diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h
index 1bb9986f865e..33f249af0063 100644
--- a/drivers/staging/comedi/comedidev.h
+++ b/drivers/staging/comedi/comedidev.h
@@ -992,6 +992,8 @@ int comedi_dio_insn_config(struct comedi_device *dev,
 			   unsigned int mask);
 unsigned int comedi_dio_update_state(struct comedi_subdevice *s,
 				     unsigned int *data);
+unsigned int comedi_bytes_per_scan_cmd(struct comedi_subdevice *s,
+				       struct comedi_cmd *cmd);
 unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s);
 unsigned int comedi_nscans_left(struct comedi_subdevice *s,
 				unsigned int nscans);
diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index c11c22bd6d13..2e532219f08b 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -390,11 +390,13 @@ unsigned int comedi_dio_update_state(struct comedi_subdevice *s,
 EXPORT_SYMBOL_GPL(comedi_dio_update_state);
 
 /**
- * comedi_bytes_per_scan() - Get length of asynchronous command "scan" in bytes
+ * comedi_bytes_per_scan_cmd() - Get length of asynchronous command "scan" in
+ * bytes
  * @s: COMEDI subdevice.
+ * @cmd: COMEDI command.
  *
  * Determines the overall scan length according to the subdevice type and the
- * number of channels in the scan.
+ * number of channels in the scan for the specified command.
  *
  * For digital input, output or input/output subdevices, samples for
  * multiple channels are assumed to be packed into one or more unsigned
@@ -404,9 +406,9 @@ EXPORT_SYMBOL_GPL(comedi_dio_update_state);
  *
  * Returns the overall scan length in bytes.
  */
-unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s)
+unsigned int comedi_bytes_per_scan_cmd(struct comedi_subdevice *s,
+				       struct comedi_cmd *cmd)
 {
-	struct comedi_cmd *cmd = &s->async->cmd;
 	unsigned int num_samples;
 	unsigned int bits_per_sample;
 
@@ -423,6 +425,29 @@ unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s)
 	}
 	return comedi_samples_to_bytes(s, num_samples);
 }
+EXPORT_SYMBOL_GPL(comedi_bytes_per_scan_cmd);
+
+/**
+ * comedi_bytes_per_scan() - Get length of asynchronous command "scan" in bytes
+ * @s: COMEDI subdevice.
+ *
+ * Determines the overall scan length according to the subdevice type and the
+ * number of channels in the scan for the current command.
+ *
+ * For digital input, output or input/output subdevices, samples for
+ * multiple channels are assumed to be packed into one or more unsigned
+ * short or unsigned int values according to the subdevice's %SDF_LSAMPL
+ * flag.  For other types of subdevice, samples are assumed to occupy a
+ * whole unsigned short or unsigned int according to the %SDF_LSAMPL flag.
+ *
+ * Returns the overall scan length in bytes.
+ */
+unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s)
+{
+	struct comedi_cmd *cmd = &s->async->cmd;
+
+	return comedi_bytes_per_scan_cmd(s, cmd);
+}
 EXPORT_SYMBOL_GPL(comedi_bytes_per_scan);
 
 static unsigned int __comedi_nscans_left(struct comedi_subdevice *s,
diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c
index 158f3e83efb6..36361bdf934a 100644
--- a/drivers/staging/comedi/drivers/ni_mio_common.c
+++ b/drivers/staging/comedi/drivers/ni_mio_common.c
@@ -3523,6 +3523,7 @@ static int ni_cdio_check_chanlist(struct comedi_device *dev,
 static int ni_cdio_cmdtest(struct comedi_device *dev,
 			   struct comedi_subdevice *s, struct comedi_cmd *cmd)
 {
+	unsigned int bytes_per_scan;
 	int err = 0;
 	int tmp;
 
@@ -3552,9 +3553,12 @@ static int ni_cdio_cmdtest(struct comedi_device *dev,
 	err |= comedi_check_trigger_arg_is(&cmd->convert_arg, 0);
 	err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
 					   cmd->chanlist_len);
-	err |= comedi_check_trigger_arg_max(&cmd->stop_arg,
-					    s->async->prealloc_bufsz /
-					    comedi_bytes_per_scan(s));
+	bytes_per_scan = comedi_bytes_per_scan_cmd(s, cmd);
+	if (bytes_per_scan) {
+		err |= comedi_check_trigger_arg_max(&cmd->stop_arg,
+						    s->async->prealloc_bufsz /
+						    bytes_per_scan);
+	}
 
 	if (err)
 		return 3;