On Fri, 22 Sep 2017 13:12:08 -0700
"Ismail H. Kose" [off-list ref] wrote:

This patch provides an iio device driver for DS4422/DS4424 chips that support
two/four channel 7-bit Sink/Source Current DAC.

Signed-off-by: Ismail H. Kose <redacted>
Signed-off-by: Ismail H. Kose <redacted>

A few minor comments inline.  This is coming together nicely.

Jonathan

Lose previous two lines and use the logic in the error path.

+
+fail:
+	mutex_unlock(&data->lock);
+	return ret;
+}
+
+static int ds4424_set_value(struct iio_dev *indio_dev,
+			     int val, struct iio_chan_spec const *chan)
+{
+	struct ds4424_data *data = iio_priv(indio_dev);
+	int ret;
+
+	mutex_lock(&data->lock);
+	ret = i2c_smbus_write_byte_data(data->client,
+			DS4424_DAC_ADDR(chan->channel), val);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);

A goto unlock: would be slightly cleaner.

+		return ret;
+	}
+
+	data->raw[chan->channel] = val;
+	mutex_unlock(&data->lock);
+
+	return 0;
+}
+
+static int ds4424_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	union ds4424_raw_data raw;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = ds4424_get_value(indio_dev, val, chan->channel);
+		if (ret < 0) {
+			pr_err("%s : ds4424_get_value returned %d\n",
+							__func__, ret);
+			return ret;
+		}
+		raw.bits = *val;
+		*val = raw.dx;
+		if (raw.source_bit == DS4424_SINK_I)
+			*val = -*val;
+		return IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ds4424_write_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int val, int val2, long mask)
+{
+	union ds4424_raw_data raw;
+
+	if (val2 != 0)
+		return -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		if (val < S8_MIN || val > S8_MAX)
+			return -EINVAL;
+
+		if (val > 0) {
+			raw.source_bit = DS4424_SOURCE_I;
+			raw.dx = val;
+		} else {
+			raw.source_bit = DS4424_SINK_I;
+			raw.dx = -val;
+		}
+
+		return ds4424_set_value(indio_dev, raw.bits, chan);
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int ds4424_verify_chip(struct iio_dev *indio_dev)
+{
+	int ret, val;
+
+	ret = ds4424_get_value(indio_dev, &val, DS4424_DAC_ADDR(0));
+	if (ret < 0)
+		dev_err(&indio_dev->dev,
+				"%s failed. ret: %d\n", __func__, ret);
+
+	return ret;
+}
+
+static int __maybe_unused ds4424_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct ds4424_data *data = iio_priv(indio_dev);
+	int ret = 0;
+	int i;
+
+	for (i = 0; i < indio_dev->num_channels; i++) {
+		data->save[i] = data->raw[i];
+		ret = ds4424_set_value(indio_dev, 0,
+				&indio_dev->channels[i]);
+		if (ret < 0)
+			return ret;
+	}
+	return ret;
+}
+
+static int __maybe_unused ds4424_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct ds4424_data *data = iio_priv(indio_dev);
+	int ret = 0;
+	int i;
+
+	for (i = 0; i < indio_dev->num_channels; i++) {
+		ret = ds4424_set_value(indio_dev, data->save[i],
+				&indio_dev->channels[i]);
+		if (ret < 0)
+			return ret;
+	}
+	return ret;
+}
+
+static SIMPLE_DEV_PM_OPS(ds4424_pm_ops, ds4424_suspend, ds4424_resume);
+
+static const struct iio_info ds4424_info = {
+	.read_raw = ds4424_read_raw,
+	.write_raw = ds4424_write_raw,
+};
+
+static int ds4424_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct ds4424_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev) {
+		dev_err(&client->dev, "iio dev alloc failed.\n");
+		return -ENOMEM;
+	}
+
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	indio_dev->name = id->name;
+	indio_dev->dev.of_node = client->dev.of_node;
+	indio_dev->dev.parent = &client->dev;
+
+	if (!client->dev.of_node) {
+		dev_err(&client->dev,
+				"Not found DT.\n");
+		return -EPERM;

Slightly odd error.  -ENODEV probably makes more sense...

+	}
+
+	data->vcc_reg = devm_regulator_get(&client->dev, "vcc");
+	if (IS_ERR(data->vcc_reg)) {
+		ret = PTR_ERR(data->vcc_reg);
+		dev_err(&client->dev,
+			"Failed to get vcc-supply regulator: %d\n", ret);
+		return ret;

return PTR_ERR(data->vcc_reg);

+	}
+
+	mutex_init(&data->lock);
+	ret = regulator_enable(data->vcc_reg);
+	if (ret < 0) {
+		dev_err(&client->dev,
+				"Unable to enable the regulator.\n");
+		return ret;
+	}
+
+	usleep_range(1000, 1200);
+	ret = ds4424_verify_chip(indio_dev);
+	if (ret < 0)

regulator disable?  Easier if you do a goto block at the end
for any error handling which is not a valid direct return
(see below).

+		return -ENXIO;
+
+	switch (id->driver_data) {
+	case ID_DS4422:
+		indio_dev->num_channels = DS4422_MAX_DAC_CHANNELS;
+		break;
+	case ID_DS4424:
+		indio_dev->num_channels = DS4424_MAX_DAC_CHANNELS;
+		break;
+	default:
+		dev_err(&client->dev,
+				"ds4424: Invalid chip id.\n");
+		regulator_disable(data->vcc_reg);

Given you have multiple error paths where regulator_disable is needed,
I would prefer this done as a goto with the error handling laid
out at the end of this function rather than mutiple copies inline.

+		return -ENXIO;
+	}
+
+	indio_dev->channels = ds4424_channels;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &ds4424_info;
+
+	ret = iio_device_register(indio_dev);
+	if (ret < 0) {
+		dev_err(&client->dev,
+				"iio_device_register failed. ret: %d\n", ret);
+		regulator_disable(data->vcc_reg);
+	}
+
+	return ret;
+}
+
+static int ds4424_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct ds4424_data *data = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	regulator_disable(data->vcc_reg);
+
+	return 0;
+}
+
+static const struct i2c_device_id ds4424_id[] = {
+	{ "ds4422", ID_DS4422 },
+	{ "ds4424", ID_DS4424 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, ds4424_id);
+
+static const struct of_device_id ds4424_of_match[] = {
+	{ .compatible = "maxim,ds4422" },
+	{ .compatible = "maxim,ds4424" },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, ds4424_of_match);
+
+static struct i2c_driver ds4424_driver = {
+	.driver = {
+		.name	= "ds4424",
+		.of_match_table = ds4424_of_match,
+		.pm     = &ds4424_pm_ops,
+	},
+	.probe		= ds4424_probe,
+	.remove		= ds4424_remove,
+	.id_table	= ds4424_id,
+};
+module_i2c_driver(ds4424_driver);
+
+MODULE_DESCRIPTION("Maxim DS4424 DAC Driver");
+MODULE_AUTHOR("Ismail H. Kose [off-list ref]");
+MODULE_AUTHOR("Vishal Sood [off-list ref]");
+MODULE_AUTHOR("David Jung [off-list ref]");
+MODULE_LICENSE("GPL v2");