linux-kernel - [PATCH v6 16/26] drm/bridge: increment refcount in of_drm_find

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Message-Id: <20250206-hotplug-drm-bridge-v6-16-9d6f2c9c3058@bootlin.com>
Date: Thu, 06 Feb 2025 19:14:31 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Simona Vetter <simona@...ll.ch>, Inki Dae <inki.dae@...sung.com>, 
 Jagan Teki <jagan@...rulasolutions.com>, 
 Marek Szyprowski <m.szyprowski@...sung.com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Daniel Thompson <danielt@...nel.org>, 
 Andrzej Hajda <andrzej.hajda@...el.com>, Jonathan Corbet <corbet@....net>, 
 Sam Ravnborg <sam@...nborg.org>, Boris Brezillon <bbrezillon@...nel.org>, 
 Nicolas Ferre <nicolas.ferre@...rochip.com>, 
 Alexandre Belloni <alexandre.belloni@...tlin.com>, 
 Claudiu Beznea <claudiu.beznea@...on.dev>, 
 Jessica Zhang <quic_jesszhan@...cinc.com>
Cc: Paul Kocialkowski <contact@...lk.fr>, 
 Maxime Ripard <mripard@...nel.org>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
 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>, 
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
 Hervé Codina <herve.codina@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 Paul Kocialkowski <paul.kocialkowski@...tlin.com>, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH v6 16/26] drm/bridge: increment refcount in
 of_drm_find_bridge()

of_drm_find_bridge() returns a pointer to a bridge, so it has to get a
reference and the caller will be in charge of putting it.

Callers of of_drm_find_bridge() are:

 1. drm_of_panel_bridge_remove()
 2. of_drm_find_bridge_by_endpoint()
 3. drm_of_find_panel_or_bridge()
 4. various DRM drivers

Add the corresponding drm_bridge_put() call for 1 and propagate
documentation to 2 and 3.

Other callers (4) are to be adapted in following commits.

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

---

This patch was added in v6.
---
 drivers/gpu/drm/bridge/panel.c | 3 +++
 drivers/gpu/drm/drm_bridge.c   | 7 +++++++
 include/drm/drm_of.h           | 1 +
 3 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 1230ae50b2020e7a9306cac83009dd600dd61d26..3c0e22e61c1092de1571d800ac440aad7b5c86bc 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -363,6 +363,9 @@ EXPORT_SYMBOL(of_drm_find_panel);
  * return either the associated struct drm_panel or drm_bridge device. Either
  * @panel or @bridge must not be NULL.
  *
+ * If a bridge is returned in @bridge, the bridge refcount is
+ * incremented. Use drm_bridge_put() when done with the bridge.
+ *
  * This function is deprecated and should not be used in new drivers. Use
  * devm_drm_of_get_bridge() instead.
  *
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 497ec06dfcb05ab5dee8ea5e8f1eafb9c2807612..fca860d582f86b35c9172b27be20060de086e38f 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -1396,6 +1396,9 @@ EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
  *
  * @np: device node
  *
+ * On return the bridge refcount is incremented (if the bridge is
+ * refcounted). Use drm_bridge_put() when done with the bridge.
+ *
  * RETURNS:
  * drm_bridge control struct on success, NULL on failure
  */
@@ -1407,6 +1410,7 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np)
 
 	list_for_each_entry(bridge, &bridge_list, list) {
 		if (bridge->of_node == np) {
+			drm_bridge_get(bridge);
 			mutex_unlock(&bridge_lock);
 			return bridge;
 		}
@@ -1427,6 +1431,9 @@ EXPORT_SYMBOL(of_drm_find_bridge);
  * Given a DT node's port and endpoint number, find the connected node and
  * return the associated struct drm_bridge.
  *
+ * On success the returned @bridge refcount is incremented. Use
+ * drm_bridge_put() when done with the bridge.
+ *
  * Returns zero if successful, or one of the standard error codes if it fails.
  */
 static int of_drm_find_bridge_by_endpoint(const struct device_node *np,
diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
index 7f0256dae3f13de1d4109e9265d66684ef2a08ee..948672c27d2eb3034b2519e0bba0fcb52d5c697b 100644
--- a/include/drm/drm_of.h
+++ b/include/drm/drm_of.h
@@ -172,6 +172,7 @@ static inline int drm_of_panel_bridge_remove(const struct device_node *np,
 
 	bridge = of_drm_find_bridge(remote);
 	drm_panel_bridge_remove(bridge);
+	drm_bridge_put(bridge);
 
 	return 0;
 #else

-- 
2.34.1