[RFC v2 08/11] iio: adc: sd modulator: add scale and offset support

[Olivier Moysan <olivier.moysan@foss.st.com>]

Register the SD modulator as an IIO backend device instead of
a standard IIO device. Expose scale and offset information to
IIO backend consumer.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 drivers/iio/adc/sd_adc_modulator.c | 106 +++++++++++++++++++++++------
 1 file changed, 86 insertions(+), 20 deletions(-)

diff --git a/drivers/iio/adc/sd_adc_modulator.c b/drivers/iio/adc/sd_adc_modulator.c
index 327cc2097f6c..e77e7884c403 100644
--- a/drivers/iio/adc/sd_adc_modulator.c
+++ b/drivers/iio/adc/sd_adc_modulator.c
@@ -6,44 +6,110 @@
  * Author: Arnaud Pouliquen <arnaud.pouliquen@st.com>.
  */
 
+#include <linux/iio/backend.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/triggered_buffer.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
 
-static const struct iio_info iio_sd_mod_iio_info;
+struct iio_sd_mod_priv {
+	struct regulator *vref;
+	int vref_mv;
+};
 
-static const struct iio_chan_spec iio_sd_mod_ch = {
-	.type = IIO_VOLTAGE,
-	.indexed = 1,
-	.scan_type = {
-		.sign = 'u',
-		.realbits = 1,
-		.shift = 0,
-	},
+static int sd_mod_enable(struct iio_backend *backend)
+{
+	struct iio_sd_mod_priv *priv = backend->priv;
+	int ret;
+
+	ret = regulator_enable(priv->vref);
+	if (ret) {
+		dev_err(&backend->dev, "Failed to enable regulator: %d\n", ret);
+		return ret;
+	}
+
+	ret = regulator_get_voltage(priv->vref);
+	priv->vref_mv = ret / 1000;
+
+	return 0;
+};
+
+static int sd_mod_disable(struct iio_backend *backend)
+{
+	struct iio_sd_mod_priv *priv = backend->priv;
+
+	return regulator_disable(priv->vref);
+};
+
+static int sd_mod_read(struct iio_backend *backend, int *val, int *val2, long mask)
+{
+	struct iio_sd_mod_priv *priv = backend->priv;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		*val = priv->vref_mv;
+		*val2 = 0;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_OFFSET:
+		*val = 0;
+		*val2 = 0;
+		return IIO_VAL_INT;
+	}
+
+	return -EINVAL;
+};
+
+static const struct iio_backend_ops sd_mod_ops = {
+	.enable = sd_mod_enable,
+	.disable = sd_mod_disable,
+	.read_raw = sd_mod_read,
 };
 
 static int iio_sd_mod_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
-	struct iio_dev *iio;
+	struct regulator *vref;
+	struct iio_backend *backend;
+	struct iio_sd_mod_priv *priv;
+	int ret;
 
-	iio = devm_iio_device_alloc(dev, 0);
-	if (!iio)
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
 		return -ENOMEM;
 
-	iio->name = dev_name(dev);
-	iio->info = &iio_sd_mod_iio_info;
-	iio->modes = INDIO_BUFFER_HARDWARE;
+	vref = devm_regulator_get_optional(dev, "vref");
+	if (IS_ERR(vref)) {
+		if (PTR_ERR(vref) != -ENODEV)
+			return dev_err_probe(dev, PTR_ERR(vref), "Failed to get vref\n");
+	} else {
+		priv->vref = vref;
+	}
 
-	iio->num_channels = 1;
-	iio->channels = &iio_sd_mod_ch;
+	backend = iio_backend_alloc(dev);
+	if (!backend) {
+		dev_err(dev, "Failed to allocate sd modulator backend data\n");
+		return -ENOMEM;
+	}
+
+	backend->priv = priv;
+	backend->ops = &sd_mod_ops;
+
+	ret = iio_backend_register(backend);
+	if (ret) {
+		dev_err(dev, "Failed to register backend: %d\n", ret);
+		goto err_free_backend;
+	}
 
-	platform_set_drvdata(pdev, iio);
+	return 0;
 
-	return devm_iio_device_register(&pdev->dev, iio);
-}
+err_free_backend:
+	iio_backend_free(&backend->dev);
+
+	return ret;
+};
 
 static const struct of_device_id sd_adc_of_match[] = {
 	{ .compatible = "sd-modulator" },
-- 
2.25.1