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demo/gpct_pulse_generator: Fix some error checking

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Store the comedi_data_write() return values for channel 1 and 2 in the
'retval' variable, so that the following 'if(retval < 0) return retval;'
is meaningful.  This also avoids a compiler warning: "Identical
condition 'retval<0', second condition is always false".

Thanks to David Binderman for the bug report.
This commit is contained in:
Ian Abbott 2017-09-20 16:26:36 +01:00
parent 44c031d0f2
commit 1b988961a2
1 changed files with 2 additions and 2 deletions
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4
demo/gpct_pulse_generator.c
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@ -83,11 +83,11 @@ int ni_gpct_start_pulse_generator(comedi_t *device, unsigned subdevice, unsigned
if(retval < 0) return retval;
/* set "load a" register to the number of clock ticks the counter output should remain low
by writing to channel 1. */
comedi_data_write(device, subdevice, 1, 0, 0, down_ticks);
retval = comedi_data_write(device, subdevice, 1, 0, 0, down_ticks);
if(retval < 0) return retval;
/* set "load b" register to the number of clock ticks the counter output should remain high
by writing to channel 2 */
comedi_data_write(device, subdevice, 2, 0, 0, up_ticks);
retval = comedi_data_write(device, subdevice, 2, 0, 0, up_ticks);
if(retval < 0) return retval;
retval = comedi_arm(device, subdevice, NI_GPCT_ARM_IMMEDIATE);