From nobody Thu Dec 18 04:58:00 2025 Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) (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 780F13587C6 for ; Tue, 11 Nov 2025 12:01:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.171.202.116 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762862503; cv=none; b=lZFF0AHiGxa3qPtEIw3tRcxCc0dN8GUvPgaD1OEmbfuUSOc6AYlqijY0G6ggUav4Zv6DY2L44o8oa0hL5g5fAfuOf1DNMmxMvBrZ7zuanLn8CpKanrKCbpQPefSJgLfffsYcENm8vqJvO2IoKoeMwd1fkqTGfF5GYF5MCaMVYc4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762862503; c=relaxed/simple; bh=LB+IQzj/RyfVCejVXNOII9LYP9ZlKVcMW0+E8mu9ozU=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=kd7RE17VWyDixHxy8xXIKWwzGpI/WqZ/sv2DlpN01aE/HCchBauZ/tjQjFl1se6Okxd1L1i+fySmvJbnm9HghcgQKvK+79LifehELWlxhHfAyiNmS877AzoZ1xsqANEhc+9YZwSQpTtwu4glj+o1d2GTdjqcHn0hqsNX4q94IiM= 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=nd/M9dum; arc=none smtp.client-ip=185.171.202.116 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="nd/M9dum" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id 54CBDC0F544; Tue, 11 Nov 2025 12:01:18 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id D7034606FB; Tue, 11 Nov 2025 12:01:39 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 4444810371945; Tue, 11 Nov 2025 13:01:37 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1762862499; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=vFc4z5mhwogLuh5bJMqJoG/EPcrk5zOmeXK43n/q6e4=; b=nd/M9dumS9jfFht1mi1IHQgUT9ADWmkX7fbbov4XhGU3THhePmrttRfyvNPWebICWPplgY fzT2UVCdvp7xLLtzkbPoZp32qfNGGsmTjcolnWvqZq+cfor+DgmP0GnWLiTG81LEeTtRTr 1QZJR/uM1E+2KVGxbVafCGx37ERKphrNah8sFJCq/ahQGCi+MVlOFbHAcSMBN3JOjolqZd exs7AHHN6Ru671X7pZAJ7Sikr6IeTHO2yM+SwOYrUfMh5DwrG1ZynpaTcP/7dPFzdRX6Pl bMF1i6Q8jtzTYdTZHomu4jHPczrvZ3Aii/T9+NJyMzKN6hmC4AEG0KIGZ4i07g== From: Luca Ceresoli Date: Tue, 11 Nov 2025 13:01:25 +0100 Subject: [PATCH v4 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: <20251111-drm-bridge-alloc-encoder-chain-mutex-v4-5-12b13eb8c0f8@bootlin.com> References: <20251111-drm-bridge-alloc-encoder-chain-mutex-v4-0-12b13eb8c0f8@bootlin.com> In-Reply-To: <20251111-drm-bridge-alloc-encoder-chain-mutex-v4-0-12b13eb8c0f8@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, Luca Ceresoli X-Mailer: b4 0.14.2 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 c8389383e0d286c0d576ae1864ee783e002d44be..9b4a075b5361c34c61316c6e52f= e55c8928fbc13 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -627,7 +627,7 @@ 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 * @@ -641,17 +641,14 @@ 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) @@ -669,7 +666,7 @@ 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 * @@ -678,20 +675,16 @@ 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 @@ -915,7 +908,7 @@ 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 @@ -925,22 +918,18 @@ 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 2.51.1