Backport essential fixes from 3.15

From Linux 3.10 on this driver required platform data to load, which makes it
unusable in OpenWRT. This commit backports the following fixes:
  * Move to regulator framework for scaling
  * Set endianness of the ADC to Big endian
  * Fix device-removal path
This commit should not be moved to newer kernel versions!

Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
---
diff -uprN a/drivers/staging/iio/adc/ad799x_core.c b/drivers/staging/iio/adc/ad799x_core.c
--- a/drivers/staging/iio/adc/ad799x_core.c
+++ b/drivers/staging/iio/adc/ad799x_core.c
@@ -163,7 +163,6 @@ static int ad799x_read_raw(struct iio_de
 {
 	int ret;
 	struct ad799x_state *st = iio_priv(indio_dev);
-	unsigned int scale_uv;
 
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
@@ -180,10 +179,12 @@ static int ad799x_read_raw(struct iio_de
 			RES_MASK(chan->scan_type.realbits);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
-		scale_uv = (st->int_vref_mv * 1000) >> chan->scan_type.realbits;
-		*val =  scale_uv / 1000;
-		*val2 = (scale_uv % 1000) * 1000;
-		return IIO_VAL_INT_PLUS_MICRO;
+		ret = regulator_get_voltage(st->vref);
+		if (ret < 0)
+			return ret;
+		*val =  ret / 1000;
+		*val2 = chan->scan_type.realbits;
+		return IIO_VAL_FRACTIONAL_LOG2;
 	}
 	return -EINVAL;
 }
@@ -474,7 +475,13 @@ static const struct iio_info ad7993_4_7_
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
 	.scan_index = (_index), \
-	.scan_type = IIO_ST('u', _realbits, 16, 12 - (_realbits)), \
+	.scan_type = { \
+		.sign = 'u', \
+		.realbits = (_realbits), \
+		.storagebits = 16, \
+		.shift = 12 - (_realbits), \
+		.endianness = IIO_BE, \
+		}, \
 	.event_mask = (_evmask), \
 }
 
@@ -584,7 +591,6 @@ static int ad799x_probe(struct i2c_clien
 				   const struct i2c_device_id *id)
 {
 	int ret;
-	struct ad799x_platform_data *pdata = client->dev.platform_data;
 	struct ad799x_state *st;
 	struct iio_dev *indio_dev = iio_device_alloc(sizeof(*st));
 
@@ -601,17 +607,21 @@ static int ad799x_probe(struct i2c_clien
 
 	/* TODO: Add pdata options for filtering and bit delay */
 
-	if (!pdata)
-		return -EINVAL;
-
-	st->int_vref_mv = pdata->vref_mv;
-
-	st->reg = regulator_get(&client->dev, "vcc");
-	if (!IS_ERR(st->reg)) {
-		ret = regulator_enable(st->reg);
-		if (ret)
-			goto error_put_reg;
+	st->reg = devm_regulator_get(&client->dev, "vcc");
+	if (IS_ERR(st->reg))
+		return PTR_ERR(st->reg);
+	ret = regulator_enable(st->reg);
+	if (ret)
+		return ret;
+	st->vref = devm_regulator_get(&client->dev, "vref");
+	if (IS_ERR(st->vref)) {
+		ret = PTR_ERR(st->vref);
+		goto error_disable_reg;
 	}
+	ret = regulator_enable(st->vref);
+	if (ret)
+		goto error_disable_reg;
+
 	st->client = client;
 
 	indio_dev->dev.parent = &client->dev;
@@ -624,7 +634,7 @@ static int ad799x_probe(struct i2c_clien
 
 	ret = ad799x_register_ring_funcs_and_init(indio_dev);
 	if (ret)
-		goto error_disable_reg;
+		goto error_disable_vref;
 
 	if (client->irq > 0) {
 		ret = request_threaded_irq(client->irq,
@@ -648,12 +658,10 @@ error_free_irq:
 		free_irq(client->irq, indio_dev);
 error_cleanup_ring:
 	ad799x_ring_cleanup(indio_dev);
+error_disable_vref:
+	regulator_disable(st->vref);
 error_disable_reg:
-	if (!IS_ERR(st->reg))
-		regulator_disable(st->reg);
-error_put_reg:
-	if (!IS_ERR(st->reg))
-		regulator_put(st->reg);
+	regulator_disable(st->reg);
 	iio_device_free(indio_dev);
 
 	return ret;
@@ -669,10 +677,8 @@ static int ad799x_remove(struct i2c_clie
 		free_irq(client->irq, indio_dev);
 
 	ad799x_ring_cleanup(indio_dev);
-	if (!IS_ERR(st->reg)) {
-		regulator_disable(st->reg);
-		regulator_put(st->reg);
-	}
+	regulator_disable(st->vref);
+	regulator_disable(st->reg);
 	kfree(st->rx_buf);
 	iio_device_free(indio_dev);
 
diff -uprN a/drivers/staging/iio/adc/ad799x.h b/drivers/staging/iio/adc/ad799x.h
--- a/drivers/staging/iio/adc/ad799x.h
+++ b/drivers/staging/iio/adc/ad799x.h
@@ -103,7 +103,7 @@ struct ad799x_state {
 	struct i2c_client		*client;
 	const struct ad799x_chip_info	*chip_info;
 	struct regulator		*reg;
-	u16				int_vref_mv;
+	struct regulator		*vref;
 	unsigned			id;
 	u16				config;
 
@@ -111,14 +111,6 @@ struct ad799x_state {
 	unsigned int			transfer_size;
 };
 
-/*
- * TODO: struct ad799x_platform_data needs to go into include/linux/iio
- */
-
-struct ad799x_platform_data {
-	u16				vref_mv;
-};
-
 #ifdef CONFIG_AD799X_RING_BUFFER
 int ad799x_register_ring_funcs_and_init(struct iio_dev *indio_dev);
 void ad799x_ring_cleanup(struct iio_dev *indio_dev);