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

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

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