From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C8572606A31A for ; Thu, 29 Oct 2026 08:05:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=NGIS4mGN Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2D34C11207F; Thu, 29 Oct 2026 08:05:16 +0000 (UTC) Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 42D6711207C for ; Thu, 29 Oct 2026 08:04:58 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 2903643AC7 for ; Thu, 29 Oct 2026 08:04:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA1E51F01825; Thu, 29 Oct 2026 08:04:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793261098; bh=MGkWk+3v3aJ3oEqW4VfhWXyJ1zx4hnypMhWrIxpKJo4=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=NGIS4mGNXwaTja7te7ZFeSr1PC1x5fwFFHGu72oOe9aQgwog6CbyB5z68LvgXeyut YulJ3Ja0K46sdLOWY7i1h4BWoYUGCWDeiSaYFr/ZG077ekO1eJSS63giyYo9vypBuj cl54UCfvv+E9AvduX6Nr7+2qtO7s19Bx+ub0fmr1uohtFJ/4+Po5dLYGGmv2N+7pBJ 15RP2EYc9qBOU68hD3xXu7gLNxJJqRA4dQbdSu+z4+fnj7SUei4iE3+/NzYrGhKOp1 m3ynkIW+CkoJXbl4F/p4pCphm6L5OykUfKMBp8a3XXvhqFqFVOBX0fX93IIyxzbgid 1+7o/y6OdfBbA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v7 28/34] drm/bridge_connector: Implement hw readout for connector To: "Maxime Ripard" Cc: dri-devel@lists.freedesktop.org In-Reply-To: <20261029-drm-state-readout-v7-28-25e5163d75c3@kernel.org> References: <20261029-drm-state-readout-v7-0-25e5163d75c3@kernel.org> <20261029-drm-state-readout-v7-28-25e5163d75c3@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 29 Oct 2026 08:04:57 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "dri-devel" X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] drm/bridge_connector: unconditional SRO hooks with no-op readout w= hen unsupported -- commit b75d5f60d55bc26fbc8505149b2ac1fa7543a9a1 Author: Maxime Ripard drm/bridge_connector: Implement hw readout for connector This commit adds hardware state readout support to drm_bridge_connector by introducing DRM_BRIDGE_OP_CONNECTOR_HW_READOUT and the atomic_sro_connector_readout callback on drm_bridge_funcs. > diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu= /drm/display/drm_bridge_connector.c > index 81f3e26f6fdf5..45806ef077081 100644 > --- a/drivers/gpu/drm/display/drm_bridge_connector.c > +++ b/drivers/gpu/drm/display/drm_bridge_connector.c [ ... ] > @@ -244,6 +253,26 @@ drm_bridge_connector_create_state(struct drm_connect= or *connector) > return conn_state; > } > =20 > +static int > +drm_bridge_connector_readout_state(struct drm_connector *connector, > + struct drm_atomic_sro_state *state, > + struct drm_connector_state *conn_state) > +{ > + struct drm_bridge_connector *bridge_connector =3D > + to_drm_bridge_connector(connector); > + struct drm_bridge *readout =3D > + bridge_connector->bridge_connector_hw_readout; > + int ret; > + > + if (readout) { > + ret =3D readout->funcs->atomic_sro_connector_readout(readout, state, c= onn_state); > + if (ret) > + return ret; > + } > + > + return 0; > +} > + > static enum drm_connector_color_format > drm_bridge_connector_color_format(const struct drm_connector_state *conn= _state) > { > @@ -270,6 +299,8 @@ drm_bridge_connector_color_format(const struct drm_co= nnector_state *conn_state) > static const struct drm_connector_funcs drm_bridge_connector_funcs =3D { > .fill_modes =3D drm_helper_probe_single_connector_modes, > .atomic_create_state =3D drm_bridge_connector_create_state, > + .atomic_sro_readout_state =3D drm_bridge_connector_readout_state, > + .atomic_sro_compare_state =3D drm_atomic_helper_connector_compare_state, [Severity: High] Does unconditionally setting .atomic_sro_readout_state and .atomic_sro_compare_state on drm_bridge_connector_funcs while returning 0 in drm_bridge_connector_readout_state() when bridge_connector_hw_readout is NU= LL cause a regression for bridge chains without DRM_BRIDGE_OP_CONNECTOR_HW_REA= DOUT? In drivers/gpu/drm/drm_atomic_state_readout.c, drm_atomic_sro_can_readout() and drm_atomic_sro_can_compare() determine whether a connector supports sta= te readout by checking whether its callbacks are populated: drivers/gpu/drm/drm_atomic_state_readout.c:drm_atomic_sro_can_readout() { ... drm_connector_list_iter_begin(dev, &conn_iter); drm_for_each_connector_iter(connector, &conn_iter) { if (!connector->funcs->atomic_sro_readout_state) { drm_dbg_atomic(dev, "Connector %s missing readout callback", connector->name); drm_connector_list_iter_end(&conn_iter); return false; } } drm_connector_list_iter_end(&conn_iter); ... } Because drm_bridge_connector_funcs always defines both callbacks, every drm_bridge_connector is treated as supporting hardware state readout even w= hen no bridge in the chain sets DRM_BRIDGE_OP_CONNECTOR_HW_READOUT (leaving bridge_connector->bridge_connector_hw_readout NULL). When state readout runs on a pipeline where bridge_connector_hw_readout is NULL (for example, when bridges implement private state readout without any bridge setting DRM_BRIDGE_OP_CONNECTOR_HW_READOUT, on a multi-connector dev= ice where only one bridge chain supports connector readout, or when drm.atomic_readout is set to DRM_ATOMIC_READOUT_SKIP_MISSING_READOUT), drm_bridge_connector_readout_state() silently returns 0 and leaves conn_state->crtc and conn_state->best_encoder set to NULL. During initial readout in drm_mode_config_create_initial_state() -> drm_atomic_helper_sro_readout_state() -> drm_atomic_helper_sro_build_state(= ), this causes drm_bridge_atomic_readout_priv_state() in drivers/gpu/drm/drm_bridge.c to skip reading out all bridges on that encode= r's chain because find_connector_state_for_encoder() matches encoder against conn_state->best_encoder: drivers/gpu/drm/drm_bridge.c:drm_bridge_atomic_readout_priv_state() { ... conn_state =3D find_connector_state_for_encoder(state, encoder); if (!conn_state) return 0; if (!conn_state->crtc) return 0; ... } It also installs an inconsistent atomic state via drm_atomic_sro_install_state() with an active CRTC (crtc_state->active =3D= =3D true and crtc_state->connector_mask =3D=3D 0) and a disconnected connector state instead of failing readout and falling back to hw_reset(). Furthermore, dur= ing post-commit verification in commit_tail() -> drm_atomic_sro_readout_and_compare(), every blocking commit enabling that connector compares the committed active state against the unpopulated reado= ut state via drm_atomic_helper_connector_compare_state(), drm_atomic_helper_crtc_compare_state(), and drm_atomic_helper_bridge_compare_state(), triggering state mismatch errors. Should drm_bridge_connector_init() only expose a drm_connector_funcs table with .atomic_sro_readout_state and .atomic_sro_compare_state when bridge_connector->bridge_connector_hw_readout is non-NULL (similar to how drm_bridge_attach() selects between drm_bridge_priv_state_funcs and drm_bridge_priv_state_funcs_with_sro)? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261029-drm-state-= readout-v7-0-25e5163d75c3@kernel.org?part=3D28