staging: iio: Add a bits per element element to ring_generic allowing a general ring_sw_preenable_function.

Signed-off-by: Barry Song <21cnbao@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/ring_generic.h

@@ -100,6 +100,7 @@ struct iio_ring_access_funcs {
  * @access_id:		device id number
  * @length:		[DEVICE] number of datums in ring
  * @bpd:		[DEVICE] size of individual datum including timestamp
+ * @bpe:		[DEVICE] size of individual channel value
  * @loopcount:		[INTERN] number of times the ring has looped
  * @access_handler:	[INTERN] chrdev access handling
  * @ev_int:		[INTERN] chrdev interface for the event chrdev
@@ -121,6 +122,7 @@ struct iio_ring_buffer {
 	int				access_id;
 	int				length;
 	int				bpd;
+	int				bpe;
 	int				loopcount;
 	struct iio_handler		access_handler;
 	struct iio_event_interface	ev_int;

drivers/staging/iio/ring_sw.c

@@ -431,5 +431,30 @@ void iio_sw_rb_free(struct iio_ring_buffer *r)
 		iio_put_ring_buffer(r);
 }
 EXPORT_SYMBOL(iio_sw_rb_free);
+
+int iio_sw_ring_preenable(struct iio_dev *indio_dev)
+{
+	size_t size;
+	dev_dbg(&indio_dev->dev, "%s\n", __func__);
+	/* Check if there are any scan elements enabled, if not fail*/
+	if (!(indio_dev->scan_count || indio_dev->scan_timestamp))
+		return -EINVAL;
+	if (indio_dev->scan_timestamp)
+		if (indio_dev->scan_count)
+			/* Timestamp (aligned to s64) and data */
+			size = (((indio_dev->scan_count * indio_dev->ring->bpe)
+					+ sizeof(s64) - 1)
+				& ~(sizeof(s64) - 1))
+				+ sizeof(s64);
+		else /* Timestamp only  */
+			size = sizeof(s64);
+	else /* Data only */
+		size = indio_dev->scan_count * indio_dev->ring->bpe;
+	indio_dev->ring->access.set_bpd(indio_dev->ring, size);
+
+	return 0;
+}
+EXPORT_SYMBOL(iio_sw_ring_preenable);
+
 MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
 MODULE_LICENSE("GPL");

drivers/staging/iio/ring_sw.h

@@ -207,7 +207,7 @@ struct iio_sw_ring_buffer {
 struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev);
 void iio_sw_rb_free(struct iio_ring_buffer *ring);
 
-
+int iio_sw_ring_preenable(struct iio_dev *indio_dev);
 
 #else /* CONFIG_IIO_RING_BUFFER*/
 static inline void iio_ring_sw_register_funcs(struct iio_ring_access_funcs *ra)