Hi Luca,
On Tue, Mar 24, 2026 at 10:08:49AM +0100, Luca Ceresoli wrote:
> drm_bridge_get and drm_bridge_put() do nothing when they are passed a NULL
> pointer, and they do so since their initial addition in commit 30d1b37d4c02
> ("drm/bridge: add support for refcounting").
>
> This allows simpler code in various places when using these
> functions. However it's not documented, so it's not clear whether it is
> part of the API "contract" or just a current implementation detail that
> might change in the future.
>
> There is no visible reason to remove this NULL check, so document it,
> making it part of the contract, letting users count on it.
>
> Signed-off-by: Luca Ceresoli <[email protected]>
> ---
> Historical note: I thought this was documented from the beginning and
> realized it's not the case when someone proposed adding a 'if (bridge)
> drm_bridge_put(bridge)' to a driver [0]. Let's fix it now.
>
> [0] https://lore.kernel.org/lkml/[email protected]/
> ---
> drivers/gpu/drm/drm_bridge.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 3b165a0d1e77..3108249a63cd 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -282,7 +282,7 @@ static void __drm_bridge_free(struct kref *kref)
>
> /**
> * drm_bridge_get - Acquire a bridge reference
> - * @bridge: DRM bridge
> + * @bridge: DRM bridge; if NULL this function does nothing
> *
> * This function increments the bridge's refcount.
> *
> @@ -300,7 +300,7 @@ EXPORT_SYMBOL(drm_bridge_get);
>
> /**
> * drm_bridge_put - Release a bridge reference
> - * @bridge: DRM bridge
> + * @bridge: DRM bridge; if NULL this function does nothing
So, we can drop the if(_T) check for cleanup action, right?
DEFINE_FREE(drm_bridge_put, struct drm_bridge *, if (_T) drm_bridge_put(_T))
Reviewed-by: Liu Ying <[email protected]>
> *
> * This function decrements the bridge's reference count and frees the
> * object if the reference count drops to zero.
>
> ---
> base-commit: a50007089e078a1b7a826559a02277b1601ee189
> change-id: 20260129-drm-bridge-alloc-getput-document-null-check-a551e64b8fc1
>
> Best regards,
--
Regards,
Liu Ying
