Re: [PATCH 13/13] media: v4l2-async: Discourage use of v4l2_async_notifier_add_subdev

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Hi Ezequiel,

Thank you for the patch.

On Tue, Jan 12, 2021 at 10:23:39AM -0300, Ezequiel Garcia wrote:
> Most -if not all- use-cases are expected to be covered by one of:
> v4l2_async_notifier_add_fwnode_subdev,
> v4l2_async_notifier_add_fwnode_remote_subdev,
> v4l2_async_notifier_add_i2c_subdev or
> v4l2_async_notifier_add_devname_subdev.
> 
> We'd like to discourage drivers from using v4l2_async_notifier_add_subdev,
> so rename it as __v4l2_async_notifier_add_subdev. This is
> typically a good hint for drivers to avoid using the function.
> 
> Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
> ---
>  drivers/media/v4l2-core/v4l2-async.c  | 10 +++++-----
>  drivers/media/v4l2-core/v4l2-fwnode.c |  2 +-
>  include/media/v4l2-async.h            | 10 ++++++++--
>  3 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index b325bacddff4..e8e690280922 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -630,7 +630,7 @@ void v4l2_async_notifier_cleanup(struct v4l2_async_notifier *notifier)
>  }
>  EXPORT_SYMBOL_GPL(v4l2_async_notifier_cleanup);
>  
> -int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
> +int __v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
>  				   struct v4l2_async_subdev *asd)
>  {
>  	int ret;
> @@ -647,7 +647,7 @@ int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
>  	mutex_unlock(&list_lock);
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(v4l2_async_notifier_add_subdev);
> +EXPORT_SYMBOL_GPL(__v4l2_async_notifier_add_subdev);
>  
>  struct v4l2_async_subdev *
>  v4l2_async_notifier_add_fwnode_subdev(struct v4l2_async_notifier *notifier,
> @@ -664,7 +664,7 @@ v4l2_async_notifier_add_fwnode_subdev(struct v4l2_async_notifier *notifier,
>  	asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
>  	asd->match.fwnode = fwnode_handle_get(fwnode);
>  
> -	ret = v4l2_async_notifier_add_subdev(notifier, asd);
> +	ret = __v4l2_async_notifier_add_subdev(notifier, asd);
>  	if (ret) {
>  		fwnode_handle_put(fwnode);
>  		kfree(asd);
> @@ -714,7 +714,7 @@ v4l2_async_notifier_add_i2c_subdev(struct v4l2_async_notifier *notifier,
>  	asd->match.i2c.adapter_id = adapter_id;
>  	asd->match.i2c.address = address;
>  
> -	ret = v4l2_async_notifier_add_subdev(notifier, asd);
> +	ret = __v4l2_async_notifier_add_subdev(notifier, asd);
>  	if (ret) {
>  		kfree(asd);
>  		return ERR_PTR(ret);
> @@ -739,7 +739,7 @@ v4l2_async_notifier_add_devname_subdev(struct v4l2_async_notifier *notifier,
>  	asd->match_type = V4L2_ASYNC_MATCH_DEVNAME;
>  	asd->match.device_name = device_name;
>  
> -	ret = v4l2_async_notifier_add_subdev(notifier, asd);
> +	ret = __v4l2_async_notifier_add_subdev(notifier, asd);
>  	if (ret) {
>  		kfree(asd);
>  		return ERR_PTR(ret);
> diff --git a/drivers/media/v4l2-core/v4l2-fwnode.c b/drivers/media/v4l2-core/v4l2-fwnode.c
> index 5353e37eb950..919fde20032e 100644
> --- a/drivers/media/v4l2-core/v4l2-fwnode.c
> +++ b/drivers/media/v4l2-core/v4l2-fwnode.c
> @@ -833,7 +833,7 @@ v4l2_async_notifier_fwnode_parse_endpoint(struct device *dev,
>  	if (ret < 0)
>  		goto out_err;
>  
> -	ret = v4l2_async_notifier_add_subdev(notifier, asd);
> +	ret = __v4l2_async_notifier_add_subdev(notifier, asd);
>  	if (ret < 0) {
>  		/* not an error if asd already exists */
>  		if (ret == -EEXIST)

I wonder if v4l2-fwnode should be moved to videodev-objs in the
Makefile, we could then avoid exporting
__v4l2_async_notifier_add_subdev(). This doesn't need to be fixed here,

Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>

> diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> index 1278f98355a7..9cf83f1ecca6 100644
> --- a/include/media/v4l2-async.h
> +++ b/include/media/v4l2-async.h
> @@ -161,17 +161,23 @@ void v4l2_async_debug_init(struct dentry *debugfs_dir);
>  void v4l2_async_notifier_init(struct v4l2_async_notifier *notifier);
>  
>  /**
> - * v4l2_async_notifier_add_subdev - Add an async subdev to the
> + * __v4l2_async_notifier_add_subdev - Add an async subdev to the
>   *				notifier's master asd list.
>   *
>   * @notifier: pointer to &struct v4l2_async_notifier
>   * @asd: pointer to &struct v4l2_async_subdev
>   *
> + * \warning: Drivers should avoid using this function and instead use one of:
> + * @v4l2_async_notifier_add_fwnode_subdev,
> + * @v4l2_async_notifier_add_fwnode_remote_subdev,
> + * @v4l2_async_notifier_add_i2c_subdev or
> + * @v4l2_async_notifier_add_devname_subdev.
> + *
>   * Call this function before registering a notifier to link the provided @asd to
>   * the notifiers master @asd_list. The @asd must be allocated with k*alloc() as
>   * it will be freed by the framework when the notifier is destroyed.
>   */
> -int v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
> +int __v4l2_async_notifier_add_subdev(struct v4l2_async_notifier *notifier,
>  				   struct v4l2_async_subdev *asd);
>  
>  /**

-- 
Regards,

Laurent Pinchart



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