staging: comedi: add comedi_read_array_from_buffer()

The "comedi_fc" module contains a few functions useful to Comedi
drivers.  Their functionality is being migrated to the core "comedi"
module and renamed to start with the prefix `comedi_`.  As part of this
migration, move `cfc_read_array_from_buffer()` into the core comedi
module and rename it to `comedi_read_array_from_buffer()`.  Change the
external declaration of `cfc_read_array_from_buffer()` into an inline
function that calls `comedi_read_array_from_buffer()`.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index 52a75d2238dc..c3f5751086a0 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -547,3 +547,30 @@ unsigned int comedi_write_array_to_buffer(struct comedi_subdevice *s,
 	return num_bytes;
 }
 EXPORT_SYMBOL_GPL(comedi_write_array_to_buffer);
+
+/**
+ * comedi_read_array_from_buffer - read data from comedi buffer
+ * @s: comedi_subdevice struct
+ * @data: destination
+ * @num_bytes: number of bytes to read
+ *
+ * Reads up to num_bytes bytes of data from the comedi buffer associated with
+ * the subdevice, marks it as read and updates the acquisition scan progress.
+ *
+ * Returns the amount of data read in bytes.
+ */
+unsigned int comedi_read_array_from_buffer(struct comedi_subdevice *s,
+					   void *data, unsigned int num_bytes)
+{
+	if (num_bytes == 0)
+		return 0;
+
+	num_bytes = comedi_buf_read_alloc(s, num_bytes);
+	comedi_buf_memcpy_from(s, 0, data, num_bytes);
+	comedi_buf_read_free(s, num_bytes);
+	comedi_inc_scan_progress(s, num_bytes);
+	s->async->events |= COMEDI_CB_BLOCK;
+
+	return num_bytes;
+}
+EXPORT_SYMBOL_GPL(comedi_read_array_from_buffer);