Re: [PATCH v4 02/11] drm/bridge: add of_drm_get_bridge_by_endpoint()

Laurent Pinchart
2026-05-04T14:55:40Z

On Mon, May 04, 2026 at 12:45:05PM +0200, Luca Ceresoli wrote:
> drm_of_find_panel_or_bridge() is widely used, but many callers pass NULL
> into the @panel or the @bridge arguments, thus making a very partial usage
> of this rather complex function.
>
> Besides, the bridge returned in @bridge is not refcounted, thus making this
> API unsafe when DRM bridge hotplug will be introduced.
>
> Solve both issues for the cases of calls to drm_of_find_panel_or_bridge()
> with a NULL @panel pointer by adding a new function that only looks for
> bridges (and is thus much simpler) and increments the refcount of the
> returned bridge.
>
> The new function is identical to drm_of_find_panel_or_bridge() except it:
>
> - handles bridge refcounting: uses of_drm_find_and_get_bridge() instead of
> of_drm_find_bridge() internally to return a refcounted bridge
> - is simpler to use: just takes no @panel parameter, returns the pointer
> in the return value instead of a double pointer argument
> - has a simpler implementation: it is equal to
> drm_of_find_panel_or_bridge() after removing the code that becomes dead
> when @panel == NULL
>
> Also add this function to drm_bridge.c and not drm_of.c because it returns
> bridges only.
>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> ---
> Changes in v4:
> - update function declaration in non-OF case
>
> Changes in v2:
> - return the bridge in the return value, not a double pointer
> ---
> drivers/gpu/drm/drm_bridge.c | 41 +++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_bridge.h | 7 +++++++
> 2 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 6fb71de6d22a..01f9e0426648 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -1582,6 +1582,47 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np)
> return bridge;
> }
> EXPORT_SYMBOL(of_drm_find_bridge);
> +
> +/**
> + * of_drm_get_bridge_by_endpoint - return DRM bridge connected to a port/endpoint
> + * @np: device tree node containing output ports
> + * @port: port in the device tree node, or -1 for the first port found
> + * @endpoint: endpoint in the device tree node, or -1 for the first endpoint found
> + *
> + * Given a DT node's port and endpoint number, find the connected node and
> + * return the associated drm_bridge device.
> + *
> + * The refcount of the returned bridge is incremented. Use drm_bridge_put()
> + * when done with it.
> + *
> + * Returns a pointer to the connected drm_bridge, or a negative error on failure
> + */
> +struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np,
> + int port, int endpoint)
> +{
> + struct drm_bridge *bridge;
> +
> + /*
> + * of_graph_get_remote_node() produces a noisy error message if port
> + * node isn't found and the absence of the port is a legit case here,
> + * so at first we silently check whether graph presents in the

s/graph presents/graph is present/

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

> + * device-tree node.
> + */
> + if (!of_graph_is_present(np))
> + return ERR_PTR(-ENODEV);
> +
> + struct device_node *remote __free(device_node) =
> + of_graph_get_remote_node(np, port, endpoint);
> + if (!remote)
> + return ERR_PTR(-ENODEV);
> +
> + bridge = of_drm_find_and_get_bridge(remote);
> + if (!bridge)
> + return ERR_PTR(-EPROBE_DEFER);
> +
> + return bridge;
> +}
> +EXPORT_SYMBOL_GPL(of_drm_get_bridge_by_endpoint);
> #endif
>
> /**
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index d6cd0f5af045..31e11a360c42 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -1327,6 +1327,8 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> #ifdef CONFIG_OF
> struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np);
> struct drm_bridge *of_drm_find_bridge(struct device_node *np);
> +struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np,
> + int port, int endpoint);
> #else
> static inline struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np)
> {
> @@ -1336,6 +1338,11 @@ static inline struct drm_bridge *of_drm_find_bridge(struct device_node *np)
> {
> return NULL;
> }
> +static inline struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np,
> + int port, int endpoint)
> +{
> + return -ENODEV;
> +}
> #endif
>
> static inline bool drm_bridge_is_last(struct drm_bridge *bridge)

--
Regards,

Laurent Pinchart