Update documentation

diff --git a/comedi/drivers/ni_atmio.c b/comedi/drivers/ni_atmio.c
index 5770820a7ecb322abdd297dbc45ce03227040504..4d7d1d2d3b5703af05b10fa79eceaa0da2756203 100644 (file)
--- a/comedi/drivers/ni_atmio.c
+++ b/comedi/drivers/ni_atmio.c
@@ -39,6 +39,9 @@ boards seem to boot into a state where the all calibration DACs
 are at one extreme of their range, thus the default calibration
 is terrible.  Calibration at boot is strongly encouraged.
 
+To use the extended digital I/O on some of the boards, enable the
+8255 driver when configuring the Comedi source tree.
+
 External triggering is supported for some events.  The channel index
 (scan_begin_arg, etc.) maps to PFI0 - PFI9.