4 files changed, 323 insertions, 152 deletions

diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
index c7c262a2d8ca..785977b40a93 100644
--- a/drivers/comedi/comedi_buf.c
+++ b/drivers/comedi/comedi_buf.c
@@ -273,19 +273,8 @@ unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s)
 	return free_end - async->buf_write_count;
 }
 
-/**
- * comedi_buf_write_alloc() - Reserve buffer space for writing
- * @s: COMEDI subdevice.
- * @nbytes: Maximum space to reserve in bytes.
- *
- * Reserve up to @nbytes bytes of space to be written in the COMEDI acquisition
- * data buffer associated with the subdevice.  The amount reserved is limited
- * by the space available.
- *
- * Return: The amount of space reserved in bytes.
- */
-unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s,
-				    unsigned int nbytes)
+unsigned int _comedi_buf_write_alloc(struct comedi_subdevice *s,
+				     unsigned int nbytes)
 {
 	struct comedi_async *async = s->async;
 	unsigned int unalloc = comedi_buf_write_n_unalloc(s);
@@ -303,6 +292,29 @@ unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s,
 
 	return nbytes;
 }
+
+/**
+ * comedi_buf_write_alloc() - Reserve buffer space for writing
+ * @s: COMEDI subdevice.
+ * @nbytes: Maximum space to reserve in bytes.
+ *
+ * Reserve up to @nbytes bytes of space to be written in the COMEDI acquisition
+ * data buffer associated with the subdevice.  The amount reserved is limited
+ * by the space available.
+ *
+ * Return: The amount of space reserved in bytes.
+ */
+unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s,
+				    unsigned int nbytes)
+{
+	if (comedi_get_is_subdevice_running(s)) {
+		nbytes = _comedi_buf_write_alloc(s, nbytes);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nbytes = 0;
+	}
+	return nbytes;
+}
 EXPORT_SYMBOL_GPL(comedi_buf_write_alloc);
 
 /*
@@ -362,6 +374,24 @@ unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s)
 	return async->buf_write_alloc_count - async->buf_write_count;
 }
 
+unsigned int _comedi_buf_write_free(struct comedi_subdevice *s,
+				    unsigned int nbytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int allocated = comedi_buf_write_n_allocated(s);
+
+	if (nbytes > allocated)
+		nbytes = allocated;
+
+	async->buf_write_count += nbytes;
+	async->buf_write_ptr += nbytes;
+	comedi_buf_munge(s, async->buf_write_count - async->munge_count);
+	if (async->buf_write_ptr >= async->prealloc_bufsz)
+		async->buf_write_ptr %= async->prealloc_bufsz;
+
+	return nbytes;
+}
+
 /**
  * comedi_buf_write_free() - Free buffer space after it is written
  * @s: COMEDI subdevice.
@@ -380,21 +410,34 @@ unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s)
 unsigned int comedi_buf_write_free(struct comedi_subdevice *s,
 				   unsigned int nbytes)
 {
+	if (comedi_get_is_subdevice_running(s)) {
+		nbytes = _comedi_buf_write_free(s, nbytes);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nbytes = 0;
+	}
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_write_free);
+
+unsigned int _comedi_buf_read_n_available(struct comedi_subdevice *s)
+{
 	struct comedi_async *async = s->async;
-	unsigned int allocated = comedi_buf_write_n_allocated(s);
+	unsigned int num_bytes;
 
-	if (nbytes > allocated)
-		nbytes = allocated;
+	if (!async)
+		return 0;
 
-	async->buf_write_count += nbytes;
-	async->buf_write_ptr += nbytes;
-	comedi_buf_munge(s, async->buf_write_count - async->munge_count);
-	if (async->buf_write_ptr >= async->prealloc_bufsz)
-		async->buf_write_ptr %= async->prealloc_bufsz;
+	num_bytes = async->munge_count - async->buf_read_count;
 
-	return nbytes;
+	/*
+	 * ensure the async buffer 'counts' are read before we
+	 * attempt to read data from the buffer
+	 */
+	smp_rmb();
+
+	return num_bytes;
 }
-EXPORT_SYMBOL_GPL(comedi_buf_write_free);
 
 /**
  * comedi_buf_read_n_available() - Determine amount of readable buffer space
@@ -409,23 +452,38 @@ EXPORT_SYMBOL_GPL(comedi_buf_write_free);
  */
 unsigned int comedi_buf_read_n_available(struct comedi_subdevice *s)
 {
-	struct comedi_async *async = s->async;
 	unsigned int num_bytes;
 
-	if (!async)
-		return 0;
+	if (comedi_get_is_subdevice_running(s)) {
+		num_bytes = _comedi_buf_read_n_available(s);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		num_bytes = 0;
+	}
+	return num_bytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_read_n_available);
 
-	num_bytes = async->munge_count - async->buf_read_count;
+unsigned int _comedi_buf_read_alloc(struct comedi_subdevice *s,
+				    unsigned int nbytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int available;
+
+	available = async->munge_count - async->buf_read_alloc_count;
+	if (nbytes > available)
+		nbytes = available;
+
+	async->buf_read_alloc_count += nbytes;
 
 	/*
 	 * ensure the async buffer 'counts' are read before we
-	 * attempt to read data from the buffer
+	 * attempt to read data from the read-alloc'ed buffer space
 	 */
 	smp_rmb();
 
-	return num_bytes;
+	return nbytes;
 }
-EXPORT_SYMBOL_GPL(comedi_buf_read_n_available);
 
 /**
  * comedi_buf_read_alloc() - Reserve buffer space for reading
@@ -445,21 +503,12 @@ EXPORT_SYMBOL_GPL(comedi_buf_read_n_available);
 unsigned int comedi_buf_read_alloc(struct comedi_subdevice *s,
 				   unsigned int nbytes)
 {
-	struct comedi_async *async = s->async;
-	unsigned int available;
-
-	available = async->munge_count - async->buf_read_alloc_count;
-	if (nbytes > available)
-		nbytes = available;
-
-	async->buf_read_alloc_count += nbytes;
-
-	/*
-	 * ensure the async buffer 'counts' are read before we
-	 * attempt to read data from the read-alloc'ed buffer space
-	 */
-	smp_rmb();
-
+	if (comedi_get_is_subdevice_running(s)) {
+		nbytes = _comedi_buf_read_alloc(s, nbytes);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nbytes = 0;
+	}
 	return nbytes;
 }
 EXPORT_SYMBOL_GPL(comedi_buf_read_alloc);
@@ -469,21 +518,8 @@ static unsigned int comedi_buf_read_n_allocated(struct comedi_async *async)
 	return async->buf_read_alloc_count - async->buf_read_count;
 }
 
-/**
- * comedi_buf_read_free() - Free buffer space after it has been read
- * @s: COMEDI subdevice.
- * @nbytes: Maximum space to free in bytes.
- *
- * Free up to @nbytes bytes of buffer space previously reserved for reading in
- * the COMEDI acquisition data buffer associated with the subdevice.  The
- * amount of space freed is limited to the amount that was reserved.
- *
- * The freed space becomes available for allocation by the writer.
- *
- * Return: The amount of space freed in bytes.
- */
-unsigned int comedi_buf_read_free(struct comedi_subdevice *s,
-				  unsigned int nbytes)
+unsigned int _comedi_buf_read_free(struct comedi_subdevice *s,
+				   unsigned int nbytes)
 {
 	struct comedi_async *async = s->async;
 	unsigned int allocated;
@@ -503,6 +539,31 @@ unsigned int comedi_buf_read_free(struct comedi_subdevice *s,
 	async->buf_read_ptr %= async->prealloc_bufsz;
 	return nbytes;
 }
+
+/**
+ * comedi_buf_read_free() - Free buffer space after it has been read
+ * @s: COMEDI subdevice.
+ * @nbytes: Maximum space to free in bytes.
+ *
+ * Free up to @nbytes bytes of buffer space previously reserved for reading in
+ * the COMEDI acquisition data buffer associated with the subdevice.  The
+ * amount of space freed is limited to the amount that was reserved.
+ *
+ * The freed space becomes available for allocation by the writer.
+ *
+ * Return: The amount of space freed in bytes.
+ */
+unsigned int comedi_buf_read_free(struct comedi_subdevice *s,
+				  unsigned int nbytes)
+{
+	if (comedi_get_is_subdevice_running(s)) {
+		nbytes = _comedi_buf_read_free(s, nbytes);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nbytes = 0;
+	}
+	return nbytes;
+}
 EXPORT_SYMBOL_GPL(comedi_buf_read_free);
 
 static void comedi_buf_memcpy_to(struct comedi_subdevice *s,
@@ -558,6 +619,38 @@ static void comedi_buf_memcpy_from(struct comedi_subdevice *s,
 	}
 }
 
+static unsigned int _comedi_buf_write_samples(struct comedi_subdevice *s,
+					      const void *data,
+					      unsigned int nsamples)
+{
+	unsigned int max_samples;
+	unsigned int nbytes;
+
+	/*
+	 * Make sure there is enough room in the buffer for all the samples.
+	 * If not, clamp the nsamples to the number that will fit, flag the
+	 * buffer overrun and add the samples that fit.
+	 */
+	max_samples = comedi_bytes_to_samples(s, comedi_buf_write_n_unalloc(s));
+	if (nsamples > max_samples) {
+		dev_warn(s->device->class_dev, "buffer overrun\n");
+		s->async->events |= COMEDI_CB_OVERFLOW;
+		nsamples = max_samples;
+	}
+
+	if (nsamples == 0)
+		return 0;
+
+	nbytes = comedi_samples_to_bytes(s, nsamples);
+	nbytes = _comedi_buf_write_alloc(s, nbytes);
+	comedi_buf_memcpy_to(s, data, nbytes);
+	_comedi_buf_write_free(s, nbytes);
+	_comedi_inc_scan_progress(s, nbytes);
+	s->async->events |= COMEDI_CB_BLOCK;
+
+	return nbytes;
+}
+
 /**
  * comedi_buf_write_samples() - Write sample data to COMEDI buffer
  * @s: COMEDI subdevice.
@@ -578,34 +671,42 @@ static void comedi_buf_memcpy_from(struct comedi_subdevice *s,
 unsigned int comedi_buf_write_samples(struct comedi_subdevice *s,
 				      const void *data, unsigned int nsamples)
 {
+	unsigned int nbytes;
+
+	if (comedi_get_is_subdevice_running(s)) {
+		nbytes = _comedi_buf_write_samples(s, data, nsamples);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nbytes = 0;
+	}
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_write_samples);
+
+static unsigned int _comedi_buf_read_samples(struct comedi_subdevice *s,
+					    void *data, unsigned int nsamples)
+{
 	unsigned int max_samples;
 	unsigned int nbytes;
 
-	/*
-	 * Make sure there is enough room in the buffer for all the samples.
-	 * If not, clamp the nsamples to the number that will fit, flag the
-	 * buffer overrun and add the samples that fit.
-	 */
-	max_samples = comedi_bytes_to_samples(s, comedi_buf_write_n_unalloc(s));
-	if (nsamples > max_samples) {
-		dev_warn(s->device->class_dev, "buffer overrun\n");
-		s->async->events |= COMEDI_CB_OVERFLOW;
+	/* clamp nsamples to the number of full samples available */
+	max_samples = comedi_bytes_to_samples(s,
+					      _comedi_buf_read_n_available(s));
+	if (nsamples > max_samples)
 		nsamples = max_samples;
-	}
 
 	if (nsamples == 0)
 		return 0;
 
-	nbytes = comedi_buf_write_alloc(s,
+	nbytes = _comedi_buf_read_alloc(s,
 					comedi_samples_to_bytes(s, nsamples));
-	comedi_buf_memcpy_to(s, data, nbytes);
-	comedi_buf_write_free(s, nbytes);
-	comedi_inc_scan_progress(s, nbytes);
+	comedi_buf_memcpy_from(s, data, nbytes);
+	_comedi_buf_read_free(s, nbytes);
+	_comedi_inc_scan_progress(s, nbytes);
 	s->async->events |= COMEDI_CB_BLOCK;
 
 	return nbytes;
 }
-EXPORT_SYMBOL_GPL(comedi_buf_write_samples);
 
 /**
  * comedi_buf_read_samples() - Read sample data from COMEDI buffer
@@ -624,25 +725,14 @@ EXPORT_SYMBOL_GPL(comedi_buf_write_samples);
 unsigned int comedi_buf_read_samples(struct comedi_subdevice *s,
 				     void *data, unsigned int nsamples)
 {
-	unsigned int max_samples;
 	unsigned int nbytes;
 
-	/* clamp nsamples to the number of full samples available */
-	max_samples = comedi_bytes_to_samples(s,
-					      comedi_buf_read_n_available(s));
-	if (nsamples > max_samples)
-		nsamples = max_samples;
-
-	if (nsamples == 0)
-		return 0;
-
-	nbytes = comedi_buf_read_alloc(s,
-				       comedi_samples_to_bytes(s, nsamples));
-	comedi_buf_memcpy_from(s, data, nbytes);
-	comedi_buf_read_free(s, nbytes);
-	comedi_inc_scan_progress(s, nbytes);
-	s->async->events |= COMEDI_CB_BLOCK;
-
+	if (comedi_get_is_subdevice_running(s)) {
+		nbytes = _comedi_buf_read_samples(s, data, nsamples);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nbytes = 0;
+	}
 	return nbytes;
 }
 EXPORT_SYMBOL_GPL(comedi_buf_read_samples);
diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c
index 8253e4e8232b..657c98cd723e 100644
--- a/drivers/comedi/comedi_fops.c
+++ b/drivers/comedi/comedi_fops.c
@@ -1206,15 +1206,15 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 	if (!(async->cmd.flags & CMDF_WRITE)) {
 		/* command was set up in "read" direction */
 		if (bi.bytes_read) {
-			comedi_buf_read_alloc(s, bi.bytes_read);
-			bi.bytes_read = comedi_buf_read_free(s, bi.bytes_read);
+			_comedi_buf_read_alloc(s, bi.bytes_read);
+			bi.bytes_read = _comedi_buf_read_free(s, bi.bytes_read);
 		}
 		/*
 		 * If nothing left to read, and command has stopped, and
 		 * {"read" position not updated or command stopped normally},
 		 * then become non-busy.
 		 */
-		if (comedi_buf_read_n_available(s) == 0 &&
+		if (_comedi_buf_read_n_available(s) == 0 &&
 		    !comedi_is_runflags_running(runflags) &&
 		    (bi.bytes_read == 0 ||
 		     !comedi_is_runflags_in_error(runflags))) {
@@ -1231,9 +1231,9 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 			if (comedi_is_runflags_in_error(runflags))
 				retval = -EPIPE;
 		} else if (bi.bytes_written) {
-			comedi_buf_write_alloc(s, bi.bytes_written);
+			_comedi_buf_write_alloc(s, bi.bytes_written);
 			bi.bytes_written =
-			    comedi_buf_write_free(s, bi.bytes_written);
+			    _comedi_buf_write_free(s, bi.bytes_written);
 		}
 		bi.bytes_read = 0;
 	}
@@ -2569,7 +2569,7 @@ static __poll_t comedi_poll(struct file *file, poll_table *wait)
 		poll_wait(file, &s->async->wait_head, wait);
 		if (s->busy != file || !comedi_is_subdevice_running(s) ||
 		    (s->async->cmd.flags & CMDF_WRITE) ||
-		    comedi_buf_read_n_available(s) > 0)
+		    _comedi_buf_read_n_available(s) > 0)
 			mask |= EPOLLIN | EPOLLRDNORM;
 	}
 
@@ -2702,7 +2702,7 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
 			break;
 
 		/* Allocate all free buffer space. */
-		comedi_buf_write_alloc(s, async->prealloc_bufsz);
+		_comedi_buf_write_alloc(s, async->prealloc_bufsz);
 		m = comedi_buf_write_n_allocated(s);
 		n = min_t(size_t, m, nbytes);
 
@@ -2730,7 +2730,7 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
 			n -= m;
 			retval = -EFAULT;
 		}
-		comedi_buf_write_free(s, n);
+		_comedi_buf_write_free(s, n);
 
 		count += n;
 		nbytes -= n;
@@ -2816,7 +2816,7 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
 	while (count == 0 && !retval) {
 		set_current_state(TASK_INTERRUPTIBLE);
 
-		m = comedi_buf_read_n_available(s);
+		m = _comedi_buf_read_n_available(s);
 		n = min_t(size_t, m, nbytes);
 
 		if (n == 0) {
@@ -2856,8 +2856,8 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
 			retval = -EFAULT;
 		}
 
-		comedi_buf_read_alloc(s, n);
-		comedi_buf_read_free(s, n);
+		_comedi_buf_read_alloc(s, n);
+		_comedi_buf_read_free(s, n);
 
 		count += n;
 		nbytes -= n;
@@ -2891,7 +2891,7 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
 		    s == new_s && new_s->async == async && s->busy == file &&
 		    !(async->cmd.flags & CMDF_WRITE) &&
 		    !comedi_is_subdevice_running(s) &&
-		    comedi_buf_read_n_available(s) == 0)
+		    _comedi_buf_read_n_available(s) == 0)
 			do_become_nonbusy(dev, s);
 		mutex_unlock(&dev->mutex);
 	}
@@ -3386,18 +3386,7 @@ static const struct file_operations comedi_fops = {
 	.llseek = noop_llseek,
 };
 
-/**
- * comedi_event() - Handle events for asynchronous COMEDI command
- * @dev: COMEDI device.
- * @s: COMEDI subdevice.
- * Context: in_interrupt() (usually), @s->spin_lock spin-lock not held.
- *
- * If an asynchronous COMEDI command is active on the subdevice, process
- * any %COMEDI_CB_... event flags that have been set, usually by an
- * interrupt handler.  These may change the run state of the asynchronous
- * command, wake a task, and/or send a %SIGIO signal.
- */
-void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
+void _comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
 {
 	struct comedi_async *async = s->async;
 	unsigned int events;
@@ -3433,6 +3422,25 @@ void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
 	if (si_code)
 		kill_fasync(&dev->async_queue, SIGIO, si_code);
 }
+
+/**
+ * comedi_event() - Handle events for asynchronous COMEDI command
+ * @dev: COMEDI device.
+ * @s: COMEDI subdevice.
+ * Context: in_interrupt() (usually), @s->spin_lock spin-lock not held.
+ *
+ * If an asynchronous COMEDI command is active on the subdevice, process
+ * any %COMEDI_CB_... event flags that have been set, usually by an
+ * interrupt handler.  These may change the run state of the asynchronous
+ * command, wake a task, and/or send a %SIGIO signal.
+ */
+void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
+{
+	if (comedi_get_is_subdevice_running(s)) {
+		comedi_event(dev, s);
+		comedi_put_is_subdevice_running(s);
+	}
+}
 EXPORT_SYMBOL_GPL(comedi_event);
 
 /* Note: the ->mutex is pre-locked on successful return */
diff --git a/drivers/comedi/comedi_internal.h b/drivers/comedi/comedi_internal.h
index cf10ba016ebc..41a3b09f8f05 100644
--- a/drivers/comedi/comedi_internal.h
+++ b/drivers/comedi/comedi_internal.h
@@ -36,6 +36,18 @@ struct comedi_buf_map *
 comedi_buf_map_from_subdev_get(struct comedi_subdevice *s);
 unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s);
 unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s);
+unsigned int _comedi_buf_write_alloc(struct comedi_subdevice *s,
+				     unsigned int nbytes);
+unsigned int _comedi_buf_write_free(struct comedi_subdevice *s,
+				    unsigned int nbytes);
+unsigned int _comedi_buf_read_n_available(struct comedi_subdevice *s);
+unsigned int _comedi_buf_read_alloc(struct comedi_subdevice *s,
+				    unsigned int nbytes);
+unsigned int _comedi_buf_read_free(struct comedi_subdevice *s,
+				   unsigned int nbytes);
+void _comedi_inc_scan_progress(struct comedi_subdevice *s,
+			       unsigned int num_bytes);
+void _comedi_event(struct comedi_device *dev, struct comedi_subdevice *s);
 void comedi_device_cancel_all(struct comedi_device *dev);
 bool comedi_can_auto_free_spriv(struct comedi_subdevice *s);
 
diff --git a/drivers/comedi/drivers.c b/drivers/comedi/drivers.c
index fd6e6cbe47ad..69cd2a253c66 100644
--- a/drivers/comedi/drivers.c
+++ b/drivers/comedi/drivers.c
@@ -441,6 +441,13 @@ unsigned int comedi_bytes_per_scan_cmd(struct comedi_subdevice *s,
 }
 EXPORT_SYMBOL_GPL(comedi_bytes_per_scan_cmd);
 
+static 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);
+}
+
 /**
  * comedi_bytes_per_scan() - Get length of asynchronous command "scan" in bytes
  * @s: COMEDI subdevice.
@@ -458,9 +465,16 @@ EXPORT_SYMBOL_GPL(comedi_bytes_per_scan_cmd);
  */
 unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s)
 {
-	struct comedi_cmd *cmd = &s->async->cmd;
+	unsigned int num_bytes;
 
-	return comedi_bytes_per_scan_cmd(s, cmd);
+	if (comedi_get_is_subdevice_running(s)) {
+		num_bytes = _comedi_bytes_per_scan(s);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		/* Use nomimal, single sample scan length. */
+		num_bytes = comedi_samples_to_bytes(s, 1);
+	}
+	return num_bytes;
 }
 EXPORT_SYMBOL_GPL(comedi_bytes_per_scan);
 
@@ -482,6 +496,17 @@ static unsigned int __comedi_nscans_left(struct comedi_subdevice *s,
 	return nscans;
 }
 
+static unsigned int _comedi_nscans_left(struct comedi_subdevice *s,
+					unsigned int nscans)
+{
+	if (nscans == 0) {
+		unsigned int nbytes = _comedi_buf_read_n_available(s);
+
+		nscans = nbytes / _comedi_bytes_per_scan(s);
+	}
+	return __comedi_nscans_left(s, nscans);
+}
+
 /**
  * comedi_nscans_left() - Return the number of scans left in the command
  * @s: COMEDI subdevice.
@@ -499,25 +524,18 @@ static unsigned int __comedi_nscans_left(struct comedi_subdevice *s,
 unsigned int comedi_nscans_left(struct comedi_subdevice *s,
 				unsigned int nscans)
 {
-	if (nscans == 0) {
-		unsigned int nbytes = comedi_buf_read_n_available(s);
-
-		nscans = nbytes / comedi_bytes_per_scan(s);
+	if (comedi_get_is_subdevice_running(s)) {
+		nscans = _comedi_nscans_left(s, nscans);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nscans = 0;
 	}
-	return __comedi_nscans_left(s, nscans);
+	return nscans;
 }
 EXPORT_SYMBOL_GPL(comedi_nscans_left);
 
-/**
- * comedi_nsamples_left() - Return the number of samples left in the command
- * @s: COMEDI subdevice.
- * @nsamples: The expected number of samples.
- *
- * Returns the number of samples remaining to complete the command, or the
- * specified expected number of samples (@nsamples), whichever is fewer.
- */
-unsigned int comedi_nsamples_left(struct comedi_subdevice *s,
-				  unsigned int nsamples)
+static unsigned int _comedi_nsamples_left(struct comedi_subdevice *s,
+					  unsigned int nsamples)
 {
 	struct comedi_async *async = s->async;
 	struct comedi_cmd *cmd = &async->cmd;
@@ -538,24 +556,34 @@ unsigned int comedi_nsamples_left(struct comedi_subdevice *s,
 		return samples_left;
 	return nsamples;
 }
-EXPORT_SYMBOL_GPL(comedi_nsamples_left);
 
 /**
- * comedi_inc_scan_progress() - Update scan progress in asynchronous command
+ * comedi_nsamples_left() - Return the number of samples left in the command
  * @s: COMEDI subdevice.
- * @num_bytes: Amount of data in bytes to increment scan progress.
+ * @nsamples: The expected number of samples.
  *
- * Increments the scan progress by the number of bytes specified by @num_bytes.
- * If the scan progress reaches or exceeds the scan length in bytes, reduce
- * it modulo the scan length in bytes and set the "end of scan" asynchronous
- * event flag (%COMEDI_CB_EOS) to be processed later.
+ * Returns the number of samples remaining to complete the command, or the
+ * specified expected number of samples (@nsamples), whichever is fewer.
  */
-void comedi_inc_scan_progress(struct comedi_subdevice *s,
-			      unsigned int num_bytes)
+unsigned int comedi_nsamples_left(struct comedi_subdevice *s,
+				  unsigned int nsamples)
+{
+	if (comedi_get_is_subdevice_running(s)) {
+		nsamples = _comedi_nsamples_left(s, nsamples);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		nsamples = 0;
+	}
+	return nsamples;
+}
+EXPORT_SYMBOL_GPL(comedi_nsamples_left);
+
+void _comedi_inc_scan_progress(struct comedi_subdevice *s,
+			       unsigned int num_bytes)
 {
 	struct comedi_async *async = s->async;
 	struct comedi_cmd *cmd = &async->cmd;
-	unsigned int scan_length = comedi_bytes_per_scan(s);
+	unsigned int scan_length = _comedi_bytes_per_scan(s);
 
 	/* track the 'cur_chan' for non-SDF_PACKED subdevices */
 	if (!(s->subdev_flags & SDF_PACKED)) {
@@ -576,8 +604,43 @@ void comedi_inc_scan_progress(struct comedi_subdevice *s,
 		async->events |= COMEDI_CB_EOS;
 	}
 }
+
+/**
+ * comedi_inc_scan_progress() - Update scan progress in asynchronous command
+ * @s: COMEDI subdevice.
+ * @num_bytes: Amount of data in bytes to increment scan progress.
+ *
+ * Increments the scan progress by the number of bytes specified by @num_bytes.
+ * If the scan progress reaches or exceeds the scan length in bytes, reduce
+ * it modulo the scan length in bytes and set the "end of scan" asynchronous
+ * event flag (%COMEDI_CB_EOS) to be processed later.
+ */
+void comedi_inc_scan_progress(struct comedi_subdevice *s,
+			      unsigned int num_bytes)
+{
+	if (comedi_get_is_subdevice_running(s)) {
+		_comedi_inc_scan_progress(s, num_bytes);
+		comedi_put_is_subdevice_running(s);
+	}
+}
 EXPORT_SYMBOL_GPL(comedi_inc_scan_progress);
 
+static unsigned int _comedi_handle_events(struct comedi_device *dev,
+					  struct comedi_subdevice *s)
+{
+	unsigned int events = s->async->events;
+
+	if (events == 0)
+		return events;
+
+	if ((events & COMEDI_CB_CANCEL_MASK) && s->cancel)
+		s->cancel(dev, s);
+
+	_comedi_event(dev, s);
+
+	return events;
+}
+
 /**
  * comedi_handle_events() - Handle events and possibly stop acquisition
  * @dev: COMEDI device.
@@ -597,16 +660,14 @@ EXPORT_SYMBOL_GPL(comedi_inc_scan_progress);
 unsigned int comedi_handle_events(struct comedi_device *dev,
 				  struct comedi_subdevice *s)
 {
-	unsigned int events = s->async->events;
-
-	if (events == 0)
-		return events;
-
-	if ((events & COMEDI_CB_CANCEL_MASK) && s->cancel)
-		s->cancel(dev, s);
-
-	comedi_event(dev, s);
+	unsigned int events;
 
+	if (comedi_get_is_subdevice_running(s)) {
+		events = _comedi_handle_events(dev, s);
+		comedi_put_is_subdevice_running(s);
+	} else {
+		events = 0;
+	}
 	return events;
 }
 EXPORT_SYMBOL_GPL(comedi_handle_events);