Re: [PATCH v4 11/11] drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

Laurent Pinchart
2026-05-04T15:27:48Z

On Mon, May 04, 2026 at 12:45:14PM +0200, Luca Ceresoli wrote:
> Up to now drm_of_find_panel_or_bridge() can be called with a bridge pointer
> only, a panel pointer only, or both a bridge and a panel pointers. The
> logic to handle all the three cases is somewhat complex to read however.
>
> Now all bridge-only callers have been converted to
> of_drm_get_bridge_by_endpoint(), which is simpler and handles bridge
> refcounting. So forbid new bridge-only users by mandating a non-NULL panel
> pointer in the docs and in the sanity checks along with a warning.
>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

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

> ---
> drivers/gpu/drm/drm_of.c | 26 ++++++++++++--------------
> 1 file changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index ef6b09316963..d03ada82eac9 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -225,15 +225,15 @@ EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);
> * @np: device tree node containing encoder output ports
> * @port: port in the device tree node
> * @endpoint: endpoint in the device tree node
> - * @panel: pointer to hold returned drm_panel
> + * @panel: pointer to hold returned drm_panel, must not be NULL
> * @bridge: pointer to hold returned drm_bridge
> *
> * Given a DT node's port and endpoint number, find the connected node and
> - * return either the associated struct drm_panel or drm_bridge device. Either
> - * @panel or @bridge must not be NULL.
> + * return either the associated struct drm_panel or drm_bridge device.
> *
> * This function is deprecated and should not be used in new drivers. Use
> - * devm_drm_of_get_bridge() instead.
> + * of_drm_get_bridge_by_endpoint() instead when not looking for a panel, or
> + * devm_drm_of_get_bridge() otherwise.
> *
> * Returns zero if successful, or one of the standard error codes if it fails.
> */
> @@ -245,10 +245,10 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> int ret = -EPROBE_DEFER;
> struct device_node *remote;
>
> - if (!panel && !bridge)
> + if (WARN_ON(!panel))
> return -EINVAL;
> - if (panel)
> - *panel = NULL;
> +
> + *panel = NULL;
>
> /*
> * of_graph_get_remote_node() produces a noisy error message if port
> @@ -263,13 +263,11 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> if (!remote)
> return -ENODEV;
>
> - if (panel) {
> - *panel = of_drm_find_panel(remote);
> - if (!IS_ERR(*panel))
> - ret = 0;
> - else
> - *panel = NULL;
> - }
> + *panel = of_drm_find_panel(remote);
> + if (!IS_ERR(*panel))
> + ret = 0;
> + else
> + *panel = NULL;
>
> if (bridge) {
> if (ret) {
>

--
Regards,

Laurent Pinchart