iio: make use of devm_iio_kfifo_buffer_setup() helper

All drivers that already call devm_iio_kfifo_allocate() &
iio_device_attach_buffer() are simple to convert to
iio_device_attach_kfifo_buffer() in a single go.

This change does that; the unwind order is preserved.
What is important, is that the devm_iio_kfifo_buffer_setup() be called
after the indio_dev->modes is assigned, to make sure that
INDIO_BUFFER_SOFTWARE flag is set and not overridden by the assignment to
indio_dev->modes.

Also, the INDIO_BUFFER_SOFTWARE has been removed from the assignments of
'indio_dev->modes' because it is set by devm_iio_kfifo_buffer_setup().

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Matt Ranostay <matt.ranostay@konsulko.com>x
Link: https://lore.kernel.org/r/20210215104043.91251-4-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
diff --git a/drivers/iio/light/apds9960.c b/drivers/iio/light/apds9960.c
index df06478..4141c0f 100644
--- a/drivers/iio/light/apds9960.c
+++ b/drivers/iio/light/apds9960.c
@@ -988,7 +988,6 @@ static int apds9960_probe(struct i2c_client *client,
 			  const struct i2c_device_id *id)
 {
 	struct apds9960_data *data;
-	struct iio_buffer *buffer;
 	struct iio_dev *indio_dev;
 	int ret;
 
@@ -996,19 +995,18 @@ static int apds9960_probe(struct i2c_client *client,
 	if (!indio_dev)
 		return -ENOMEM;
 
-	buffer = devm_iio_kfifo_allocate(&client->dev);
-	if (!buffer)
-		return -ENOMEM;
-
-	iio_device_attach_buffer(indio_dev, buffer);
-
 	indio_dev->info = &apds9960_info;
 	indio_dev->name = APDS9960_DRV_NAME;
 	indio_dev->channels = apds9960_channels;
 	indio_dev->num_channels = ARRAY_SIZE(apds9960_channels);
 	indio_dev->available_scan_masks = apds9960_scan_masks;
-	indio_dev->modes = (INDIO_BUFFER_SOFTWARE | INDIO_DIRECT_MODE);
-	indio_dev->setup_ops = &apds9960_buffer_setup_ops;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = devm_iio_kfifo_buffer_setup(&client->dev, indio_dev,
+					  INDIO_BUFFER_SOFTWARE,
+					  &apds9960_buffer_setup_ops);
+	if (ret)
+		return ret;
 
 	data = iio_priv(indio_dev);
 	i2c_set_clientdata(client, indio_dev);