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Commit 8fa8a260 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman
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staging: comedi: comedi_test: move modulo operations for waveform 



The fake waveform generator functions, `fake_sawtooth()` and
`fake_squarewave()`, called from `fake_waveform()`, have a
`current_time` parameter which is the time since the start of a waveform
period.  The parameter value may be greater than the waveform period so
they do a modulo operation to bring it into range.  Do the modulo
operations outside the functions in `waveform_ai_interrupt()` so that
the waveform generator functions always get a `current_time` parameter
less than the waveform period and do not have to do the modulo operation
themselves.  Also, only do the modulo operations when the time since the
start of a waveform exceeds the waveform period.  Usually, several
samples are produced in each waveform period and modulo operations are
typically more expensive than a simple comparison.

Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Reviewed-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 783ddaeb

drivers/staging/comedi/drivers/comedi_test.c

+10 −8
Original line number Diff line number Diff line
@@ -97,7 +97,6 @@ static unsigned short fake_sawtooth(struct comedi_device *dev, 
	binary_amplitude *= devpriv->uvolt_amplitude;

	do_div(binary_amplitude, krange->max - krange->min);



	current_time %= devpriv->usec_period;

	value = current_time;

	value *= binary_amplitude * 2;

	do_div(value, devpriv->usec_period);
@@ -125,7 +124,6 @@ static unsigned short fake_squarewave(struct comedi_device *dev, 
	const struct comedi_krange *krange =

	    &s->range_table->range[range_index];



	current_time %= devpriv->usec_period;

	value = s->maxdata;

	value *= devpriv->uvolt_amplitude;

	do_div(value, krange->max - krange->min);
@@ -206,19 +204,23 @@ static void waveform_ai_interrupt(unsigned long arg) 


	num_scans = comedi_nscans_left(s, num_scans);

	for (i = 0; i < num_scans; i++) {

		unsigned long scan_remain_period = devpriv->scan_period;



		for (j = 0; j < cmd->chanlist_len; j++) {

			unsigned short sample;



			if (devpriv->usec_current >= devpriv->usec_period)

				devpriv->usec_current %= devpriv->usec_period;

			sample = fake_waveform(dev, CR_CHAN(cmd->chanlist[j]),

					       CR_RANGE(cmd->chanlist[j]),

					       devpriv->usec_current +

						   i * devpriv->scan_period +

						   j * devpriv->convert_period);

					       devpriv->usec_current);

			comedi_buf_write_samples(s, &sample, 1);

			devpriv->usec_current += devpriv->convert_period;

			scan_remain_period -= devpriv->convert_period;

		}

		devpriv->usec_current += scan_remain_period;

	}



	devpriv->usec_current += elapsed_time;

	if (devpriv->usec_current >= devpriv->usec_period)

		devpriv->usec_current %= devpriv->usec_period;



	if (cmd->stop_src == TRIG_COUNT && async->scans_done >= cmd->stop_arg)