sysfs-bus-iio-dfsdm-adc-stm32

 1What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_spi_clk_freq
 2KernelVersion:	4.14
 3Contact:	arnaud.pouliquen@st.com
 4Description:
 5		For audio purpose only.
 6
 7		Used by audio driver to set/get the spi input frequency.
 8
 9		This is mandatory if DFSDM is slave on SPI bus, to
10		provide information on the SPI clock frequency during runtime
11		Notice that the SPI frequency should be a multiple of sample
12		frequency to ensure the precision.
13
14		if DFSDM input is SPI master:
15
16			Reading  SPI clkout frequency,
17			error on writing
18
19		If DFSDM input is SPI Slave:
20
21			Reading returns value previously set.
22			Writing value before starting conversions.