1Industrial I/O Subsystem in kernel consumers.
2
3The IIO subsystem can act as a layer under other elements of the kernel
4providing a means of obtaining ADC type readings or of driving DAC type
5signals.  The functionality supported will grow as use cases arise.
6
7Describing the channel mapping (iio/machine.h)
8
9Channel associations are described using:
10
11struct iio_map {
12	const char *adc_channel_label;
13	const char *consumer_dev_name;
14	const char *consumer_channel;
15};
16
17adc_channel_label identifies the channel on the IIO device by being
18matched against the datasheet_name field of the iio_chan_spec.
19
20consumer_dev_name allows identification of the consumer device.
21This are then used to find the channel mapping from the consumer device (see
22below).
23
24Finally consumer_channel is a string identifying the channel to the consumer.
25(Perhaps 'battery_voltage' or similar).
26
27An array of these structures is then passed to the IIO driver.
28
29Supporting in kernel interfaces in the driver (driver.h)
30
31The driver must provide datasheet_name values for its channels and
32must pass the iio_map structures and a pointer to its own iio_dev structure
33 on to the core via a call to iio_map_array_register.  On removal,
34iio_map_array_unregister reverses this process.
35
36The result of this is that the IIO core now has all the information needed
37to associate a given channel with the consumer requesting it.
38
39Acting as an IIO consumer (consumer.h)
40
41The consumer first has to obtain an iio_channel structure from the core
42by calling iio_channel_get().  The correct channel is identified by:
43
44* matching dev or dev_name against consumer_dev and consumer_dev_name
45* matching consumer_channel against consumer_channel in the map
46
47There are then a number of functions that can be used to get information
48about this channel such as it's current reading.
49
50e.g.
51iio_read_channel_raw() - get a reading
52iio_get_channel_type() - get the type of channel
53
54There is also provision for retrieving all of the channels associated
55with a given consumer.  This is useful for generic drivers such as
56iio_hwmon where the number and naming of channels is not known by the
57consumer driver.  To do this, use iio_channel_get_all.
58
59