From patchwork Mon Apr 14 08:56:56 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Simon Ser X-Patchwork-Id: 14049991 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 4467CC369B5 for ; Mon, 14 Apr 2025 08:57:05 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 86A1310E4EF; Mon, 14 Apr 2025 08:57:04 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=emersion.fr header.i=@emersion.fr header.b="HjMkixnr"; dkim-atps=neutral Received: from mail-24421.protonmail.ch (mail-24421.protonmail.ch [109.224.244.21]) by gabe.freedesktop.org (Postfix) with ESMTPS id E7D9710E4F0 for ; Mon, 14 Apr 2025 08:57:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=emersion.fr; s=protonmail2; t=1744621021; x=1744880221; bh=TvkVY4A11Ky4AInNyJMcsXNiwfKw52Njv39xoQElgOA=; h=Date:To:From:Cc:Subject:Message-ID:Feedback-ID:From:To:Cc:Date: Subject:Reply-To:Feedback-ID:Message-ID:BIMI-Selector: List-Unsubscribe:List-Unsubscribe-Post; b=HjMkixnrGbqKTgJwYJebo4W9/n/yVrxsI4gcrKLSNqxaHf1xcS2pN3WfxxeG9hAFk TjgXH1m0ev98fdyUVQgCtmFVHAMdUtm27pZIUxtTEPDM+iQY8KyXqc8vkrLOEVL1XV jz0ZgjqOzt1/yv4cZv9fNIbtV3BXsX2E1wV3Ag5BMHsbYsupBHjbbS9UQwRBEx/geu VjNCZwnOGyaxD94BunttKwzjT7Htjc85M9hkKfLuaNImI7BvuWDgPqYvPk5PczsgZ9 fZfBcq7jUl22vrKfChRYls1HXQJ6nm2Mnhr0+Hlx1OMMcH1jOGfeZApRLFMZRsYWNz T7CB/ghamILjQ== Date: Mon, 14 Apr 2025 08:56:56 +0000 To: dri-devel@lists.freedesktop.org From: Simon Ser Cc: Pekka Paalanen , Simona Vetter Subject: [PATCH v2] drm/doc: document front-buffer rendering Message-ID: <20250414085652.43904-1-contact@emersion.fr> Feedback-ID: 1358184:user:proton X-Pm-Message-ID: 1e57691d9024a475234a0e72201fa9c23ca447f0 MIME-Version: 1.0 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Explain how to perform front-buffer rendering. v2: apply Pekka's rewrite Signed-off-by: Simon Ser Cc: Pekka Paalanen Cc: Simona Vetter --- drivers/gpu/drm/drm_blend.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c index 6e74de833466..4e83f372ea51 100644 --- a/drivers/gpu/drm/drm_blend.c +++ b/drivers/gpu/drm/drm_blend.c @@ -75,6 +75,12 @@ * the currently visible vertical area of the &drm_crtc. * FB_ID: * Mode object ID of the &drm_framebuffer this plane should scan out. + * + * When a KMS client is perfoming front-buffer rendering, it should set + * FB_ID to the same front-buffer FB on each atomic commit. This implies + * to the driver that it needs to re-read the same FB again. Otherwise + * drivers which do not employ continuously repeated scanout cycles might + * not update the screen. * CRTC_ID: * Mode object ID of the &drm_crtc this plane should be connected to. *