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

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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>
This commit is contained in:
Ian Abbott 2015-10-27 16:59:22 +00:00 committed by Greg Kroah-Hartman
parent 3b2468fe98
commit e0c6fe1294
1 changed files with 1 additions and 0 deletions
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drivers/staging/comedi/drivers/comedi_test.c
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@ -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++)