Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux

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>

authored by

Jonathan Cameron and committed by
Greg Kroah-Hartman
4eeb3335 e0f8a24e

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