[PATCH v2 11/11] drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

Luca Ceresoli
2026-04-28T09:17:11Z

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.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.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) {

--
2.53.0