data type
- Verify val is within appropriate DAC value range before accepting

 MAINTAINERS               |   6 ++
 drivers/iio/dac/Kconfig   |   9 +++
 drivers/iio/dac/Makefile  |   1 +
 drivers/iio/dac/cio-dac.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 160 insertions(+)
 create mode 100644 drivers/iio/dac/cio-dac.c

MAINTAINERS +6 -0

index 345e757..b5c802d 100644
@@ -7318,6 +7318,12 @@ L:	[email protected]
 S:	Maintained
 F:	drivers/iio/potentiometer/mcp4531.c
 
+MEASUREMENT COMPUTING CIO-DAC IIO DRIVER
+M:	William Breathitt Gray <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	drivers/iio/dac/cio-dac.c
+
 MEDIA DRIVERS FOR RENESAS - VSP1
 M:	Laurent Pinchart <[email protected]>
 L:	[email protected]

drivers/iio/dac/Kconfig +9 -0

index ca81447..b9f0442 100644
@@ -181,6 +181,15 @@ config AD7303
 	  To compile this driver as module choose M here: the module will be called
 	  ad7303.
 
+config CIO_DAC
+	tristate "Measurement Computing CIO-DAC IIO driver"
+	depends on X86 && ISA_BUS_API
+	help
+	  Say yes here to build support for the Measurement Computing CIO-DAC
+	  analog output device family (CIO-DAC16, CIO-DAC08, PC104-DAC06). The
+	  base port addresses for the devices may be configured via the base
+	  array module parameter.
+
 config LPC18XX_DAC
 	tristate "NXP LPC18xx DAC driver"
 	depends on ARCH_LPC18XX || COMPILE_TEST

drivers/iio/dac/Makefile +1 -0

index 8b78d5c..b1a1206 100644
@@ -20,6 +20,7 @@ obj-$(CONFIG_AD5764) += ad5764.o
 obj-$(CONFIG_AD5791) += ad5791.o
 obj-$(CONFIG_AD5686) += ad5686.o
 obj-$(CONFIG_AD7303) += ad7303.o
+obj-$(CONFIG_CIO_DAC) += cio-dac.o
 obj-$(CONFIG_LPC18XX_DAC) += lpc18xx_dac.o
 obj-$(CONFIG_M62332) += m62332.o
 obj-$(CONFIG_MAX517) += max517.o

drivers/iio/dac/cio-dac.c new file +144 -0

new file mode 100644
index 0000000..5a743e2
@@ -0,0 +1,144 @@
+/*
+ * IIO driver for the Measurement Computing CIO-DAC
+ * Copyright (C) 2016 William Breathitt Gray
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * This driver supports the following Measurement Computing devices: CIO-DAC16,
+ * CIO-DAC06, and PC104-DAC06.
+ */
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/isa.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+#define CIO_DAC_NUM_CHAN 16
+
+#define CIO_DAC_CHAN(chan) {				\
+	.type = IIO_VOLTAGE,				\
+	.channel = chan,				\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
+	.indexed = 1,					\
+	.output = 1					\
+}
+
+#define CIO_DAC_EXTENT 32
+
+static unsigned int base[max_num_isa_dev(CIO_DAC_EXTENT)];
+static unsigned int num_cio_dac;
+module_param_array(base, uint, &num_cio_dac, 0);
+MODULE_PARM_DESC(base, "Measurement Computing CIO-DAC base addresses");
+
+/**
+ * struct cio_dac_iio - IIO device private data structure
+ * @chan_out_states:	channels' output states
+ * @base:		base port address of the IIO device
+ */
+struct cio_dac_iio {
+	int chan_out_states[CIO_DAC_NUM_CHAN];
+	unsigned int base;
+};
+
+static int cio_dac_read_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
+{
+	struct cio_dac_iio *const priv = iio_priv(indio_dev);
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	*val = priv->chan_out_states[chan->channel];
+
+	return IIO_VAL_INT;
+}
+
+static int cio_dac_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	struct cio_dac_iio *const priv = iio_priv(indio_dev);
+	const unsigned int chan_addr_offset = 2 * chan->channel;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	/* DAC can only accept up to a 16-bit value */
+	if ((unsigned int)val > 65535)
+		return -EINVAL;
+
+	priv->chan_out_states[chan->channel] = val;
+	outw(val, priv->base + chan_addr_offset);
+
+	return 0;
+}
+
+static const struct iio_info cio_dac_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = cio_dac_read_raw,
+	.write_raw = cio_dac_write_raw
+};
+
+static const struct iio_chan_spec cio_dac_channels[CIO_DAC_NUM_CHAN] = {
+	CIO_DAC_CHAN(0), CIO_DAC_CHAN(1), CIO_DAC_CHAN(2), CIO_DAC_CHAN(3),
+	CIO_DAC_CHAN(4), CIO_DAC_CHAN(5), CIO_DAC_CHAN(6), CIO_DAC_CHAN(7),
+	CIO_DAC_CHAN(8), CIO_DAC_CHAN(9), CIO_DAC_CHAN(10), CIO_DAC_CHAN(11),
+	CIO_DAC_CHAN(12), CIO_DAC_CHAN(13), CIO_DAC_CHAN(14), CIO_DAC_CHAN(15)
+};
+
+static int cio_dac_probe(struct device *dev, unsigned int id)
+{
+	struct iio_dev *indio_dev;
+	struct cio_dac_iio *priv;
+	unsigned int i;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	if (!devm_request_region(dev, base[id], CIO_DAC_EXTENT,
+		dev_name(dev))) {
+		dev_err(dev, "Unable to request port addresses (0x%X-0x%X)\n",
+			base[id], base[id] + CIO_DAC_EXTENT);
+		return -EBUSY;
+	}
+
+	indio_dev->info = &cio_dac_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = cio_dac_channels;
+	indio_dev->num_channels = CIO_DAC_NUM_CHAN;
+	indio_dev->name = dev_name(dev);
+
+	priv = iio_priv(indio_dev);
+	priv->base = base[id];
+
+	/* initialize DAC outputs to 0V */
+	for (i = 0; i < 32; i += 2)
+		outw(0, base[id] + i);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static struct isa_driver cio_dac_driver = {
+	.probe = cio_dac_probe,
+	.driver = {
+		.name = "cio-dac"
+	}
+};
+
+module_isa_driver(cio_dac_driver, num_cio_dac);
+
+MODULE_AUTHOR("William Breathitt Gray <[email protected]>");
+MODULE_DESCRIPTION("Measurement Computing CIO-DAC IIO driver");
+MODULE_LICENSE("GPL v2");