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 3858DCD4F3C for ; Mon, 18 May 2026 15:07:08 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9558910E8E5; Mon, 18 May 2026 15:07:07 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=amd.com header.i=@amd.com header.b="LO3L/M5y"; dkim-atps=neutral Received: from SN4PR0501CU005.outbound.protection.outlook.com (mail-southcentralusazon11011036.outbound.protection.outlook.com [40.93.194.36]) by gabe.freedesktop.org (Postfix) with ESMTPS id D00E810E8E4; Mon, 18 May 2026 15:07:05 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=l7wLLvV1Nk+d8AGiwb1lXu4o38lIcs2oYEHx6jXnpflz2iVwZ7IAag4YWN43ND5nSjkMtbHn8lr1QBZAxGVo4kqDKR1E1MA3exPAPUUZri5pbYBmU+GbrZ7ob6+8Qqe/LGPjvvEarNggsT75Ga/Tg6NquClwWuX8LV9eWYfY1kY5iuBV5nx0MfbToO1DQzYaxqAy7uP4FwaQC0hymE+X3SENhMqwHzMWFUPUUKRY2doGIadJgkTEoZ18JlpOlC93S5E32kmQwoxDlEqtdgAabIi6p4NuQ4Njg1PXm1qGfw3bYQGsDGZF4jcmNkUNxYa+0BsgjcPbt8LHCcNhLwrMTQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=sBAKV68rML2SzmDcrxEnmVCuZ2HbOmy+OYcYF9i09Hc=; b=FjPcbB9fXcPj2GxkpjxLaR0mB4sDoTF0lV9BpYUeiOFFJIA+qNuIN6CDE9UfalG64gTWbbIPLih6hD/zygKkhhP0tWxTBooUdOQC/h3Bph/bVzu1/GOKjdC2XVEqXNR0uJD2m6uOR7KCJfV8cJ+zzBdQTY9ohVtGGlK7p4Z7FCQCf6K6+MNPj2qTXUtV34pWhaFadCpjuYWCV56Qi02hVHPWIM4immwwUtJFDrYaHcX2B+JpDDTrhIZoqcaWgkKKRV8raHKvyne43FDAnDQxuXxYHjrDSbDT29m0C5avcpDzfb8N06uCt4/jX8x7U9xTCDAU8FLS/0aCyj3txQotFw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=sBAKV68rML2SzmDcrxEnmVCuZ2HbOmy+OYcYF9i09Hc=; b=LO3L/M5y7o9KBE+wk9qwDirKgnwdXD1caWyvSYUdKqp+oUzSu05WmEj1awoKxgpnDvTBCTcrFGPxRGibPE/oB7L8FutUa+imknNyMvGn6haQ53Uc0MsRc4HzIygDVNnsvYj5XfgGBTETGRqTKJXKDgtS7R0pRXy0ozoo6eloMbg= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) by SN7PR12MB8059.namprd12.prod.outlook.com (2603:10b6:806:32b::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.25.22; Mon, 18 May 2026 15:06:59 +0000 Received: from PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c]) by PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c%5]) with mapi id 15.21.0025.022; Mon, 18 May 2026 15:06:59 +0000 Message-ID: <15efb253-2171-4436-bf97-0b0d0408e7e2@amd.com> Date: Mon, 18 May 2026 17:06:52 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/12] misc/syncobj: add /dev/syncobj device To: =?UTF-8?Q?Michel_D=C3=A4nzer?= , Julian Orth Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Sumit Semwal , Jonathan Corbet , Shuah Khan , Arnd Bergmann , Greg Kroah-Hartman , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-doc@vger.kernel.org, wayland-devel@lists.freedesktop.org References: <20260516-jorth-syncobj-v1-0-88ede9d98a81@gmail.com> <69dcbcc1-da58-4d34-bfb0-5c8d33b75d59@amd.com> <1162f62e-9c65-446b-9788-bb289a202e6e@mailbox.org> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <1162f62e-9c65-446b-9788-bb289a202e6e@mailbox.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: MN2PR06CA0018.namprd06.prod.outlook.com (2603:10b6:208:23d::23) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|SN7PR12MB8059:EE_ X-MS-Office365-Filtering-Correlation-Id: fd318ded-88c6-442f-3fad-08deb4ef1bad X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; ARA:13230040|366016|376014|7416014|1800799024|18002099003|11063799003|4143699003|56012099003|22082099003|3023799003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:PH7PR12MB5685.namprd12.prod.outlook.com; PTR:; CAT:NONE; SFS:(13230040)(366016)(376014)(7416014)(1800799024)(18002099003)(11063799003)(4143699003)(56012099003)(22082099003)(3023799003); DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?RkpsaUNISExTWU5lNjA4OVJiWDNpbVloWXRmOVRGSVVUMFB4N3R2ZVRpY3M3?= =?utf-8?B?YkhIa0Z5OWJlelJrMllHRGxnSlBSMlc4QWJOeXpTd0F4Wm9xZkNVU3dKbmNM?= =?utf-8?B?TGNwMURacjZ4LzlBOFVEbERKQmY5cW1DOUttOWp1Z1Y3SWUwZkZNbW5scDBn?= =?utf-8?B?UThNeGcxSWd6VXNpYThHZ1A2SlJyMlRmR1ZqWFlMTmc0SjNNS2RvK0QyenBh?= =?utf-8?B?bFVEVnorZ0lTSDFiWFV2bkI2WW0wMUNiRVh4dEdOaVA1QmRhaUtsS3lvbzV0?= =?utf-8?B?VHF2Q2wyNGgzMzNoOWF5czlTOFUySEpIdVpnM3dYNzBIWjVrT054Qm5OSVlu?= =?utf-8?B?M1plNWc4Q3dldEZ6MEY2bHM2V1hQWk5vZit5SUt1S2U1ZzMyVm94ZHpIYnl0?= =?utf-8?B?dTYvN0JCL2dxMXRmV3ZWOXFmVXh2Y01LMzM2WjQ5OU52OXJpbHlXV2hFU1R1?= =?utf-8?B?akVKR1VPQXQ1YXN5WlFrTmUyQ0JVRkdDWTI5cVJxdW8rSFQvVGRZOHlQR1Qr?= =?utf-8?B?UUVCSTZXYmNkRUM5ZTJkc1VSa1dETEpLeXdZTWwzQTEweUpIcjVMbmhoWmZy?= =?utf-8?B?cHdMZ1AzaHRYNUx0L0Q1VlFsRm00V1JRQXdhbHIycDNWR3kvOCtJSzRHK2pI?= =?utf-8?B?RWovUjlOMFdqUFFJY09scjA4YXB6OXZVczJ6bkpvQ0FseTJyTTV0emI0UllB?= =?utf-8?B?b1dvV25mbEJlOTAxeXNITGFCL0w4MEN5Y3JKQlNiaGN2WW1VRUpNeDQvWVE5?= =?utf-8?B?eVFHdEZTd0dLaGRsY3FaMjQvdzFZditkd0ROSXh5cmZNTDlYZU5hQnJrUk1k?= =?utf-8?B?UnVXckloS3YyQ0NBM0R1Y3QyNjJEem85SmdGaGt3Nklmd3p6a1FUZEFYMEgz?= =?utf-8?B?THZhSEVPSmllSWFNTHNJbXBYSE5SY3RmS3FUcG9YcGdJTGNiU3MwcmRMRzZU?= =?utf-8?B?NHR1SWhHOGRVcEpqMFdaSEU3RjdGaTBqRnpkN1FwMHNEWDJyWTRqK0NRYWxl?= =?utf-8?B?V3JRT0dUNllVRzNFK2xPTGV6bVROQS82RnJ1bEtENEhrdUs4UWFjaVRRTEVC?= =?utf-8?B?NGl4ZDFsZk13SVhRb0g5K2FDaVBOV2ROOU9CRExDdGU2V0poRU90cmhPcFgv?= =?utf-8?B?TytWVDAzMm53UUFEQUYvZ0ovODJrMHl1YXg0ZjR2akZQZU1XTUlzRGRZcXNC?= =?utf-8?B?NGM0NitjakJZNEp0N2NKZ2ZVTHEyMU04MnpMS3NGUnJGMnpGQXdXekVCM2lK?= =?utf-8?B?K0RCUm5KcGdrc1NMTTdVUFZOMEZMaHY2SjNKd1RDQ1U3Y3RZSjQ2R2FMcjhk?= =?utf-8?B?Mno1UER5eUhZL3lYT2M5cDN3dFlIN0s3Uy84RXdGQ1N0OGdYa1RsZDNCcjZ4?= =?utf-8?B?ejZ4MzFWbmtqRm5WUFROcWlGc01QWFJwVVkwS1hTMHpCbkdkOENuUDgvVmsx?= =?utf-8?B?aFduNGg3ZFlJY0NuV0dpTlREVWVZUGdVcWpsSEVHRnJyMVNMU0Y2UjFWdFFK?= =?utf-8?B?Ny9NSGJkaWtBY2VXZEZXcGhLMnJJNUxjM0FwUEFTeHVvRkhyb05ZVVFHcGVC?= =?utf-8?B?Qnd3UFpVVVVDcFRydEkwajVpbFdSRlZiNGloSUlJMlRkUHNacVN3U2s4L1Ry?= =?utf-8?B?Zko3SFJTOU13UitVS3UrbDVVWXhmZk4zYS91UmxEb0dtRlZ5RDlsdkh3UlRW?= =?utf-8?B?ajkxRzJieUd5Q3pIS3pUM2FRSy9KaC83SmVxSjBGTTVWaFI1b3FLdTBVN2Fo?= =?utf-8?B?R1M5dk5FRUt5Q0JSeElYcTd3em8xMXlFc290ajV1bitqUXNQUVJBWE5GdTZy?= =?utf-8?B?VXVNZW9MY2JyYlB6dHZxNGRZRW1nSVN2Z3gyRno0aWdMTmgrZlNwbTBVY1ZY?= =?utf-8?B?YzdjUE9MMEg0K21QVHBKZFBVV3NrZnpnazVtcWVpSlB0eEZ4UnBudmNtcGU4?= =?utf-8?B?U0ZPYm53cU9JOE9TUnRkT1p3ekI2N1MxejZOaExnbnJkQjQwUWFTYloxS0JV?= =?utf-8?B?VzloUHorSVVNNmVJeFdtYzREM2h2L000MGMyOThpNy9kY1BOZlFWbWtMZmFX?= =?utf-8?B?bmdnVi9KMHhPU2t6L0NDWTIyY2Vod3pERGNBdmIxcXZjRHJnN2lNa0sydnBB?= =?utf-8?B?Q2pVQlR0TXV1T0l4WGhlc0VySDB6VFNKZ3NremZibDl6TnBpRWxIOVRjSytG?= =?utf-8?B?UU12YzRtTWhNVDlWMVgyZU82ZWZKOHErRFU2eVNzcURMSWMrWm9acDB5Syt3?= =?utf-8?B?TlVqMUtLKzNoeXNybmh6YUx4YmJIaDVDRll3NkxTeGhTUitoQkp0RmROcHR3?= =?utf-8?Q?/HEFmbS5jYNPkPEqGV?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: fd318ded-88c6-442f-3fad-08deb4ef1bad X-MS-Exchange-CrossTenant-AuthSource: PH7PR12MB5685.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 May 2026 15:06:58.9961 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: oiRuQoDUwaEfV1oy5CCosYqHD0aJin7XzUSclP5RGd7fz7j+zadbS1naF01K4rjC X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB8059 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 5/18/26 16:59, Michel Dänzer wrote: > On 5/18/26 14:41, Christian König wrote: >> On 5/18/26 14:02, Julian Orth wrote: >>> On Mon, May 18, 2026 at 1:58 PM Christian König >>> wrote: >>>> On 5/16/26 13:06, Julian Orth wrote: >>>>> This series adds a new device /dev/syncobj that can be used to create >>>>> and manipulate DRM syncobjs. Previously, these operations required the >>>>> use of a DRM device and the device needed to support the DRIVER_SYNCOBJ >>>>> and DRIVER_SYNCOBJ_TIMELINE features. >>>>> >>>>> There are several issues with the existing API: >>>>> >>>>> - Syncobjs are the only explicit sync mechanism available on wayland. >>>>> Most compositors do not use GPU waits. Instead, they use the >>>>> DRM_IOCTL_SYNCOBJ_EVENTFD ioctl to perform a CPU wait. Being tied to >>>>> DRM devices means that compositors cannot consistently offer this >>>>> feature even though no device-specific logic is involved. >>>> >>>> Well the drm_syncobj is a container for device specific dma fences. >>> >>> Not necessarily. The DRM_IOCTL_SYNCOBJ_TIMELINE_SIGNAL ioctl attaches >>> some kind of dummy fence that is already signaled. I don't believe >>> this is device specific. That is also the path that llvmpipe would >>> use. >> >> Yeah I feared that. >> >> This is the wait before signal path and if I'm not completely mistaken that one is not supported by a lot of compositors. > > Where did you get that impression from? Kernel space seems to not handle that support very well. We added the flag at some point for drivers, but only a fraction actually implemented it. I wasn't aware that the general eventfd implementation can handle it, but yeah when compositors use that one then that actually makes sense. > It's arguably the main point of the syncobj Wayland protocol extension, which is supported by all major compositors (except Weston, where it's still a pending MR). > > >> So as far as I can see using drm_syncobj for software rendering really doesn't make sense, eventfd is a much better fit for that use case. > > I agree with Julian's rebuttal to that. That eventfd is missing the timeline functionality is a pretty good argument, but I'm still not sure if that justifies the extra kernel complexity. Regards, Christian.