linux-kernel - [PATCH v3 21/22] drm/bridge: panel: convert to devm_drm_bridge

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Message-Id: <20250509-drm-bridge-convert-to-alloc-api-v3-21-b8bc1f16d7aa@bootlin.com>
Date: Fri, 09 May 2025 15:53:47 +0200
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: 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>, 
 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>, 
 Jagan Teki <jagan@...rulasolutions.com>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, 
 Douglas Anderson <dianders@...omium.org>, 
 Chun-Kuang Hu <chunkuang.hu@...nel.org>, 
 Krzysztof Kozlowski <krzk@...nel.org>
Cc: Anusha Srivatsa <asrivats@...hat.com>, 
 Paul Kocialkowski <paulk@...-base.io>, Dmitry Baryshkov <lumag@...nel.org>, 
 Hui Pu <Hui.Pu@...ealthcare.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 dri-devel@...ts.freedesktop.org, asahi@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev, 
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 linux-mediatek@...ts.infradead.org, linux-amlogic@...ts.infradead.org, 
 linux-renesas-soc@...r.kernel.org, platform-driver-x86@...r.kernel.org, 
 linux-samsung-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 freedreno@...ts.freedesktop.org, linux-stm32@...md-mailman.stormreply.com, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH v3 21/22] drm/bridge: panel: convert to
 devm_drm_bridge_alloc() API

This is the new API for allocating DRM bridges.

The devm lifetime management of this driver is peculiar. The underlying
device for the panel_bridge is the panel, and the devm lifetime is tied the
panel device (panel->dev). However the panel_bridge allocation is not
performed by the panel driver, but rather by a separate entity (typically
the previous bridge in the encoder chain).

Thus when that separate entity is destroyed, the panel_bridge is not
removed automatically by devm, so it is rather done explicitly by calling
drm_panel_bridge_remove(). This is the function that does devm_kfree() the
panel_bridge in current code, so update it as well to put the bridge
reference instead.

This is a temporary solution until the panel lifetime is reworked, which
should make this workaround unnecessary, so add a comment to clarify that.

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

---

Changes in v3:
- add TODO to remove devm_drm_put_bridge(), update commit message
- fix typo in commit message

Changes in v2: none
---
 drivers/gpu/drm/bridge/panel.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 79b009ab9396048eac57ad47631a902e949d77c6..6cbbfb1381a4a75fbc3acf6e6c5361202627e740 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -287,15 +287,14 @@ struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
 	if (!panel)
 		return ERR_PTR(-EINVAL);
 
-	panel_bridge = devm_kzalloc(panel->dev, sizeof(*panel_bridge),
-				    GFP_KERNEL);
-	if (!panel_bridge)
-		return ERR_PTR(-ENOMEM);
+	panel_bridge = devm_drm_bridge_alloc(panel->dev, struct panel_bridge, bridge,
+					     &panel_bridge_bridge_funcs);
+	if (IS_ERR(panel_bridge))
+		return (void *)panel_bridge;
 
 	panel_bridge->connector_type = connector_type;
 	panel_bridge->panel = panel;
 
-	panel_bridge->bridge.funcs = &panel_bridge_bridge_funcs;
 	panel_bridge->bridge.of_node = panel->dev->of_node;
 	panel_bridge->bridge.ops = DRM_BRIDGE_OP_MODES;
 	panel_bridge->bridge.type = connector_type;
@@ -327,7 +326,8 @@ void drm_panel_bridge_remove(struct drm_bridge *bridge)
 	panel_bridge = drm_bridge_to_panel_bridge(bridge);
 
 	drm_bridge_remove(bridge);
-	devm_kfree(panel_bridge->panel->dev, bridge);
+	/* TODO remove this after reworking panel_bridge lifetime */
+	devm_drm_put_bridge(panel_bridge->panel->dev, bridge);
 }
 EXPORT_SYMBOL(drm_panel_bridge_remove);
 

-- 
2.49.0