Re: [PATCH v6 10/26] drm/bridge: add devm_drm_of_get_bridge_by_node()

[Maxime Ripard <mripard@kernel.org>]

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On Thu, Feb 06, 2025 at 07:14:25PM +0100, Luca Ceresoli wrote:
> devm_drm_of_get_bridge(), which is based on graph links, is the recommended
> function to get a pointer to the following bridge.
> 
> This is valid even for panels, for which the recommended device tree
> description is via graph links and not (or not only) panel subnodes of a
> panel controller (e.g. "dsi@1234" controller node with a "panel@0"
> subnode).
> 
> However there are drivers supporting the panel subnode description in
> addition to the graph links. For those drivers add a _by_node variant that
> takes the node of the target node.
> 
> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> 
> ---
> 
> This patch was added in v6.
> ---
>  drivers/gpu/drm/drm_bridge.c | 30 ++++++++++++++++++++++++++++++
>  include/drm/drm_bridge.h     |  8 ++++++++
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 2aa17fbe538b86066c4e68f0d0e8046e9ca9b965..b0834b8644284e5f7751cec81724af849b4180e7 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -1407,6 +1407,36 @@ struct drm_bridge *devm_drm_of_get_bridge(struct device *dev,
>  }
>  EXPORT_SYMBOL(devm_drm_of_get_bridge);
>  
> +/**
> + * devm_drm_of_get_bridge_by_node - Return bridge for a given OF node
> + * @dev: device to tie the bridge lifetime to
> + * @bridge_node: device node of the remote bridge
> + *
> + * Given a bridge DT node, returns the associated bridge if any. This
> + * should be used in addition to devm_drm_of_get_bridge() when the regular
> + * graph link search is not enough, e.g. for drivers that need to support
> + * panels described only as subnodes.
> + *
> + * RETURNS:
> + * A pointer to the bridge if successful, or an error pointer otherwise.
> + */
> +struct drm_bridge *devm_drm_of_get_bridge_by_node(struct device *dev,
> +						  struct device_node *bridge_node)
> +{
> +	struct drm_bridge *bridge;
> +	int ret;
> +
> +	if (!bridge_node)
> +		return ERR_PTR(-EINVAL);
> +
> +	bridge = of_drm_find_bridge(bridge_node);
> +	if (!bridge)
> +		return ERR_PTR(-ENODEV);
> +
> +	return bridge;
> +}
> +EXPORT_SYMBOL(devm_drm_of_get_bridge_by_node);
> +

A bridge is a KMS-facing structure, there's no reason to tie it to the
lifetime of the device.

Maxime

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