Linux Device Drivers Development

Distinguishing channels

You may find yourself in trouble when there are multiple data channels per channel type. The dilemma would be how to identify them. There are two solutions for that: indexes and modifiers.

Using indexes: Given an ADC device with one channel line, indexing is not needed. Its channel definition would be:

static const struct iio_chan_spec adc_channels[] = { 
        { 
                .type = IIO_VOLTAGE, 
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 
        }, 
} 

The attribute name resulting from the preceding channel would be in_voltage_raw:

/sys/bus/iio/iio:deviceX/in_voltage_raw

Now, let's say the converter has four or even eight channels. How do we identify them? The solution is to use indexes. Setting the .indexed field to 1 will mangle the channel ...