linux-kernel - [PATCH 3/9] drm/bridge: imx93-mipi-dsi: use drm_bridge_chain_get_last

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Message-Id: <20250709-drm-bridge-alloc-getput-drm_bridge_get_next_bridge-v1-3-48920b9cf369@bootlin.com>
Date: Wed, 09 Jul 2025 18:48:02 +0200
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>, 
 Liu Ying <victor.liu@....com>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, 
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, 
 Philipp Zabel <p.zabel@...gutronix.de>
Cc: Hui Pu <Hui.Pu@...ealthcare.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 Luca Ceresoli <luca.ceresoli@...tlin.com>
Subject: [PATCH 3/9] drm/bridge: imx93-mipi-dsi: use
 drm_bridge_chain_get_last_bridge()

Use drm_bridge_chain_get_last_bridge() instead of open coding a loop with
two invocations of drm_bridge_get_next_bridge() per iteration.

Besides being cleaner and more efficient, this change is necessary in
preparation for drm_bridge_get_next_bridge() to get a reference to the
returned bridge.

Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
---
 drivers/gpu/drm/bridge/imx/imx93-mipi-dsi.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/imx/imx93-mipi-dsi.c b/drivers/gpu/drm/bridge/imx/imx93-mipi-dsi.c
index bea8346515b8c8ce150040f58d288ac564eeb563..8f7a0d46601a41e1bfc04587398b0f1536a6a16c 100644
--- a/drivers/gpu/drm/bridge/imx/imx93-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/imx/imx93-mipi-dsi.c
@@ -492,14 +492,12 @@ static int imx93_dsi_get_phy_configure_opts(struct imx93_dsi *dsi,
 static enum drm_mode_status
 imx93_dsi_validate_mode(struct imx93_dsi *dsi, const struct drm_display_mode *mode)
 {
-	struct drm_bridge *bridge = dw_mipi_dsi_get_bridge(dsi->dmd);
+	struct drm_bridge *dmd_bridge = dw_mipi_dsi_get_bridge(dsi->dmd);
+	struct drm_bridge *last_bridge __free(drm_bridge_put) =
+		drm_bridge_chain_get_last_bridge(dmd_bridge->encoder);
 
-	/* Get the last bridge */
-	while (drm_bridge_get_next_bridge(bridge))
-		bridge = drm_bridge_get_next_bridge(bridge);
-
-	if ((bridge->ops & DRM_BRIDGE_OP_DETECT) &&
-	    (bridge->ops & DRM_BRIDGE_OP_EDID)) {
+	if ((last_bridge->ops & DRM_BRIDGE_OP_DETECT) &&
+	    (last_bridge->ops & DRM_BRIDGE_OP_EDID)) {
 		unsigned long pixel_clock_rate = mode->clock * 1000;
 		unsigned long rounded_rate;
 

-- 
2.50.0