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Commit 5e5a21cf authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: das1800: tidy up das1800_ai_transfer_size() 



For aesthetics, pass the fill time 'ns' as a parameter to this function.

Refactor this function to calculate the transfer size in 'samples' instead
of 'bytes'. This removes the need to constantly multiply the values by the
'sample_size'. It also helps avoid any possible integer overflow issues.

Use the comedi_nsamples_left() helper to limit the samples when cmd->stop_src
is TRIG_COUNT.

Use comedi_samples_to_bytes() to return the final DMA size in bytes.

Signed-off-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 620ec185

drivers/staging/comedi/drivers/das1800.c

+19 −26
Original line number Diff line number Diff line
@@ -967,42 +967,35 @@ static void das1800_setup_counters(struct comedi_device *dev, 
}



static unsigned int das1800_ai_transfer_size(struct comedi_device *dev,

					     struct comedi_subdevice *s)

					     struct comedi_subdevice *s,

					     unsigned int ns)

{

	struct comedi_cmd *cmd = &s->async->cmd;

	unsigned int size = DMA_BUF_SIZE;

	unsigned int sample_size = comedi_bytes_per_sample(s);

	unsigned int fill_time = 300000000;	/*  target time in nanoseconds for filling dma buffer */

	unsigned int max_size;	/*  maximum size we will allow for a transfer */

	unsigned int max_samples = comedi_bytes_to_samples(s, DMA_BUF_SIZE);

	unsigned int samples;



	samples = max_samples;



	/*  make dma buffer fill in 0.3 seconds for timed modes */

	/* for timed modes, make dma buffer fill in 'ns' time */

	switch (cmd->scan_begin_src) {

	case TRIG_FOLLOW:	/* not in burst mode */

		if (cmd->convert_src == TRIG_TIMER)

			size = (fill_time / cmd->convert_arg) * sample_size;

			samples = ns / cmd->convert_arg;

		break;

	case TRIG_TIMER:

		size = (fill_time / (cmd->scan_begin_arg * cmd->chanlist_len)) *

		    sample_size;

		break;

	default:

		size = DMA_BUF_SIZE;

		samples = ns / (cmd->scan_begin_arg * cmd->chanlist_len);

		break;

	}



	/*  set a minimum and maximum size allowed */

	max_size = DMA_BUF_SIZE;

	/*  if we are taking limited number of conversions, limit transfer size to that */

	if (cmd->stop_src == TRIG_COUNT &&

	    cmd->stop_arg * cmd->chanlist_len * sample_size < max_size)

		max_size = cmd->stop_arg * cmd->chanlist_len * sample_size;

	/* limit samples to what is remaining in the command */

	samples = comedi_nsamples_left(s, samples);



	if (size > max_size)

		size = max_size;

	if (size < sample_size)

		size = sample_size;

	if (samples > max_samples)

		samples = max_samples;

	if (samples < 1)

		samples = 1;



	return size;

	return comedi_samples_to_bytes(s, samples);

}



static void das1800_ai_setup_dma(struct comedi_device *dev,
@@ -1017,8 +1010,8 @@ static void das1800_ai_setup_dma(struct comedi_device *dev, 


	devpriv->cur_dma = 0;



	/* determine a reasonable dma transfer size */

	bytes = das1800_ai_transfer_size(dev, s);

	/* determine a dma transfer size to fill buffer in 0.3 sec */

	bytes = das1800_ai_transfer_size(dev, s, 300000000);



	dma->size = bytes;

	das1800_isadma_program(dma);