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| -rw-r--r-- | drivers/staging/iio/Documentation/inkernel.txt | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/drivers/staging/iio/Documentation/inkernel.txt b/drivers/staging/iio/Documentation/inkernel.txt new file mode 100644 index 00000000000..a05823e955d --- /dev/null +++ b/drivers/staging/iio/Documentation/inkernel.txt @@ -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. + |