staging: comedi: drivers: introduce comedi_nscans_left()
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>
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@ -516,6 +516,8 @@ int comedi_dio_insn_config(struct comedi_device *, struct comedi_subdevice *,
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unsigned int comedi_dio_update_state(struct comedi_subdevice *,
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unsigned int *data);
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unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s);
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unsigned int comedi_nscans_left(struct comedi_subdevice *s,
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unsigned int nscans);
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void comedi_inc_scan_progress(struct comedi_subdevice *s,
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unsigned int num_bytes);
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@ -327,6 +327,45 @@ unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s)
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}
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EXPORT_SYMBOL_GPL(comedi_bytes_per_scan);
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/**
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* comedi_nscans_left - return the number of scans left in the command
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* @s: comedi_subdevice struct
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* @nscans: the expected number of scans
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*
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* If nscans is 0, the number of scans available in the async buffer will be
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* used. Otherwise the expected number of scans will be used.
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*
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* If the async command has a stop_src of TRIG_COUNT, the nscans will be
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* checked against the number of scans left in the command.
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*
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* The return value will then be either the expected number of scans or the
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* number of scans remaining in the command.
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*/
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unsigned int comedi_nscans_left(struct comedi_subdevice *s,
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unsigned int nscans)
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{
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struct comedi_async *async = s->async;
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struct comedi_cmd *cmd = &async->cmd;
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if (nscans == 0) {
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unsigned int nbytes = comedi_buf_read_n_available(s);
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nscans = nbytes / comedi_bytes_per_scan(s);
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}
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if (cmd->stop_src == TRIG_COUNT) {
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unsigned int scans_left = 0;
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if (async->scans_done < cmd->stop_arg)
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scans_left = cmd->stop_arg - async->scans_done;
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if (nscans > scans_left)
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nscans = scans_left;
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}
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return nscans;
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}
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EXPORT_SYMBOL_GPL(comedi_nscans_left);
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/**
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* comedi_inc_scan_progress - update scan progress in asynchronous command
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* @s: comedi_subdevice struct
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