iio: buffer: Drop get_length callback

We already do have the length field in the struct iio_buffer which is
expected to be in sync with the current size of the buffer. And currently
all implementations of the get_length callback either return this field or a
constant number.

This patch removes the get_length callback and replaces all occurrences in
the IIO core with directly accessing the length field of the buffer.

Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/industrialio-buffer.c

···
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct iio_buffer *buffer = indio_dev->buffer;
 
-	if (buffer->access->get_length)
-		return sprintf(buf, "%d\n",
-			       buffer->access->get_length(buffer));
-
-	return 0;
+	return sprintf(buf, "%d\n", buffer->length);
 }
 
 static ssize_t iio_buffer_write_length(struct device *dev,
···
 	if (ret)
 		return ret;
 
-	if (buffer->access->get_length)
-		if (val == buffer->access->get_length(buffer))
-			return len;
+	if (val == buffer->length)
+		return len;
 
 	mutex_lock(&indio_dev->mlock);
 	if (iio_buffer_is_active(indio_dev->buffer)) {

drivers/iio/kfifo_buf.c

···
 	return ret;
 }
 
-static int iio_get_length_kfifo(struct iio_buffer *r)
-{
-	return r->length;
-}
-
 static int iio_mark_update_needed_kfifo(struct iio_buffer *r)
 {
 	struct iio_kfifo *kf = iio_to_kfifo(r);
···
 	.data_available = iio_kfifo_buf_data_available,
 	.request_update = &iio_request_update_kfifo,
 	.set_bytes_per_datum = &iio_set_bytes_per_datum_kfifo,
-	.get_length = &iio_get_length_kfifo,
 	.set_length = &iio_set_length_kfifo,
 	.release = &iio_kfifo_buffer_release,
 };

drivers/staging/iio/Documentation/ring.txt

···
 set_bytes_per_datum
   Set the number of bytes for a complete scan. (All samples + timestamp)
 
-get_length / set_length
-  Get/set the number of complete scans that may be held by the buffer.
+set_length
+  Set the number of complete scans that may be held by the buffer.
 

drivers/staging/iio/accel/sca3000_ring.c

···
 	return ret ? ret : num_read;
 }
 
-/* This is only valid with all 3 elements enabled */
-static int sca3000_ring_get_length(struct iio_buffer *r)
-{
-	return 64;
-}
-
 static bool sca3000_ring_buf_data_available(struct iio_buffer *r)
 {
 	return r->stufftoread;
···
 	ring->private = indio_dev;
 	buf = &ring->buf;
 	buf->stufftoread = 0;
+	buf->length = 64;
 	buf->attrs = sca3000_ring_attributes;
 	iio_buffer_init(buf);
 
···
 
 static const struct iio_buffer_access_funcs sca3000_ring_access_funcs = {
 	.read_first_n = &sca3000_read_first_n_hw_rb,
-	.get_length = &sca3000_ring_get_length,
 	.data_available = sca3000_ring_buf_data_available,
 	.release = sca3000_ring_release,
 };

include/linux/iio/buffer.h

···
  * @request_update:	if a parameter change has been marked, update underlying
  *			storage.
  * @set_bytes_per_datum:set number of bytes per datum
- * @get_length:		get number of datums in buffer
  * @set_length:		set number of datums in buffer
  * @release:		called when the last reference to the buffer is dropped,
  *			should free all resources allocated by the buffer.
···
 	int (*request_update)(struct iio_buffer *buffer);
 
 	int (*set_bytes_per_datum)(struct iio_buffer *buffer, size_t bpd);
-	int (*get_length)(struct iio_buffer *buffer);
 	int (*set_length)(struct iio_buffer *buffer, int length);
 
 	void (*release)(struct iio_buffer *buffer);