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>

diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h
index b5e0ec3..616e9b0 100644 (file)
--- a/drivers/staging/comedi/comedidev.h
+++ b/drivers/staging/comedi/comedidev.h
@@ -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);
 

diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index 02a01ba..00194a5 100644 (file)
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -328,6 +328,45 @@ 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
  * @num_bytes: amount of data in bytes to increment scan progress