I try to make the continues mode work for the embedded adc of the imx6ul. Single mode works perfectly according to my device tree configuration. I compiled libiio and tried to use the buffer mode which returns with the following error:
$ ./iio_readdev 2198000.adc
Unable to allocate buffer: Invalid argument
Then I tried to configure the buffer from the file system with the following commands
$ echo 1 > /sys/bus/iio/devices/iio\:device0/scan_elements/in_voltage0_en
$ echo 100 > /sys/bus/iio/devices/iio\:device0/buffer/length
$ echo 1 > /sys/bus/iio/devices/iio\:device0/buffer/enable-sh: echo: write error: Invalid argument
What I do know is that the adc peripheral (adc@02198000) and the kernel driver vf610-adc have buffer support. Additionally there is this document called IMX6LXRM Rev. 0, 12/2015 i.MX Linux® Reference Manual which claims that continues mode is not supported but that document is already very outdated.