From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-6.0 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 19BB57D161 for ; Mon, 28 Jan 2019 08:47:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726556AbfA1Ir4 (ORCPT ); Mon, 28 Jan 2019 03:47:56 -0500 Received: from mail-eopbgr60062.outbound.protection.outlook.com ([40.107.6.62]:11808 "EHLO EUR04-DB3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726415AbfA1Ir4 (ORCPT ); Mon, 28 Jan 2019 03:47:56 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cern.onmicrosoft.com; s=selector1-cern-ch; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; 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Received-SPF: Pass (protection.outlook.com: domain of cern.ch designates 188.184.36.46 as permitted sender) receiver=protection.outlook.com; client-ip=188.184.36.46; helo=cernmxgwlb4.cern.ch; Received: from cernmxgwlb4.cern.ch (188.184.36.46) by AM5EUR02FT031.mail.protection.outlook.com (10.152.8.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.1580.10 via Frontend Transport; Mon, 28 Jan 2019 08:47:51 +0000 Received: from cernfe03.cern.ch (188.184.36.39) by cernmxgwlb4.cern.ch (188.184.36.46) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 28 Jan 2019 09:47:49 +0100 Received: from pcbe13614.localnet (2001:1458:202:121::100:40) by smtp.cern.ch (2001:1458:201:66::100:14) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 28 Jan 2019 09:47:50 +0100 From: Federico Vaga To: Vinod Koul Reply-To: CC: , , Subject: DMA Engine Documentation: TX Descriptor and Submission Date: Mon, 28 Jan 2019 09:47:50 +0100 Message-ID: <1655406.8MLMLfCWyH@pcbe13614> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; 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Clients get a TX descriptor from a DMA engine using things like `dmaengine_prep_*`. These calls - may - allocate new descriptors and return them to the caller; this may include other structures which are not visible to clients. So, if my understanding is correct, this means that it's the DMA engine that, on TX completion, releases any TX descriptor allocated by `dmaengine_prep_*`. This implies that the pointer that the client is using must be considered invalid right after `dmaengine_submit()`. If what I understood by reading the documentation and the code is correct, then I think that this should be mentioned in the Documentation. If I'm wrong, please tell me where :) Thanks