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: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
Cc: Ian Abbott <abbotti@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/comedi/drivers/das1800.c | 45 ++++++++++++++------------------
1 file changed, 19 insertions(+), 26 deletions(-)
diff --git a/drivers/staging/comedi/drivers/das1800.c b/drivers/staging/comedi/drivers/das1800.c
index c36ce0c..5be5162 100644
--- a/drivers/staging/comedi/drivers/das1800.c
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -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;
- /* make dma buffer fill in 0.3 seconds for timed modes */
+ samples = max_samples;
+
+ /* for timed modes, make dma buffer fill in 'ns' time */
switch (cmd->scan_begin_src) {
- case TRIG_FOLLOW: /* not in burst mode */
+ 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);
--
2.0.3
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