linux-kernel - [PATCH v7 06/11] drm/bridge: get the bridge returned by drm_bridge_chain_get_first

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Message-Id: <20250314-drm-bridge-refcount-v7-6-152571f8c694@bootlin.com>
Date: Fri, 14 Mar 2025 11:31:19 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Marek Vasut <marex@...x.de>, Stefan Agner <stefan@...er.ch>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Inki Dae <inki.dae@...sung.com>, 
 Jagan Teki <jagan@...rulasolutions.com>, 
 Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Anusha Srivatsa <asrivats@...hat.com>, 
 Paul Kocialkowski <paulk@...-base.io>, Dmitry Baryshkov <lumag@...nel.org>, 
 Hervé Codina <herve.codina@...tlin.com>, 
 Hui Pu <Hui.Pu@...ealthcare.com>, dri-devel@...ts.freedesktop.org, 
 linux-kernel@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH v7 06/11] drm/bridge: get the bridge returned by
 drm_bridge_chain_get_first_bridge()

drm_bridge_chain_get_first_bridge() returns a bridge pointer that the
caller could hold for a long time. Increment the refcount of the returned
bridge and document it must be put by the caller.

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

---

This patch was added in v7.
---
 include/drm/drm_bridge.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index a5accd64c364ebb57903ae1e7459034ad9ebf4f3..d9777d5f2e9ef006f0062e4507bce99df4146cd9 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -1105,6 +1105,9 @@ drm_bridge_get_prev_bridge(struct drm_bridge *bridge)
  * drm_bridge_chain_get_first_bridge() - Get the first bridge in the chain
  * @encoder: encoder object
  *
+ * The refcount of the returned bridge is incremented. Use drm_bridge_put()
+ * when done with it.
+ *
  * RETURNS:
  * the first bridge in the chain, or NULL if @encoder has no bridge attached
  * to it.
@@ -1112,8 +1115,8 @@ drm_bridge_get_prev_bridge(struct drm_bridge *bridge)
 static inline struct drm_bridge *
 drm_bridge_chain_get_first_bridge(struct drm_encoder *encoder)
 {
-	return list_first_entry_or_null(&encoder->bridge_chain,
-					struct drm_bridge, chain_node);
+	return drm_bridge_get(list_first_entry_or_null(&encoder->bridge_chain,
+						       struct drm_bridge, chain_node));
 }
 
 /**

-- 
2.48.1