iio: buffer: split buffer sysfs creation to take buffer as primary arg

Currently the iio_buffer_{alloc,free}_sysfs_and_mask() take 'indio_dev' as
primary argument. This change splits the main logic into a private function
that takes an IIO buffer as primary argument.

That way, the functions can be extended to configure the sysfs for multiple
buffers.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200917125951.861-1-alexandru.ardelean@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-buffer.c

@@ -1264,26 +1264,14 @@ static struct attribute *iio_buffer_attrs[] = {
 	&dev_attr_data_available.attr,
 };
 
-int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
+static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
+					     struct iio_dev *indio_dev)
 {
 	struct iio_dev_attr *p;
 	struct attribute **attr;
-	struct iio_buffer *buffer = indio_dev->buffer;
 	int ret, i, attrn, attrcount;
 	const struct iio_chan_spec *channels;
 
-	channels = indio_dev->channels;
-	if (channels) {
-		int ml = indio_dev->masklength;
-
-		for (i = 0; i < indio_dev->num_channels; i++)
-			ml = max(ml, channels[i].scan_index + 1);
-		indio_dev->masklength = ml;
-	}
-
-	if (!buffer)
-		return 0;
-
 	attrcount = 0;
 	if (buffer->attrs) {
 		while (buffer->attrs[attrcount] != NULL)
@@ -1367,19 +1355,45 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
 	return ret;
 }
 
-void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
+int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
 {
 	struct iio_buffer *buffer = indio_dev->buffer;
+	const struct iio_chan_spec *channels;
+	int i;
+
+	channels = indio_dev->channels;
+	if (channels) {
+		int ml = indio_dev->masklength;
+
+		for (i = 0; i < indio_dev->num_channels; i++)
+			ml = max(ml, channels[i].scan_index + 1);
+		indio_dev->masklength = ml;
+	}
 
 	if (!buffer)
-		return;
+		return 0;
+
+	return __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev);
+}
 
+static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer)
+{
 	bitmap_free(buffer->scan_mask);
 	kfree(buffer->buffer_group.attrs);
 	kfree(buffer->scan_el_group.attrs);
 	iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
 }
 
+void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
+{
+	struct iio_buffer *buffer = indio_dev->buffer;
+
+	if (!buffer)
+		return;
+
+	__iio_buffer_free_sysfs_and_mask(buffer);
+}
+
 /**
  * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
  * @indio_dev: the iio device