[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 documents an -EBUSY return
for the case where 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 updated the description paragraph above,
but left the return value description behind.

The only failure the function can report now comes from strndup_user(),
propagated via PTR_ERR(); every other path returns 0. Document that
instead, using a Return: section so kernel-doc picks it up.

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>
---
Changes in v2:
 - Use a "Return:" section so kernel-doc actually parses the return
   value description; scripts/kernel-doc -none -Wall reported "No
   description found for return value of 'dma_buf_set_name'" before
   this change and is quiet after it.
 - Reference the commit that made the -EBUSY text stale, and add a
   Fixes: tag for it.
 - Resend to the dma-buf maintainers and dri-devel; v1 only reached
   linux-media, where it was marked "Not Applicable".

v1: https://lore.kernel.org/linux-media/20260730003153.4030818-1-alan.tseng.cs@xxxxxxxxx/

 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