[PATCH v2] dma-buf: fix stale return value documentation for dma_buf_set_name()

[Hung-Chun Tseng]

The kernel-doc for dma_buf_set_name() still promises that the function
returns -EBUSY when the dma-buf is already attached to devices:

  Returns 0 on success. If the dma-buf buffer is already attached to
  devices, return -EBUSY.

That has not been true since commit e73c317efbf9 ("dma-buf: remove
restriction of IOCTL:DMA_BUF_SET_NAME"), which dropped the
dma_resv_lock() and the !list_empty(&dmabuf->attachments) check that
produced -EBUSY. That commit rewrote the first paragraph of the comment
to match, but left the return value description behind.

The only failure the function can report now comes from strndup_user(),
which is propagated via PTR_ERR(); every other path returns 0. Describe
that instead, using a Return: section so kernel-doc picks it up:
scripts/kernel-doc -none -Wall drivers/dma-buf/dma-buf.c reports "No
description found for return value of 'dma_buf_set_name'" before this
change and is quiet after it.

No functional change.

Fixes: e73c317efbf9 ("dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME")
Signed-off-by: Hung-Chun Tseng <alan.tseng.cs@xxxxxxxxx>
---
v1 was sent on 2026-07-29 and did not get any review comments.

v1 -> v2:
 - Use a "Return:" section instead of a plain "Returns ..." sentence, so
   kernel-doc actually parses the description (fixes a -Wall warning).
 - Add a Fixes: tag pointing at the commit that removed the -EBUSY path.
 - Widen the Cc list to the dma-buf maintainers, linux-media and
   dri-devel; v1 only went to LKML, which is most likely why it was
   missed.

 drivers/dma-buf/dma-buf.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index d504c636dc..6ee3c254d7 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -413,9 +413,8 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
  * @buf:    [in]     A piece of userspace memory that contains the name of
  *                   the dma-buf.
  *
- * Returns 0 on success. If the dma-buf buffer is already attached to
- * devices, return -EBUSY.
- *
+ * Return: 0 on success, or a negative error code from strndup_user() on
+ * failure.
  */
 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
 {
-- 
2.43.0