linux-kernel - Re: [PATCH v2] virtio: Update kerneldoc in drivers/virtio/virtio_dma

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Message-ID: <20250716095046-mutt-send-email-mst@kernel.org>
Date: Wed, 16 Jul 2025 09:56:46 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: jiang.peng9@....com.cn
Cc: jasowang@...hat.com, krzk@...nel.org, xuanzhuo@...ux.alibaba.com,
	eperezma@...hat.com, sumit.semwal@...aro.org,
	christian.koenig@....com, virtualization@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, xu.xin16@....com.cn,
	yang.yang29@....com.cn
Subject: Re: [PATCH v2] virtio: Update kerneldoc in
 drivers/virtio/virtio_dma_buf.c

On Sat, Jul 05, 2025 at 10:58:03AM +0800, jiang.peng9@....com.cn wrote:
> From: Peng Jiang <jiang.peng9@....com.cn>
> 
> Fix kernel-doc descriptions in virtio_dma_buf.c to fix W=1 warnings:
> 
> drivers/virtio/virtio_dma_buf.c:41 function parameter 'dma_buf' not described in 'virtio_dma_buf_attach'
> drivers/virtio/virtio_dma_buf.c:41 function parameter 'attach' not described in 'virtio_dma_buf_attach'
> 
> Signed-off-by: Peng Jiang <jiang.peng9@....com.cn>


The extra documentation unfortunately just mechanically repeats what the
code does. Code comments should explain the reasoning behind the code,
instead.


> ---
>  drivers/virtio/virtio_dma_buf.c | 30 +++++++++++++++++++++++++-----
>  1 file changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_dma_buf.c b/drivers/virtio/virtio_dma_buf.c
> index 3fe1d03b0645..0b39b1b209ee 100644
> --- a/drivers/virtio/virtio_dma_buf.c
> +++ b/drivers/virtio/virtio_dma_buf.c
> @@ -9,13 +9,20 @@
>  #include <linux/virtio_dma_buf.h>
> 
>  /**
> - * virtio_dma_buf_export - Creates a new dma-buf for a virtio exported object
> + * virtio_dma_buf_export() - Creates a new dma-buf for a virtio exported object

virtio core uses the form without () consistently, everywhere.



>   * @exp_info: [in] see dma_buf_export(). ops MUST refer to a dma_buf_ops
>   *     struct embedded in a virtio_dma_buf_ops.
>   *
>   * This wraps dma_buf_export() to allow virtio drivers to create a dma-buf
>   * for an virtio exported object that can be queried by other virtio drivers
>   * for the object's UUID.
> + *
> + * Returns:
> + *   - Valid struct dma_buf pointer on success
> + *   - ERR_PTR(-EINVAL) if:
> + *     - exp_info->ops is NULL
> + *     - attach callback isn't virtio_dma_buf_attach()
> + *     - virtio_ops->get_uuid() is not implemented

Too verbose, no one will rememeber to update this when changing code.
Just 
	Returns the dma_buf or ERR_PTR

is enough.


>   */
>  struct dma_buf *virtio_dma_buf_export
>         (const struct dma_buf_export_info *exp_info)
> @@ -35,7 +42,16 @@ struct dma_buf *virtio_dma_buf_export
>  EXPORT_SYMBOL(virtio_dma_buf_export);
> 
>  /**
> - * virtio_dma_buf_attach - mandatory attach callback for virtio dma-bufs
> + * virtio_dma_buf_attach() - Mandatory attach callback for virtio dma-bufs
> + * @dma_buf: Pointer to the shared dma-buf structure
> + * @attach: Pointer to the newly created attachment metadata
> + *
> + * Implements the standard dma-buf attach operation for virtio devices.
> + * Retrieves virtio-specific operations through container_of macro,
> + * then invokes device-specific attach callback if present.
> + * This enables virtio devices to participate in dma-buf sharing.
> + *

Same thing pls do not repeat all of code.

> + * Return: 0 on success, error code on failure

we say "Returns zero or a negative error" elsewhere. seems clearer.

>   */
>  int virtio_dma_buf_attach(struct dma_buf *dma_buf,
>                           struct dma_buf_attachment *attach)
> @@ -55,8 +71,12 @@ int virtio_dma_buf_attach(struct dma_buf *dma_buf,
>  EXPORT_SYMBOL(virtio_dma_buf_attach);
> 
>  /**
> - * is_virtio_dma_buf - returns true if the given dma-buf is a virtio dma-buf
> - * @dma_buf: buffer to query
> + * is_virtio_dma_buf() - Check if a dma-buf was created by virtio DMA framework
> + * @dma_buf: [in] buffer to query
> + *
> + * Returns:
> + *   - true  if the dma-buf uses virtio_dma_buf_attach() as its attach callback
> + *   - false otherwise


one is return one is returns ... no consistency.

>   */
>  bool is_virtio_dma_buf(struct dma_buf *dma_buf)
>  {
> @@ -65,7 +85,7 @@ bool is_virtio_dma_buf(struct dma_buf *dma_buf)
>  EXPORT_SYMBOL(is_virtio_dma_buf);
> 
>  /**
> - * virtio_dma_buf_get_uuid - gets a virtio dma-buf's exported object's uuid
> + * virtio_dma_buf_get_uuid() - gets a virtio dma-buf's exported object's uuid
>   * @dma_buf: [in] buffer to query
>   * @uuid: [out] the uuid
>   *
> -- 
> 2.25.1