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 ef6b093169637ad210124a2ff75ce9865e21736f..d03ada82eac96e8c449ba80a1b1148c6589be0f6 100644 (file)
--- 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) {