[PATCH] vu_common: Clarify prototype of vu_collect()

[PATCH] vu_common: Clarify prototype of vu_collect()

[Stefano Brivio]

The last argument of vu_collect() can't exceed @size, but this isn't
documented and it wasn't obvious to me, to the point that I actually
proposed a change to "fix" callers so that they wouldn't overrun input
buffers.

Rename @frame_size to @collected, and clarify that it can only be up
to @size bytes.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 vu_common.c | 8 ++++----
 vu_common.h | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/vu_common.c b/vu_common.c
index b13b7c3..ce61fa6 100644
--- a/vu_common.c
+++ b/vu_common.c
@@ -76,13 +76,13 @@ void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov, int elem_cnt
  * 			in the in_sg array.
  * @max_elem:		Number of virtqueue elements in the array
  * @size:		Maximum size of the data in the frame
- * @frame_size:		The total size of the buffers (output)
+ * @collected:		Collected buffer length, up to @size, set on return
  *
  * Return: number of elements used to contain the frame
  */
 int vu_collect(const struct vu_dev *vdev, struct vu_virtq *vq,
 	       struct vu_virtq_element *elem, int max_elem,
-	       size_t size, size_t *frame_size)
+	       size_t size, size_t *collected)
 {
 	size_t current_size = 0;
 	int elem_cnt = 0;
@@ -113,8 +113,8 @@ int vu_collect(const struct vu_dev *vdev, struct vu_virtq *vq,
 			break;
 	}
 
-	if (frame_size)
-		*frame_size = current_size;
+	if (collected)
+		*collected = current_size;
 
 	return elem_cnt;
 }
diff --git a/vu_common.h b/vu_common.h
index f538f23..c0883b2 100644
--- a/vu_common.h
+++ b/vu_common.h
@@ -48,7 +48,7 @@ void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov,
 		  int elem_cnt);
 int vu_collect(const struct vu_dev *vdev, struct vu_virtq *vq,
 	       struct vu_virtq_element *elem, int max_elem, size_t size,
-	       size_t *frame_size);
+	       size_t *collected);
 void vu_set_vnethdr(const struct vu_dev *vdev,
 		    struct virtio_net_hdr_mrg_rxbuf *vnethdr,
                     int num_buffers);
-- 
2.43.0

Re: [PATCH] vu_common: Clarify prototype of vu_collect()

[David Gibson]

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On Fri, Dec 05, 2025 at 01:51:05AM +0100, Stefano Brivio wrote:
> The last argument of vu_collect() can't exceed @size, but this isn't
> documented and it wasn't obvious to me, to the point that I actually
> proposed a change to "fix" callers so that they wouldn't overrun input
> buffers.
> 
> Rename @frame_size to @collected, and clarify that it can only be up
> to @size bytes.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  vu_common.c | 8 ++++----
>  vu_common.h | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/vu_common.c b/vu_common.c
> index b13b7c3..ce61fa6 100644
> --- a/vu_common.c
> +++ b/vu_common.c
> @@ -76,13 +76,13 @@ void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov, int elem_cnt
>   * 			in the in_sg array.
>   * @max_elem:		Number of virtqueue elements in the array
>   * @size:		Maximum size of the data in the frame
> - * @frame_size:		The total size of the buffers (output)
> + * @collected:		Collected buffer length, up to @size, set on return
>   *
>   * Return: number of elements used to contain the frame
>   */
>  int vu_collect(const struct vu_dev *vdev, struct vu_virtq *vq,
>  	       struct vu_virtq_element *elem, int max_elem,
> -	       size_t size, size_t *frame_size)
> +	       size_t size, size_t *collected)
>  {
>  	size_t current_size = 0;
>  	int elem_cnt = 0;
> @@ -113,8 +113,8 @@ int vu_collect(const struct vu_dev *vdev, struct vu_virtq *vq,
>  			break;
>  	}
>  
> -	if (frame_size)
> -		*frame_size = current_size;
> +	if (collected)
> +		*collected = current_size;
>  
>  	return elem_cnt;
>  }
> diff --git a/vu_common.h b/vu_common.h
> index f538f23..c0883b2 100644
> --- a/vu_common.h
> +++ b/vu_common.h
> @@ -48,7 +48,7 @@ void vu_init_elem(struct vu_virtq_element *elem, struct iovec *iov,
>  		  int elem_cnt);
>  int vu_collect(const struct vu_dev *vdev, struct vu_virtq *vq,
>  	       struct vu_virtq_element *elem, int max_elem, size_t size,
> -	       size_t *frame_size);
> +	       size_t *collected);
>  void vu_set_vnethdr(const struct vu_dev *vdev,
>  		    struct virtio_net_hdr_mrg_rxbuf *vnethdr,
>                      int num_buffers);
> -- 
> 2.43.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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