From: Luca Ceresoli <luca.ceresoli@bootlin.com>
Date: Mon, 11 May 2026 16:40:15 +0000 (+0200)
Subject: drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0d5da248ea2d7802a5055ab6762340ac870bd0ee;p=thirdparty%2Fkernel%2Flinux.git

drm: of: forbid bridge-only calls to drm_of_find_panel_or_bridge()

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>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-11-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index ef6b093169637..d03ada82eac96 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) {