staging:iio:Documentation in kernel pull description.
Very basic description of the way iio consumers work and how to use this functionality. Signed-off-by: Jonathan Cameron <jic23@kernel.org> Acked-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
e0f8a24e0e
commit
4eeb3335bb
|
@ -0,0 +1,58 @@
|
|||
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_st_read_channel_raw() - get a reading
|
||||
iio_st_read_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_st_channel_get_all.
|
||||
|
Loading…
Reference in New Issue