iio: adc: vf610_adc: add helper function to read samples

This is a precursor change to make it simpler to remove the 'mlock'
usage. Having the code in it's own helper function, also makes it easier
to read the error paths.
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Haibo Chen <haibo.chen@nxp.com>
Link: https://lore.kernel.org/r/20221004134909.1692021-10-nuno.sa@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/vf610_adc.c

@@ -622,6 +622,58 @@ static const struct attribute_group vf610_attribute_group = {
 	.attrs = vf610_attributes,
 };
 
+static int vf610_read_sample(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, int *val)
+{
+	struct vf610_adc *info = iio_priv(indio_dev);
+	unsigned int hc_cfg;
+	int ret;
+
+	mutex_lock(&indio_dev->mlock);
+	if (iio_buffer_enabled(indio_dev)) {
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	reinit_completion(&info->completion);
+	hc_cfg = VF610_ADC_ADCHC(chan->channel);
+	hc_cfg |= VF610_ADC_AIEN;
+	writel(hc_cfg, info->regs + VF610_REG_ADC_HC0);
+	ret = wait_for_completion_interruptible_timeout(&info->completion,
+							VF610_ADC_TIMEOUT);
+	if (ret == 0) {
+		ret = -ETIMEDOUT;
+		goto out_unlock;
+	}
+
+	if (ret < 0)
+		goto out_unlock;
+
+	switch (chan->type) {
+	case IIO_VOLTAGE:
+		*val = info->value;
+		break;
+	case IIO_TEMP:
+		/*
+		 * Calculate in degree Celsius times 1000
+		 * Using the typical sensor slope of 1.84 mV/°C
+		 * and VREFH_ADC at 3.3V, V at 25°C of 699 mV
+		 */
+		*val = 25000 - ((int)info->value - VF610_VTEMP25_3V3) *
+				1000000 / VF610_TEMP_SLOPE_COEFF;
+
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+out_unlock:
+	mutex_unlock(&indio_dev->mlock);
+
+	return ret;
+}
+
 static int vf610_read_raw(struct iio_dev *indio_dev,
 			struct iio_chan_spec const *chan,
 			int *val,
@@ -629,53 +681,15 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
 			long mask)
 {
 	struct vf610_adc *info = iio_priv(indio_dev);
-	unsigned int hc_cfg;
 	long ret;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 	case IIO_CHAN_INFO_PROCESSED:
-		mutex_lock(&indio_dev->mlock);
-		if (iio_buffer_enabled(indio_dev)) {
-			mutex_unlock(&indio_dev->mlock);
-			return -EBUSY;
-		}
-
-		reinit_completion(&info->completion);
-		hc_cfg = VF610_ADC_ADCHC(chan->channel);
-		hc_cfg |= VF610_ADC_AIEN;
-		writel(hc_cfg, info->regs + VF610_REG_ADC_HC0);
-		ret = wait_for_completion_interruptible_timeout
-				(&info->completion, VF610_ADC_TIMEOUT);
-		if (ret == 0) {
-			mutex_unlock(&indio_dev->mlock);
-			return -ETIMEDOUT;
-		}
-		if (ret < 0) {
-			mutex_unlock(&indio_dev->mlock);
+		ret = vf610_read_sample(indio_dev, chan, val);
+		if (ret < 0)
 			return ret;
-		}
-
-		switch (chan->type) {
-		case IIO_VOLTAGE:
-			*val = info->value;
-			break;
-		case IIO_TEMP:
-			/*
-			 * Calculate in degree Celsius times 1000
-			 * Using the typical sensor slope of 1.84 mV/°C
-			 * and VREFH_ADC at 3.3V, V at 25°C of 699 mV
-			 */
-			*val = 25000 - ((int)info->value - VF610_VTEMP25_3V3) *
-					1000000 / VF610_TEMP_SLOPE_COEFF;
-
-			break;
-		default:
-			mutex_unlock(&indio_dev->mlock);
-			return -EINVAL;
-		}
 
-		mutex_unlock(&indio_dev->mlock);
 		return IIO_VAL_INT;
 
 	case IIO_CHAN_INFO_SCALE: