From nobody Thu Apr 2 23:31:25 2026 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 334E83D9DD7 for ; Tue, 24 Mar 2026 08:58:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774342723; cv=none; b=LtYm2Boy7dzrWrN7fVQ6MFuO2+AORtmPBz+8SyVBsYV6hVUj4rOdd1wQYek1MUTjnhBnaoe92bAPRmWTz6oJLJUaNyCIw4/kcp0PUzkf0QzI3psONLDH9VF3B/x5u9I6XzvBcZzyYoiTRHEg0hOQTk8mE8BxefoxuBmHTNfSo9U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774342723; c=relaxed/simple; bh=pTn1kI7GaZJwfEy3QeOwCzyeAoTorItqLv2fj7/2FIk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Mfd7pCRJwO03xRsYuQEtLWTt3SprgW+bPh/vt+ikddXi4L4kt9+Bi7E1o6yy6lYzB3ueFBjmun90fABBSY3lCdEagbFQCPwFfdab87IRYMz5auWeu7UWNrKywhJkz8A0grPyxpzm8f8B7WrUHBhD2ljaPm4eNebVWrES1OUVX/Q= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=OKw1YMxP; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="OKw1YMxP" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id 025441A2FC1; Tue, 24 Mar 2026 08:58:41 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id C689E6011D; Tue, 24 Mar 2026 08:58:40 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 151AA10451140; Tue, 24 Mar 2026 09:58:36 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1774342719; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=8mMcYEXUydZGS/Fj4aUMVLorw/18mDZTJVFYNGb7XMU=; b=OKw1YMxPQSbqPviE7lZb7Y5jieL3u4cLiz2S2nUo4eSx+5JokOgnDrZaIHHF0y02LT0mHt rss3/bSjgNYJsJ+aGjCOuWFEpeF0JBIbRxL4JwwT4OoO3UT3USGNerr3saWXm21Fcl7qDU nTDcc1SGM3YkqfobgsLsSywcHqYCtyjMrlTSYlon/km1jXQa4UEX6TdumtAHRYkUS7TaB5 UTXebyG1KF9x9inoeUzDC394kwqG3Mc2laPbc2+mgsYz865T0806zuHysqXZJIARDgIH7s VLByfDXLWRSIvsfDjS+f8jFDS2xaczRYlAUz5KSsMAYdKGbn2jRlJvokQInGOQ== From: Luca Ceresoli Date: Tue, 24 Mar 2026 09:58:12 +0100 Subject: [PATCH v5 5/7] drm/bridge: prevent encoder chain changes while iterating with list_for_each_entry_from() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-5-8bf786c5c7e6@bootlin.com> References: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-0-8bf786c5c7e6@bootlin.com> In-Reply-To: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-0-8bf786c5c7e6@bootlin.com> To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec Cc: Hui Pu , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Ian Ray , Luca Ceresoli X-Mailer: b4 0.14.3 X-Last-TLS-Session-Version: TLSv1.3 These loops in drm_bridge.c iterate over the encoder chain using list_for_each_entry_from(), which does not prevent changes to the bridge chain while iterating over it. Convert most of those loops to instead use drm_for_each_bridge_in_chain_from(), which locks the chain. This also simplifies code. All the "simple" loops are converted here. The only ones not touched are those in drm_atomic_bridge_chain_pre_enable() and drm_atomic_bridge_chain_post_disable(), because they have nested loops which are not well handled by drm_for_each_bridge_in_chain_from(). Those two functions are handled by a separate commit. Signed-off-by: Luca Ceresoli --- drivers/gpu/drm/drm_bridge.c | 35 ++++++++++++----------------------- 1 file changed, 12 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index 42ca4b243579..37feb8143de4 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -725,7 +725,7 @@ void drm_bridge_detach(struct drm_bridge *bridge) /** * drm_bridge_chain_mode_valid - validate the mode against all bridges in = the * encoder chain. - * @bridge: bridge control structure + * @first_bridge: bridge control structure * @info: display info against which the mode shall be validated * @mode: desired mode to be validated * @@ -739,17 +739,14 @@ void drm_bridge_detach(struct drm_bridge *bridge) * MODE_OK on success, drm_mode_status Enum error code on failure */ enum drm_mode_status -drm_bridge_chain_mode_valid(struct drm_bridge *bridge, +drm_bridge_chain_mode_valid(struct drm_bridge *first_bridge, const struct drm_display_info *info, const struct drm_display_mode *mode) { - struct drm_encoder *encoder; - - if (!bridge) + if (!first_bridge) return MODE_OK; =20 - encoder =3D bridge->encoder; - list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) { + drm_for_each_bridge_in_chain_from(first_bridge, bridge) { enum drm_mode_status ret; =20 if (!bridge->funcs->mode_valid) @@ -767,7 +764,7 @@ EXPORT_SYMBOL(drm_bridge_chain_mode_valid); /** * drm_bridge_chain_mode_set - set proposed mode for all bridges in the * encoder chain - * @bridge: bridge control structure + * @first_bridge: bridge control structure * @mode: desired mode to be set for the encoder chain * @adjusted_mode: updated mode that works for this encoder chain * @@ -776,20 +773,16 @@ EXPORT_SYMBOL(drm_bridge_chain_mode_valid); * * Note: the bridge passed should be the one closest to the encoder */ -void drm_bridge_chain_mode_set(struct drm_bridge *bridge, +void drm_bridge_chain_mode_set(struct drm_bridge *first_bridge, const struct drm_display_mode *mode, const struct drm_display_mode *adjusted_mode) { - struct drm_encoder *encoder; - - if (!bridge) + if (!first_bridge) return; =20 - encoder =3D bridge->encoder; - list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) { + drm_for_each_bridge_in_chain_from(first_bridge, bridge) if (bridge->funcs->mode_set) bridge->funcs->mode_set(bridge, mode, adjusted_mode); - } } EXPORT_SYMBOL(drm_bridge_chain_mode_set); =20 @@ -1013,7 +1006,7 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable); =20 /** * drm_atomic_bridge_chain_enable - enables all bridges in the encoder cha= in - * @bridge: bridge control structure + * @first_bridge: bridge control structure * @state: atomic state being committed * * Calls &drm_bridge_funcs.atomic_enable (falls back on @@ -1023,22 +1016,18 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable); * * Note: the bridge passed should be the one closest to the encoder */ -void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge, +void drm_atomic_bridge_chain_enable(struct drm_bridge *first_bridge, struct drm_atomic_state *state) { - struct drm_encoder *encoder; - - if (!bridge) + if (!first_bridge) return; =20 - encoder =3D bridge->encoder; - list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) { + drm_for_each_bridge_in_chain_from(first_bridge, bridge) if (bridge->funcs->atomic_enable) { bridge->funcs->atomic_enable(bridge, state); } else if (bridge->funcs->enable) { bridge->funcs->enable(bridge); } - } } EXPORT_SYMBOL(drm_atomic_bridge_chain_enable); =20 --=20 2.53.0