[PATCH v7 04/11] drm/bridge: get/put the bridge reference in drm_bridge_attach/detach()

From: Luca Ceresoli
Date: Fri Mar 14 2025 - 06:32:36 EST


drm_bridge_attach() adds the bridge to the encoder chain, so take a
reference for that. Vice versa in drm_bridge_detach().

Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>

---

Changes in v7:
- in v6 this was part of "drm/bridge: add support for refcounted DRM
bridges", now split to a separate patch
---
drivers/gpu/drm/drm_bridge.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 72fa51d4dd2337f97c2bd65cfabf9cee05b661b4..da85694e9310f1f910bc8a5aa5d95a91d9254888 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -370,11 +370,17 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
if (!encoder || !bridge)
return -EINVAL;

- if (previous && (!previous->dev || previous->encoder != encoder))
- return -EINVAL;
+ drm_bridge_get(bridge);

- if (bridge->dev)
- return -EBUSY;
+ if (previous && (!previous->dev || previous->encoder != encoder)) {
+ ret = -EINVAL;
+ goto err_put_bridge;
+ }
+
+ if (bridge->dev) {
+ ret = -EBUSY;
+ goto err_put_bridge;
+ }

bridge->dev = encoder->dev;
bridge->encoder = encoder;
@@ -423,6 +429,8 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
"failed to attach bridge %pOF to encoder %s\n",
bridge->of_node, encoder->name);

+err_put_bridge:
+ drm_bridge_put(bridge);
return ret;
}
EXPORT_SYMBOL(drm_bridge_attach);
@@ -443,6 +451,7 @@ void drm_bridge_detach(struct drm_bridge *bridge)

list_del(&bridge->chain_node);
bridge->dev = NULL;
+ drm_bridge_put(bridge);
}

/**

--
2.48.1