staging: comedi: comedi_test: allow read-back of AO channels

COMEDI drivers often allow the last value written to a channel on an
analog output subdevice to be read back via the "insn_read" handler.
The "comedi_test" driver does not currently support that.  It is a bit
special because it loops back the last values written to the channel on
the analog output subdevice to be read back via corresponding channels
on the analog input subdevice.  The "insn_read" handler for the analog
input subdevice is `waveform_ai_insn_read()`.  Set that as the
"insn_read" handler for the analog output subdevice as well.

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>

diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c
index a750f84529ff638bd64f203f43acd00ca6504f23..468847a5da009641f0b81d0b16d1f6ef965fab53 100644 (file)
--- a/drivers/staging/comedi/drivers/comedi_test.c
+++ b/drivers/staging/comedi/drivers/comedi_test.c
@@ -457,6 +457,7 @@ static int waveform_attach(struct comedi_device *dev,
        s->maxdata = 0xffff;
        s->range_table = &waveform_ai_ranges;
        s->insn_write = waveform_ao_insn_write;
+       s->insn_read = waveform_ai_insn_read;   /* do same as AI insn_read */
 
        /* Our default loopback value is just a 0V flatline */
        for (i = 0; i < s->n_chan; i++)