diff mbox series

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

Message ID 20210112132339.5621-14-ezequiel@collabora.com
State Superseded
Headers show
Series V4L2 Async notifier API cleanup | expand

Commit Message

Ezequiel Garcia Jan. 12, 2021, 1:23 p.m. UTC
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@collabora.com>
---
 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(-)

Comments

Laurent Pinchart Jan. 14, 2021, 2:27 a.m. UTC | #1
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@collabora.com>

> ---

>  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@ideasonboard.com>


> 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
Ezequiel Garcia Jan. 14, 2021, 1:47 p.m. UTC | #2
Hi Laurent,

On Thu, 2021-01-14 at 04:27 +0200, Laurent Pinchart wrote:
> 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@collabora.com>

> > ---

> >  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,

> 


Yeah, I thought about that, precisely to avoid the export and disallow
any future users of v4l2_async_notifier_add_subdev.

The impact of that is that we'd kill V4L2_FWNODE, increasing the
size of videodev.ko, by a small fraction.

Perhaps this is justified? I'm sure all the use-cases for this type
of hardware won't care for 20 KiB more or less in the kernel payload.

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

> 

> > 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);

> >  

> >  /**

> 


Thanks,
Ezequiel
Laurent Pinchart Jan. 15, 2021, 6:57 a.m. UTC | #3
Hi Ezequiel,

On Thu, Jan 14, 2021 at 10:47:08AM -0300, Ezequiel Garcia wrote:
> On Thu, 2021-01-14 at 04:27 +0200, Laurent Pinchart wrote:

> > 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@collabora.com>

> > > ---

> > >  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,

> > 

> 

> Yeah, I thought about that, precisely to avoid the export and disallow

> any future users of v4l2_async_notifier_add_subdev.

> 

> The impact of that is that we'd kill V4L2_FWNODE, increasing the

> size of videodev.ko, by a small fraction.


We don't have to drop V4L2_FWNODE, we can still make v4l2-async.o
conditional, even if it's included in videodev.ko.

> Perhaps this is justified? I'm sure all the use-cases for this type

> of hardware won't care for 20 KiB more or less in the kernel payload.

> 

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

> > 

> > > 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
diff mbox series

Patch

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)
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);
 
 /**