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 7DB7DEE208F for ; Fri, 6 Feb 2026 11:23:13 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id DEAB110E149; Fri, 6 Feb 2026 11:23:12 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=collabora.com header.i=@collabora.com header.b="F/JGyWbk"; dkim-atps=neutral Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1694710E149 for ; Fri, 6 Feb 2026 11:23:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1770376989; bh=6wXD6mAlRplT43SZrDzHqzDpt95fasANM63SHkqxKYs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=F/JGyWbkOxIpZx4vmZazuYzcSFBfjZnyZchDKpmvwCOop6apAYveFcAkQXaLTugqO 5/t5pwXrmDjVrCe8vhomcFQgKCzKmCZ4Y+IBU/r/jOE4hzKcLa8ywKkP6rezQ86jth qjtnxsS7SCzXXVEB6pAKV19mb1AnCLwvP4hwh0VFXOgCG6xCeaZ3lfHDUJ6sdRoFUo rVgp8ewsoKKZQHJ3lD1VVM/GyDtYhm2tDUbK/zN+IBBXktur6sIsQcrIbPlv0aAR4o ja8HUUme+uTjNKkxAKCyZkL7nAdBIKIOtyMeBoj/YFIvGofflR5XRgtTdod6rZ7fQK DrTg9QToLnz3Q== Received: from fedora (unknown [IPv6:2a01:e0a:2c:6930:d919:a6e:5ea1:8a9f]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 19A8C17E01E7; Fri, 6 Feb 2026 12:23:09 +0100 (CET) Date: Fri, 6 Feb 2026 12:23:04 +0100 From: Boris Brezillon To: Philipp Stanner Cc: phasta@kernel.org, Gary Guo , David Airlie , Simona Vetter , Danilo Krummrich , Alice Ryhl , Benno Lossin , Christian =?UTF-8?B?S8O2bmln?= , Daniel Almeida , Joel Fernandes , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, rust-for-linux@vger.kernel.org Subject: Re: [RFC PATCH 2/4] rust: sync: Add dma_fence abstractions Message-ID: <20260206122304.2820c375@fedora> In-Reply-To: <62b82ffdd40d568d822bda8cdea83cd030851f68.camel@mailbox.org> References: <20260203081403.68733-2-phasta@kernel.org> <20260203081403.68733-4-phasta@kernel.org> <20260205111635.5307e1fa@fedora> <62b82ffdd40d568d822bda8cdea83cd030851f68.camel@mailbox.org> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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" On Fri, 06 Feb 2026 10:32:38 +0100 Philipp Stanner wrote: > On Thu, 2026-02-05 at 13:16 +0000, Gary Guo wrote: > > On Thu Feb 5, 2026 at 10:16 AM GMT, Boris Brezillon wrote: =20 > > > On Tue,=C2=A0 3 Feb 2026 09:14:01 +0100 > > > Philipp Stanner wrote: > > > =20 > > > > =20 >=20 > [=E2=80=A6] >=20 > > > > +#[pin_data] > > > > +pub struct DmaFence { > > > > +=C2=A0=C2=A0=C2=A0 /// The actual dma_fence passed to C. > > > > +=C2=A0=C2=A0=C2=A0 #[pin] > > > > +=C2=A0=C2=A0=C2=A0 inner: Opaque, > > > > +=C2=A0=C2=A0=C2=A0 /// User data. > > > > +=C2=A0=C2=A0=C2=A0 #[pin] > > > > +=C2=A0=C2=A0=C2=A0 data: T, =20 > > >=20 > > > A DmaFence is a cross-device synchronization mechanism that can (and > > > will) > > > =20 >=20 > I'm not questioning the truth behind this statement. They are designed > to do that. But is that actually being done, currently? I recently > found that the get_driver_name() callback intended to inform the > consumer of a fence about who actually issued the fence is only ever > used by i915. It's also used by the dma-buf layer to expose info about dma-bufs through debugfs (see dma_{fence,resv}_describe() and dma_buf_debug_show()), meaning all GPU drivers adding their fences to the dma_resv of an imported/exported buffer object should expect to have their ::get_{driver,timeline}_name() implementation called.