staging: comedi: das08: clarify sign-magnitude conversion
For DAS08/JR/16 and DAS08/JR/AO-16 boards, the 16-bit analog input
readings are assumed to be in a sign-magnitude format and need
converting to the COMEDI unsigned sample format. The expressions to do
the conversion look a little messy. Use a local variable `magnitude` to
make it easier to follow.
Also, there seems to be some discrepancy between the manual for these
boards and the COMEDI code. The manual implies that 0 is full-scale
negative and 65535 is full-scale positive. However, the COMEDI code has
used the sign-magnitude conversion for these boards since these two
boards were initially supported by a patch from an external contributor
to the COMEDI project back in 2001. Assume the code is correct for now,
but add a comment to mention the discrepancy.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 file changed