iio: adc: vf610: let channel order can be specified in device tree

Add attribute 'use-channels' to specify which channel is used by ADC in device tree.

drivers/iio/adc/vf610_adc.c

@@ -537,7 +537,9 @@ static const struct iio_chan_spec_ext_info vf610_ext_info[] = {
 	},							\
 }
 
-static const struct iio_chan_spec vf610_adc_iio_channels[] = {
+#define MAX_IIO_CHANNEL_NUM 16
+
+static struct iio_chan_spec vf610_adc_iio_channels[] = {
 	VF610_ADC_CHAN(0, IIO_VOLTAGE),
 	VF610_ADC_CHAN(1, IIO_VOLTAGE),
 	VF610_ADC_CHAN(2, IIO_VOLTAGE),
@@ -819,6 +821,8 @@ static int vf610_adc_probe(struct platform_device *pdev)
 	struct resource *mem;
 	int irq;
 	int ret;
+	int i;
+	int use_channel[MAX_IIO_CHANNEL_NUM];
 	u32 channels;
 
 	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(struct vf610_adc));
@@ -883,6 +887,13 @@ static int vf610_adc_probe(struct platform_device *pdev)
 	if (ret)
 		channels = ARRAY_SIZE(vf610_adc_iio_channels);
 
+	if (!of_property_read_u32_array(pdev->dev.of_node, "use-channels", use_channel, (int)channels)) {
+		if (((int)channels) <= MAX_IIO_CHANNEL_NUM) {
+			for (i = 0; i < (int)channels; i++)
+				vf610_adc_iio_channels[i].channel = use_channel[i];
+		}
+	}
+
 	indio_dev->name = dev_name(&pdev->dev);
 	indio_dev->dev.parent = &pdev->dev;
 	indio_dev->dev.of_node = pdev->dev.of_node;