[PATCH 03/13] rapidio: fix return value description for dma_prep functions

[Alexandre Bounine <alexandre.bounine@idt.com>]

Update return value description for rio_dma_prep_... functions to include
error-valued pointer that can be returned by HW mport device drivers.
Return values from these functions must be checked using IS_ERR_OR_NULL
macro.

This patch is applicable to kernel versions starting from v4.6-rc1.

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Andre van Herk <andre.van.herk@prodrive-technologies.com>
Cc: Barry Wood <barry.wood@idt.com>
Cc: linux-kernel@vger.kernel.org
---
 drivers/rapidio/rio.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/rapidio/rio.c b/drivers/rapidio/rio.c
index 0dcaa66..8408029 100644
--- a/drivers/rapidio/rio.c
+++ b/drivers/rapidio/rio.c
@@ -1848,7 +1848,9 @@ EXPORT_SYMBOL_GPL(rio_release_dma);
  * Initializes RapidIO capable DMA channel for the specified data transfer.
  * Uses DMA channel private extension to pass information related to remote
  * target RIO device.
- * Returns pointer to DMA transaction descriptor or NULL if failed.
+ *
+ * Returns: pointer to DMA transaction descriptor if successful,
+ *          error-valued pointer or NULL if failed.
  */
 struct dma_async_tx_descriptor *rio_dma_prep_xfer(struct dma_chan *dchan,
 	u16 destid, struct rio_dma_data *data,
@@ -1883,7 +1885,9 @@ EXPORT_SYMBOL_GPL(rio_dma_prep_xfer);
  * Initializes RapidIO capable DMA channel for the specified data transfer.
  * Uses DMA channel private extension to pass information related to remote
  * target RIO device.
- * Returns pointer to DMA transaction descriptor or NULL if failed.
+ *
+ * Returns: pointer to DMA transaction descriptor if successful,
+ *          error-valued pointer or NULL if failed.
  */
 struct dma_async_tx_descriptor *rio_dma_prep_slave_sg(struct rio_dev *rdev,
 	struct dma_chan *dchan, struct rio_dma_data *data,
-- 
1.7.8.4