PID  PPID USER     STAT   VSZ %VSZ %CPU COMMAND
  144     2 root     DW       0   0%  33% [ina226:1-8800us]
  141     2 root     DW       0   0%  25% [ina226:0-8800us]
   40     2 root     SW       0   0%  15% [irq/156-4802a00]
  147     2 root     DW       0   0%   7% [ina226:2-8800us]
  145     1 root     S     1236   0%   6% dd if /dev/iio:device1 of /dev/null
  148     1 root     S     1236   0%   4% dd if /dev/iio:device2 of /dev/null
  149   137 root     R     1244   0%   3% top -d 1
  142     1 root     S     1236   0%   2% dd if /dev/iio:device0 of /dev/null
Signed-off-by: NMarc Titinger <mtitinger@baylibre.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Different probe modules use different resistor values. The front-end
application may read a probe ID (from eeprom) and set the shunt value
accordingly.
Signed-off-by: NMarc Titinger <mtitinger@baylibre.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

This can lead to repeated or skipped samples depending on the clock beat
between the capture thread and the chip sampling clock, but will also spare
reading/waiting for the Capture Ready Flag and improve the available i2c
bandwidth for reading measurements.

Output of iio_info:
...snip...
4 device-specific attributes found:
  attr 0: in_oversampling_ratio value: 4
  attr 1: in_allow_async_readout value: 0
  attr 2: integration_time_available value: 140 204 332 588 1100 2116...
  attr 3: in_sampling_frequency value: 114
Signed-off-by: NMarc Titinger <mtitinger@baylibre.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

in SOFTWARE buffer mode, a kthread will capture the active scan_elements
into a kfifo, then compute the remaining time until the next capture tick
and do an active wait (udelay).

This will produce a stream of up to fours channels plus a 64bits
timestamps (ns).

Tested with ina226, on BeagleBoneBlack.

Datasheet: http://www.ti.com/lit/gpn/ina226Signed-off-by: NMarc Titinger <mtitinger@baylibre.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>