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- Industrial I/O Subsystem in kernel consumers.
- The IIO subsystem can act as a layer under other elements of the kernel
- providing a means of obtaining ADC type readings or of driving DAC type
- signals. The functionality supported will grow as use cases arise.
- Describing the channel mapping (iio/machine.h)
- Channel associations are described using:
- struct iio_map {
- const char *adc_channel_label;
- const char *consumer_dev_name;
- const char *consumer_channel;
- };
- adc_channel_label identifies the channel on the IIO device by being
- matched against the datasheet_name field of the iio_chan_spec.
- consumer_dev_name allows identification of the consumer device.
- This are then used to find the channel mapping from the consumer device (see
- below).
- Finally consumer_channel is a string identifying the channel to the consumer.
- (Perhaps 'battery_voltage' or similar).
- An array of these structures is then passed to the IIO driver.
- Supporting in kernel interfaces in the driver (driver.h)
- The driver must provide datasheet_name values for its channels and
- must pass the iio_map structures and a pointer to its own iio_dev structure
- on to the core via a call to iio_map_array_register. On removal,
- iio_map_array_unregister reverses this process.
- The result of this is that the IIO core now has all the information needed
- to associate a given channel with the consumer requesting it.
- Acting as an IIO consumer (consumer.h)
- The consumer first has to obtain an iio_channel structure from the core
- by calling iio_channel_get(). The correct channel is identified by:
- * matching dev or dev_name against consumer_dev and consumer_dev_name
- * matching consumer_channel against consumer_channel in the map
- There are then a number of functions that can be used to get information
- about this channel such as it's current reading.
- e.g.
- iio_read_channel_raw() - get a reading
- iio_get_channel_type() - get the type of channel
- There is also provision for retrieving all of the channels associated
- with a given consumer. This is useful for generic drivers such as
- iio_hwmon where the number and naming of channels is not known by the
- consumer driver. To do this, use iio_channel_get_all.
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