Some users of DRM bridges may need to execute specific code just before
deallocation.

As of now the only known user would be KUnit tests.

Suggested-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

---

This patch is new in v8. The .destroy callback had appeared in v5 as well
[5], but as part of a larger patch and for different reason that do not
apply anymore.

[5] https://lore.kernel.org/all/20241231-hotplug-drm-bridge-v5-3-173065a1ece1@bootlin.com/#t
---
 drivers/gpu/drm/drm_bridge.c |  2 ++
 include/drm/drm_bridge.h     | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index b4c89ec01998b849018ce031c7cd84614e65e710..6185cb29fe3162264f0912c09c205fb467975dee 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -203,6 +203,8 @@ static void __drm_bridge_free(struct kref *kref)
 {
 	struct drm_bridge *bridge = container_of(kref, struct drm_bridge, refcount);
 
+	if (bridge->funcs->destroy)
+		bridge->funcs->destroy(bridge);
 	kfree(bridge->container);
 }
 
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 4e418a29a9ff9d014d6ac0910a5d9bcf7118195e..3ccd493faa580845c2ed1166f398eca27b464261 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -86,6 +86,16 @@ struct drm_bridge_funcs {
 	 */
 	void (*detach)(struct drm_bridge *bridge);
 
+	/**
+	 * @destroy:
+	 *
+	 * This callback is invoked when the bridge is about to be
+	 * deallocated.
+	 *
+	 * The @destroy callback is optional.
+	 */
+	void (*destroy)(struct drm_bridge *bridge);
+
 	/**
 	 * @mode_valid:
 	 *

-- 
2.49.0

On Fri, May 16, 2025 at 06:48:38PM +0200, Luca Ceresoli wrote:
> Some users of DRM bridges may need to execute specific code just before
> deallocation.
> 
> As of now the only known user would be KUnit tests.
> 
> Suggested-by: Maxime Ripard <mripard@kernel.org>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> 
> ---
> 
> This patch is new in v8. The .destroy callback had appeared in v5 as well
> [5], but as part of a larger patch and for different reason that do not
> apply anymore.
> 
> [5] https://lore.kernel.org/all/20241231-hotplug-drm-bridge-v5-3-173065a1ece1@bootlin.com/#t
> ---
>  drivers/gpu/drm/drm_bridge.c |  2 ++
>  include/drm/drm_bridge.h     | 10 ++++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index b4c89ec01998b849018ce031c7cd84614e65e710..6185cb29fe3162264f0912c09c205fb467975dee 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -203,6 +203,8 @@ static void __drm_bridge_free(struct kref *kref)
>  {
>  	struct drm_bridge *bridge = container_of(kref, struct drm_bridge, refcount);
>  
> +	if (bridge->funcs->destroy)
> +		bridge->funcs->destroy(bridge);
>  	kfree(bridge->container);
>  }
>  
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 4e418a29a9ff9d014d6ac0910a5d9bcf7118195e..3ccd493faa580845c2ed1166f398eca27b464261 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -86,6 +86,16 @@ struct drm_bridge_funcs {
>  	 */
>  	void (*detach)(struct drm_bridge *bridge);
>  
> +	/**
> +	 * @destroy:
> +	 *
> +	 * This callback is invoked when the bridge is about to be
> +	 * deallocated.
> +	 *
> +	 * The @destroy callback is optional.
> +	 */
> +	void (*destroy)(struct drm_bridge *bridge);
> +

destroy is before detach in alphabetical order, but otherwise it looks
good to me.

Once fixed,
Acked-by: Maxime Ripard <mripard@kernel.org>

Maxime

Hi Maxime,

On Thu, 22 May 2025 17:43:37 +0200
Maxime Ripard <mripard@kernel.org> wrote:

> On Fri, May 16, 2025 at 06:48:38PM +0200, Luca Ceresoli wrote:
> > Some users of DRM bridges may need to execute specific code just before
> > deallocation.
> > 
> > As of now the only known user would be KUnit tests.
> > 
> > Suggested-by: Maxime Ripard <mripard@kernel.org>
> > Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> > 
> > ---
> > 
> > This patch is new in v8. The .destroy callback had appeared in v5 as well
> > [5], but as part of a larger patch and for different reason that do not
> > apply anymore.
> > 
> > [5] https://lore.kernel.org/all/20241231-hotplug-drm-bridge-v5-3-173065a1ece1@bootlin.com/#t
> > ---
> >  drivers/gpu/drm/drm_bridge.c |  2 ++
> >  include/drm/drm_bridge.h     | 10 ++++++++++
> >  2 files changed, 12 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index b4c89ec01998b849018ce031c7cd84614e65e710..6185cb29fe3162264f0912c09c205fb467975dee 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -203,6 +203,8 @@ static void __drm_bridge_free(struct kref *kref)
> >  {
> >  	struct drm_bridge *bridge = container_of(kref, struct drm_bridge, refcount);
> >  
> > +	if (bridge->funcs->destroy)
> > +		bridge->funcs->destroy(bridge);
> >  	kfree(bridge->container);
> >  }
> >  
> > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > index 4e418a29a9ff9d014d6ac0910a5d9bcf7118195e..3ccd493faa580845c2ed1166f398eca27b464261 100644
> > --- a/include/drm/drm_bridge.h
> > +++ b/include/drm/drm_bridge.h
> > @@ -86,6 +86,16 @@ struct drm_bridge_funcs {
> >  	 */
> >  	void (*detach)(struct drm_bridge *bridge);
> >  
> > +	/**
> > +	 * @destroy:
> > +	 *
> > +	 * This callback is invoked when the bridge is about to be
> > +	 * deallocated.
> > +	 *
> > +	 * The @destroy callback is optional.
> > +	 */
> > +	void (*destroy)(struct drm_bridge *bridge);
> > +  
> 
> destroy is before detach in alphabetical order, but otherwise it looks
> good to me.

I saw the struct is not alpha-ordered right now, so I did not get it
should be, and it looked like keeping .attach and .detach nearby would
be good.

> Once fixed,
> Acked-by: Maxime Ripard <mripard@kernel.org>

OK, will send new iteration with .destroy before .detach, thanks for
the review.

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com