From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9CDA2C46467 for ; Wed, 11 Jan 2023 14:17:41 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id AC00610E749; Wed, 11 Jan 2023 14:17:39 +0000 (UTC) Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0441010E2B3 for ; Wed, 11 Jan 2023 14:17:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1673446656; x=1704982656; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=fmJ8Bb9kgdkiYyjCAW2Eyzd2POxa83xS29bXEsoljHM=; b=LyW6jFSSrRIvxT1rAJEySLC7MpJMk+b/ZrarVwlDfif0fzSSwzaxWfdf zSIYlyjcGgNj4K/7h42GPo+wqfZ2NgmgZzlpDC6mawRSzlhBF2hdgMmBO 4tcAWx/6Ul+WkQAk7FhrR+/v7IxYz02fLX4RqaFXdjqxJ0gbcRBDoFJs1 FnCv1mCI44d2c1qObIIOMmYKBfXCLhFcTY7SccM8xS488rtXOPvv45Zqr LcAi59LRs5IQyTLuRr/+KzOmbIOfKuUS/uICp6j4BvVj5jLIdEitNajxm h6UGcoqAZxgp1K3XFmYltlnyfSV64O0+iecWzI1d/t/u/M1Li5pySwL50 g==; X-IronPort-AV: E=McAfee;i="6500,9779,10586"; a="306937344" X-IronPort-AV: E=Sophos;i="5.96,317,1665471600"; d="scan'208";a="306937344" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2023 06:17:18 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10586"; a="765159886" X-IronPort-AV: E=Sophos;i="5.96,317,1665471600"; d="scan'208";a="765159886" Received: from mmgriffi-mobl.ger.corp.intel.com (HELO localhost) ([10.252.11.225]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2023 06:17:14 -0800 From: Jani Nikula To: Thomas Zimmermann , Maxime Ripard , Emma Anholt , Maxime Ripard , David Airlie , Daniel Vetter Subject: Re: [PATCH 2/9] drm/vc4: hdmi: Constify container_of wrappers In-Reply-To: <38a5f052-18d5-5297-f1c7-44ca5b8285f5@suse.de> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20221207-rpi-hdmi-improvements-v1-0-6b15f774c13a@cerno.tech> <20221207-rpi-hdmi-improvements-v1-2-6b15f774c13a@cerno.tech> <38a5f052-18d5-5297-f1c7-44ca5b8285f5@suse.de> Date: Wed, 11 Jan 2023 16:17:12 +0200 Message-ID: <87wn5tgnpz.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Dave Stevenson Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Wed, 11 Jan 2023, Thomas Zimmermann wrote: > Hi > > Am 07.12.22 um 17:07 schrieb Maxime Ripard: >> None of our wrappers around container_of to access our objects from the >> DRM object pointer actually modify the latter. >> >> Let's make them const. >> >> Signed-off-by: Maxime Ripard > > Personally, I wouldn't take this patch as it does an implicit const cast > on the pointer. > > For const correctness, it seems better to add new helpers that keep the > const. Those could be use in places where the caller is not allowed to > modify the state (i.e., atomic_update, et al). > > Something like this: > > const struct vc4_hdmi * > const_connector_to_vc4_hdmi(const struct drm_connector *connector) > { > return container_of(connector, const struct vc4_hdmi, > connector); > } See container_of_const(). BR, Jani. > > Best regards > Thomas > >> --- >> drivers/gpu/drm/vc4/vc4_hdmi.h | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h >> index dc3ccd8002a0..023ea64ef006 100644 >> --- a/drivers/gpu/drm/vc4/vc4_hdmi.h >> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h >> @@ -224,13 +224,13 @@ struct vc4_hdmi { >> }; >> >> static inline struct vc4_hdmi * >> -connector_to_vc4_hdmi(struct drm_connector *connector) >> +connector_to_vc4_hdmi(const struct drm_connector *connector) >> { >> return container_of(connector, struct vc4_hdmi, connector); >> } >> >> static inline struct vc4_hdmi * >> -encoder_to_vc4_hdmi(struct drm_encoder *encoder) >> +encoder_to_vc4_hdmi(const struct drm_encoder *encoder) >> { >> struct vc4_encoder *_encoder = to_vc4_encoder(encoder); >> return container_of(_encoder, struct vc4_hdmi, encoder); >> @@ -244,7 +244,7 @@ struct vc4_hdmi_connector_state { >> }; >> >> static inline struct vc4_hdmi_connector_state * >> -conn_state_to_vc4_hdmi_conn_state(struct drm_connector_state *conn_state) >> +conn_state_to_vc4_hdmi_conn_state(const struct drm_connector_state *conn_state) >> { >> return container_of(conn_state, struct vc4_hdmi_connector_state, base); >> } >> -- Jani Nikula, Intel Open Source Graphics Center