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staging: comedi: drivers: introduce comedi_nscans_left()

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Introduce a helper function to determine the number of scans left in
the async command.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
H Hartley Sweeten 2014-11-05 10:31:29 -07:00 committed by Greg Kroah-Hartman
parent bc3fe15655
commit 2ee3775001
2 changed files with 41 additions and 0 deletions
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2
drivers/staging/comedi/comedidev.h
View file

@ -516,6 +516,8 @@ int comedi_dio_insn_config(struct comedi_device *, struct comedi_subdevice *,
unsigned int comedi_dio_update_state(struct comedi_subdevice *,
unsigned int *data);
unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s);
unsigned int comedi_nscans_left(struct comedi_subdevice *s,
unsigned int nscans);
void comedi_inc_scan_progress(struct comedi_subdevice *s,
unsigned int num_bytes);

39
drivers/staging/comedi/drivers.c
View file

@ -327,6 +327,45 @@ unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s)
}
EXPORT_SYMBOL_GPL(comedi_bytes_per_scan);
/**
* comedi_nscans_left - return the number of scans left in the command
* @s: comedi_subdevice struct
* @nscans: the expected number of scans
*
* If nscans is 0, the number of scans available in the async buffer will be
* used. Otherwise the expected number of scans will be used.
*
* If the async command has a stop_src of TRIG_COUNT, the nscans will be
* checked against the number of scans left in the command.
*
* The return value will then be either the expected number of scans or the
* number of scans remaining in the command.
*/
unsigned int comedi_nscans_left(struct comedi_subdevice *s,
unsigned int nscans)
{
struct comedi_async *async = s->async;
struct comedi_cmd *cmd = &async->cmd;
if (nscans == 0) {
unsigned int nbytes = comedi_buf_read_n_available(s);
nscans = nbytes / comedi_bytes_per_scan(s);
}
if (cmd->stop_src == TRIG_COUNT) {
unsigned int scans_left = 0;
if (async->scans_done < cmd->stop_arg)
scans_left = cmd->stop_arg - async->scans_done;
if (nscans > scans_left)
nscans = scans_left;
}
return nscans;
}
EXPORT_SYMBOL_GPL(comedi_nscans_left);
/**
* comedi_inc_scan_progress - update scan progress in asynchronous command
* @s: comedi_subdevice struct