one-bit-adc-dac: Add initial version of one bit ADC-DAC

This allows remote reading and writing of the GPIOs. This is useful in
application that run on another PC, at system level, where multiple iio
devices and GPIO devices are integrated together.

Signed-off-by: Cristian Pop <cristian.pop@analog.com>

drivers/iio/addac/Kconfig

@@ -17,4 +17,12 @@ config AD74413R
 	  To compile this driver as a module, choose M here: the
 	  module will be called ad74413r.
 
+config ONE_BIT_ADC_DAC
+	tristate "ONE_BIT_ADC_DAC driver"
+	help
+	  Say yes here to build support for ONE_BIT_ADC_DAC driver.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called one-bit-adc-dac.
+
 endmenu

drivers/iio/addac/Makefile

@@ -5,3 +5,4 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_AD74413R) += ad74413r.o
+obj-$(CONFIG_ONE_BIT_ADC_DAC) += one-bit-adc-dac.o

drivers/iio/addac/one-bit-adc-dac.c

@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+/*
+ * one-bit-adc-dac
+ *
+ * Copyright 2022 Analog Devices Inc.
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/iio/iio.h>
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+
+enum ch_direction {
+	CH_IN,
+	CH_OUT,
+};
+
+struct one_bit_adc_dac_state {
+	int			in_num_ch;
+	int			out_num_ch;
+	struct platform_device  *pdev;
+	struct gpio_descs       *in_gpio_descs;
+	struct gpio_descs       *out_gpio_descs;
+	const char		**labels;
+};
+
+static int one_bit_adc_dac_read_raw(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan, int *val, int *val2, long info)
+{
+	struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
+	struct gpio_descs *descs;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		if (chan->output)
+			descs = st->out_gpio_descs;
+		else
+			descs = st->in_gpio_descs;
+		*val = gpiod_get_value_cansleep(descs->desc[chan->channel]);
+
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int one_bit_adc_dac_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val,
+			    int val2,
+			    long info)
+{
+	struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
+	int channel = chan->channel;
+
+	if (!chan->output)
+		return 0;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		gpiod_set_value_cansleep(st->out_gpio_descs->desc[channel], val);
+
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int one_bit_adc_dac_read_label(struct iio_dev *indio_dev,
+	const struct iio_chan_spec *chan, char *label)
+{
+	struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
+	int ch;
+
+	if (chan->output)
+		ch = chan->channel + st->in_num_ch;
+	else
+		ch = chan->channel;
+
+	return sprintf(label, "%s\n", st->labels[ch]);
+}
+
+static const struct iio_info one_bit_adc_dac_info = {
+	.read_raw = &one_bit_adc_dac_read_raw,
+	.write_raw = &one_bit_adc_dac_write_raw,
+	.read_label = &one_bit_adc_dac_read_label,
+};
+
+static int one_bit_adc_dac_set_ch(struct iio_chan_spec *channels,
+					int num_ch,
+					enum ch_direction direction)
+{
+	int i;
+
+	for (i = 0; i < num_ch; i++) {
+		channels[i].type = IIO_VOLTAGE;
+		channels[i].indexed = 1;
+		channels[i].channel = i;
+		channels[i].info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
+		channels[i].output = direction;
+	}
+
+	return 0;
+}
+
+static int one_bit_adc_dac_set_channel_label(struct iio_dev *indio_dev,
+						struct iio_chan_spec *channels,
+						int num_channels)
+{
+	struct device *device = indio_dev->dev.parent;
+	struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
+	struct fwnode_handle *fwnode;
+	struct fwnode_handle *child;
+	struct iio_chan_spec *chan;
+	const char *label;
+	int crt_ch = 0, child_num, i = 0;
+
+	fwnode = dev_fwnode(device);
+	child_num = device_get_child_node_count(device);
+
+	st->labels = devm_kzalloc(device, sizeof(*st->labels) * child_num, GFP_KERNEL);
+	if (!st->labels)
+		return -ENOMEM;
+
+	i = child_num;
+	fwnode_for_each_child_node(fwnode, child) {
+		if (fwnode_property_read_u32(child, "reg", &crt_ch))
+			continue;
+
+		if (crt_ch >= num_channels)
+			continue;
+
+		if (fwnode_property_read_string(child, "label", &label))
+			continue;
+
+		chan = &channels[crt_ch];
+		st->labels[--i] = label;
+	}
+
+	return 0;
+}
+
+static int one_bit_adc_dac_parse_dt(struct iio_dev *indio_dev)
+{
+	struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
+	struct iio_chan_spec *channels;
+	int ret, in_num_ch = 0, out_num_ch = 0;
+
+	st->in_gpio_descs = devm_gpiod_get_array_optional(&st->pdev->dev, "in", GPIOD_IN);
+	if (IS_ERR(st->in_gpio_descs))
+		return PTR_ERR(st->in_gpio_descs);
+
+	if (st->in_gpio_descs)
+		in_num_ch = st->in_gpio_descs->ndescs;
+
+	st->out_gpio_descs = devm_gpiod_get_array_optional(&st->pdev->dev, "out", GPIOD_OUT_LOW);
+	if (IS_ERR(st->out_gpio_descs))
+		return PTR_ERR(st->out_gpio_descs);
+
+	if (st->out_gpio_descs)
+		out_num_ch = st->out_gpio_descs->ndescs;
+	st->in_num_ch = in_num_ch;
+	st->out_num_ch = out_num_ch;
+
+	channels = devm_kcalloc(indio_dev->dev.parent, in_num_ch + out_num_ch,
+				sizeof(*channels), GFP_KERNEL);
+	if (!channels)
+		return -ENOMEM;
+
+	ret = one_bit_adc_dac_set_ch(&channels[0], in_num_ch, CH_IN);
+	if (ret)
+		return ret;
+
+	ret = one_bit_adc_dac_set_ch(&channels[in_num_ch], out_num_ch, CH_OUT);
+	if (ret)
+		return ret;
+
+	ret = one_bit_adc_dac_set_channel_label(indio_dev, channels, in_num_ch + out_num_ch);
+	if (ret)
+		return ret;
+
+	indio_dev->channels = channels;
+	indio_dev->num_channels = in_num_ch + out_num_ch;
+
+	return 0;
+}
+
+static int one_bit_adc_dac_probe(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev;
+	struct one_bit_adc_dac_state *st;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+	st->pdev = pdev;
+	indio_dev->name = "one-bit-adc-dac";
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &one_bit_adc_dac_info;
+
+	ret = one_bit_adc_dac_parse_dt(indio_dev);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(indio_dev->dev.parent, indio_dev);
+}
+
+static const struct of_device_id one_bit_adc_dac_dt_match[] = {
+	{ .compatible = "one-bit-adc-dac" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, one_bit_adc_dac_dt_match);
+
+static struct platform_driver one_bit_adc_dac_driver = {
+	.driver = {
+		.name = "one-bit-adc-dac",
+		.of_match_table = one_bit_adc_dac_dt_match,
+	},
+	.probe = one_bit_adc_dac_probe,
+};
+module_platform_driver(one_bit_adc_dac_driver);
+
+MODULE_AUTHOR("Cristian Pop <cristian.pop@analog.com>");
+MODULE_DESCRIPTION("One bit ADC DAC converter");
+MODULE_LICENSE("Dual BSD/GPL");